A Comparison of U.S. Mining Industry Criteria for Intrinsically Safe Apparatus to Similar IEC-Based Standards

Authors

Gerald Homce, Joseph Waynert, Michael Yenchek, and R.J. Matetic

Abstract

Electrical and electronic equipment intended for use in potentially explosive atmospheres in U.S. underground mines must conform to and be approved under Mine Safety and Health Administration (MSHA) construction and testing criteria, such as those specified for intrinsically safe (IS) equipment in the MSHA Approval-Criteria document ACRI2001. MSHA does not currently recognize IS certifications based on other criteria, such as those found in consensus standards employed by other U.S. industries, or those used in other countries. The National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Mining Research Division (PMRD) explored the assertion that accepting the use of equipment certified to outside standards would expand the quantity, diversity, and capabilities of equipment available to U.S. mines, and thus better serve mineworker safety. Specifically, this research studied the potential benefits and safety issues associated with acceptance of portable electronic devices certified to International Electrotechnical Commission (IEC)-equivalent IS standards, for use in U.S. underground coal mines. The study first identified 59 IEC-certified and one Atmosphères Explosives (ATEX)-certified portable IS devices that meet IS criteria approximately equivalent to ACRI2001, but are not also MSHA-approved. Of these 60, three have functions and capabilities not found among MSHA-approved devices. Research next compared individual criteria in ACRI2001 to corresponding provisions in the American National Standards Institute/International Society for Automation (ANSI/ISA) standards 60079-0 and 60079-11, which are the U.S.-adopted versions of IEC 60079-0 and 60079-11 (the IEC standards relevant to intrinsic safety). The comparison identified 28 individual technical topics for which ACRI2001 requirements appear more restrictive than their ANSI/ISA counterparts. Eleven of the 28 were deemed substantive, but it could not be conclusively determined if they would have a material effect on the level of safety provided. Finally, the study evaluated the safety histories of ACRI2001 in the U.S., and IEC IS standards as applied in the mining industries of Australia and South Africa, and found both ACRI2001 and IEC standards to be effective.

1. Introduction

This paper documents findings of a study by the National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Mining Research Division (PMRD) examining potential benefits and safety issues associated with acceptance of portable electronic devices certified to International Electrotechnical Commission (IEC) intrinsic safety (IS) standards, for use in U.S. underground mines. Specifically, this refers to the use of such IEC-certified devices in applications currently requiring Mine Safety and Health Administration (MSHA) approval. The research included three investigations: 1) a review of IS portable equipment for underground mining, to identify technologies not currently available to U.S. mines, 2) a detailed comparison of MSHA IS criteria and IEC-based IS standards to identify differences, and 3) a comparison of the safety histories for MSHA IS approval criteria and IEC IS standards as used for portable equipment in mining.

2. Background

Electrical and electronic equipment used in underground mines with potentially explosive atmospheres should be designed and tested in accordance with specific recognized safety criteria. Coal mines are the most common example, where the hazards are explosive methane-air atmospheres and accumulations of coal dust.  In the U.S., Title 30 - Code of Federal Regulations (30 CFR) mandates that electrical and electronic equipment used in underground mines in potentially explosive atmospheres be permissible, that is, issued a formal approval for such use by MSHA (30 CFR, 2016a).  In most cases this equipment is constructed to either explosion-proof or IS criteria as defined by MSHA.  Explosion-proof (XP) enclosures are characterized by heavy wall construction and specialized joint and seal designs so that an ignition of gas inside an enclosure cannot propagate to the atmosphere outside.[1]  IS circuits are designed so that any sparking or heating under normal or fault conditions cannot supply sufficient energy to ignite an explosive atmosphere.  MSHA IS requirements are detailed in the document Criteria for the Evaluation and Test of Intrinsically Safe Apparatus and Associated Apparatus, designated as ACRI2001 (MSHA, 2008).[2]  30 CFR Part 6, Testing and Evaluation by Independent Laboratories and Non-MSHA Product Safety Standards, allows MSHA to also approve mining products designed to non-MSHA product safety standards, provided MSHA determines that the standards used provide at least the same degree of protection as MSHA requirements or can be modified to provide at least the same degree of protection (30 CFR, 2016b). MSHA currently however, does not recognize non-MSHA construction and testing criteria for IS electronic equipment.

Outside the U.S., portable electronic equipment used in potentially explosive atmospheres, including underground mining applications, is often designed to meet standards issued by the IEC, or country-specific standards based on IEC requirements. IEC IS construction and testing criteria are found in the standards IEC 60079-0 Explosive atmospheres - Part 0: Equipment - General Requirements (IEC, 2011a), and IEC 60079-11 Explosive atmospheres - Part 11: Equipment protection by intrinsic safety “i” (IEC, 2011b).  Many countries adopting their own IEC-based standards do so with the intention of gradually transitioning to, or harmonizing with, the original IEC requirements, such as Australia which currently uses AS/NZS standards differing from the IEC in name only.  In the U.S., IEC-based standards applicable to equipment used in potentially explosive atmospheres in industries other than mining, have been published as American National Standards by the American National Standards Institute (ANSI).  At the time of this study, ANSI IS standards were issued jointly by the International Society of Automation (ISA) and Underwriters Laboratories (UL) as ANSI/ISA 60079-0 and ANSI/UL 60079-0 (ANSI/ISA, 2009a) (ANSI/UL, 2009a), and ANSI/ISA 60079-11 and ANSI/UL 60079-11 (ANSI/ISA, 2009b) (ANSI/UL, 2009b).  These U.S.-adopted versions include national differences, that is, U.S.-specific revisions to the original IEC standard.

The hypothesis on which this study was based suggests that accepting portable electronic devices certified to IEC IS standards, for use in U.S. underground mines, may enhance overall mine safety by increasing the quantity, diversity, and capability of the equipment available to mine operators. Technology affected could include communications, personnel tracking, portable instrumentation, information systems, and emergency/disaster response equipment.  Such acceptance would be technically possible under 30 CFR Part 6, and does have proponents among mine operators and equipment manufacturers.  The presumption is that in the near term IS equipment currently available with IEC certification, but not currently MSHA-approved, would become available for use in U.S mines.  In addition, the introduction of new and innovative technology for underground mines would be enhanced in the future by making the U.S. mining industry a more accessible market for companies that design and manufacture specialized equipment for explosive atmospheres.  Factors sometimes cited to support the latter potential benefit include widespread global familiarity and acceptance of IEC standards, numerous approved laboratories for testing and IEC certification, availability of private companies to assist with product design and the certification process, regular reviews and updates of IEC standards to accommodate rapidly changing technology, and the ongoing development of the IECEx (IECEx, 2016), a global explosion-protection standard conformity assessment (quality control) system.

Countering the above assertions, there are potential concerns surrounding the acceptance of IEC IS certification, such as verifying the adequacy of the IEC standards as compared to current MSHA criteria, and ensuring the quality, credibility, and impartiality of the labs and certifying bodies involved[3].  Further, the proposed improvements in IS equipment availability and advantages for approval-process access and efficiency may not be realized, or may not be as significant as anticipated.  Notwithstanding these issues, the potential advantages warrant investigating the acceptance of IEC or IEC-based IS standards for U.S. mines.

2.1 Scope of study

The study described in this paper focused only on portable IS equipment for use in U.S. mines, in applications where MSHA-approved equipment is currently required.  Portable equipment is defined as equipment that is self-contained and is person-wearable, hand-held, or can readily be carried by one person.  This limitation was applied due to differences in the way MSHA and IEC standards address IS systems such as mine-wide communications or atmospheric monitoring systems with numerous hard-wired interconnected components (as opposed to IS portable devices).  MSHA approves individual devices and system components, as well as entire systems, using ACRI2001.  Under IEC standards, design and testing of IS devices and system components conform to IEC 60079-0, and IEC 60079-11.  For IS systems under the IEC, however, these two standards are supplemented and in some cases superseded by the standard IEC 60079-25 Explosive Atmospheres – Part 25: Intrinsically Safe Electrical Systems.  The IEC approach allows more flexibility with respect to how and by whom an IS system is created and how it is evaluated; however, attempting to address these differences would have significantly complicated the detailed comparison of criteria for MSHA approval and IEC certification.

In addition to considering only portable equipment, the study focused solely on IEC criteria that are most nearly equivalent to MSHA IS construction and testing criteria.  In the U.S., 30 CFR explicitly specifies underground coal mine locations that require the use of permissible electrical and electronic equipment, that is, equipment approved by MSHA for use in potentially explosive atmospheres.  Examples of locations requiring permissible equipment are areas inby the last open crosscut, areas within 150 ft of pillar workings or longwall faces, and return air courses[4].  Locations other than those so specified in 30 CFR generally do not require equipment to be permissible, effectively dividing areas in U.S. underground coal mines into two hazard categories.  Exceptions to this requirement are certain types of mine monitoring and communications equipment that must be permissible when operating on back-up power, irrespective of their location, if they are expected to remain operational after mine ventilation has been compromised (30 CFR, 2016c).  In contrast, management of explosion risk in underground coal mines in other countries is often more complex, sometimes defining levels or categories of explosion risk lower than that associated with permissibility in U.S. mines.  This creates legitimate mining applications (outside the U.S.) for equipment certified (by design) at lower levels of explosion protection than that provided by MSHA IS approval criteria, such as less restrictive IS criteria, flameproof construction, or increased safety techniques (Magison, 1998).  Such equipment was not considered in this study.

Among other coal producing countries, examples can be found where mine safety regulations place more responsibility on mine operators, than is the case in the U.S., for identifying and characterizing underground mine locations presenting explosion risk. In some respects, this approach is similar to that common in other industries where explosion-risk areas are classified based on the type and level of hazard, the physical environment, and a risk analysis.  Explosion-protected electrical and electronic equipment with certifications suitable for those classifications, is then required for such areas.  The international standards IEC 60079-10 and IEC 61241-10 provide guidance for the classification of gas/vapor and dust explosion hazard areas, although their scopes exclude underground mining.  Explosion risk classification guidelines for mining (differing from those used in the U.S.) do exist, however, in standards and regulations of some coal producing countries.

An example of detailed hazardous area classification guidelines for mining is found in the Queensland, Australia Coal Mining Safety and Health Regulation (Queensland, 2012). This regulation requires each underground coal mine operator to establish and identify explosion risk zones (ERZs) for all locations at their mine by performing a risk assessment based on absolute methane levels, work activities, and location within the mine, as well as foreseeable events and failure modes.  The provisions specify three potential zones, including ERZ0 (ERZ zero) where methane levels are known or likely to be over 2%, ERZ1 for methane levels from 0.5% to 2%, and NERZ which designates a negligible explosion risk for zones with methane levels below 0.5%.  In addition to zone assignments according to methane concentrations known or likely to be present, certain locations must be assigned a minimum risk level of ERZ1 irrespective of methane concentration, such as working faces, intake entry areas inby the last open crosscut, return air courses, mined-out areas, areas with poor airflow, and locations where methane drainage systems are being installed or maintained.

Once ERZs have been assigned for all locations, the selection of electrical and electronic equipment is dictated primarily by the ERZ in which it will be used. For example, IS portable equipment used in an ERZ0 must be certified to what is effectively an IEC explosion-protection rating of Ex ia I, which meets criteria most nearly equivalent to those used for MSHA IS approval.[5]  An ERZ1 presents less risk, and equipment used there can be certified to explosion-protection construction and testing criteria that provide a lower level of IS protection than that required for an ERZ0.  For example, an IS device IEC-certified as Ex ib I would be acceptable in an ERZ1.[6]  Similarly, equipment permitted in areas designated NERZ do not necessarily need an explosion-protection certification as is required for ERZ1, but must still meet minimum construction requirements with respect to suitability for underground mine use, primarily protection from dust and moisture.  Such an approach thus defines two zones and levels of equipment requirements (ERZ1 and NERZ) that do not exist in U.S. underground coal mines, and as noted earlier in this section, this creates applications for mine-duty equipment certified to IS explosion protection levels that provide a lower level of protection than the criteria used for MSHA permissibility.

The approach just described for Queensland, Australia, also imposes other provisions upon a mine operator that are not required in the U.S.—for example, requirements to clearly post the ERZ boundaries underground, maintain and display a plan showing the boundaries, and update the plan at the end of each shift. Also, automatic methane monitors must be in place at certain ERZ boundaries and conform to specific requirements for visible alarms and automatic de-energizing of electrical circuits.

The foregoing discussion is not intended to portray the explosion protection approach used in Queensland as preferable to that used in the U.S., but rather, to highlight the significant differences with such a system, and the influence such differences have on the application of IEC-based IS standards.

2.2 Standards updates

The research described in this paper was completed in 2012, and was based on the most current relevant regulations, standards, criteria, and records available at that time. At this writing, much of that information is still current and valid, such as the MSHA IS criteria document ACRI2001, as well as the standards IEC 60079-0 and IEC 60079-11. Some sources however, have been updated, most notably the standards ANSI/ISA and ANSI/UL 60079-0, and ANSI/ISA and ANSI/UL 60079-11, 5^th Editions, 2009, for which the 6^th Editions were released between late 2012 and 2014 (ANSI/ISA, 2012a) (ANSI/ISA, 2012b).[7] Although the 5^th Editions retain “active” status until September 1, 2018, and most provisions remain unchanged in the 6^th Editions, there are some specific 6^th Edition revisions that should be noted in the findings presented in this report. Where this is the case, the updated information will highlighted in a light gray box with the notation Update. This notation will also be used for other relevant information that became available since the study was completed. In this way, a clear, accurate description of the original research and findings can be provided without omitting important updated material.

[1] XP equipment and approval criteria were not included in this research.

[2] ACRI2001 is a designation conforming to an internal MSHA document control system that identifies it as an “A”pproval “CRI”teria document, for which “20” indicates the Electrical Safety Division of MSHA’s Approval and Certification Center, and “01” the document’s number in a series. The first edition of ACRI2001 was released in 1995, with revisions in 2000 and 2008. Conformance with ACRI2001 requirements indicates compliance with 30 CFR intrinsic safety requirements, but all other applicable 30 CFR requirements must also be met before an MSHA approval will be issued.

[3] Under 30 CFR Part 6 - Testing and Evaluation by Independent Laboratories and Non-MSHA Product Safety Standards, MSHA requires written evidence of an outside laboratory's independence and current recognition by a laboratory accrediting organization.

[4] The terminology inby the last open crosscut, pillar workings, and longwall faces, all refer to locations in underground coal mines that, because of their proximity to active coal extraction, are likely to have methane liberation and/or dust generation. Return air courses are mine entries (excavations) used to carry air that contains some level of methane and/or dust out of the mine.

[5] An IEC certification of Ex ia I denotes an ia level of intrinsic safety (the highest level of IS protection, requiring testing with up to 2 faults) and Group I (equipment intended for gassy underground mining applications).

[6] An IEC certification of Ex ib I denotes an ib level of intrinsic safety (ib requires only single-fault testing, providing a lower level of protection than ia).

[7] Shortly after the completion of this study, ISA standards development work under the ISA12 Standards Committee and Subcommittees (Electrical Equipment for Hazardous Locations) was transferred to Underwriters Laboratories Inc. (UL) under UL Standards Technical Panel (STP) 60079. ISA will no longer issue standards dealing with electrical equipment for hazardous locations.

3. Review of IS portable equipment available for underground mines

The investigation of IS portable equipment availability for mines first compiled a list of currently available MSHA-approved portable IS equipment, and then identified IEC-certified portable devices that meet IS criteria most nearly equivalent to those for MSHA approval, but are not also MSHA-approved (and so are not permitted to be used in gassy underground U.S. mines). The MSHA-approved and IEC-certified equipment were then compared to identify IEC-certified devices that represent technology or capabilities not currently available to U.S. mines.

3.1 Material and methods (Review of IS portable equipment available for underground mines)

3.1.1 Identifying currently available MSHA-approved portable IS devices

The MSHA Approval and Certification Center (A&CC) evaluates and tests mining products intended for use in underground coal and other gassy underground mines for compliance with federal regulations. Upon successful completion of evaluation and testing, MSHA issues an approval authorizing a manufacturer to produce and distribute the product for use in mines (MSHA, 2016a).  MSHA maintains a complete list of approved products on its web site, categorized by the 30 CFR regulatory Part number under which they were evaluated (MSHA, 2016b).  Products of interest for this study, specifically portable permissible devices, were identified in 5 categories in the MSHA-approved product list.  The MSHA listings do not indicate current availability of the equipment however, so each item within the 5 categories was investigated further, and only those currently commercially available were included in the study.  Listed in Table 1 are the 30 CFR Part number and name for each category reviewed from the MSHA listings, and the number of devices ultimately found to be currently available.[1]  Examples of approved devices under the categories listed are gas detectors, dust samplers, noise dosimeters, multimeters, mobile equipment remote controls, radio transceivers, personnel tracking devices, flashlights, and cap lamps. 

30 CFR Part number and category name	MSHA-approved portable IS devices currently commercially available
Part 18 – Instruments	85
Part 19 – Electric Cap Lamps	10
Part 20 – Flashlights	26
Part 22 – Methane Detectors (portable)	11
Part 23 – Communications and Tracking	75
Total	207

Table 1. MSHA-approved portable IS devices currently commercially available.

3.1.2 IEC certification of portable IS devices; concepts, terminology, and labeling

Searching for IEC-certified portable IS devices potentially suitable for use in U.S. coal mines requires a clear understanding of IEC explosion protection standards. The MSHA IS criteria document ACRI2001 focuses on a narrow set of hazards, specifically, methane/air atmospheres and coal dust, and includes IS testing criteria that require the application of up to two simultaneous faults.  In comparison, IS standards issued by the IEC are significantly more complex to account for a wide range of conditions within many different industries, numerous hazard types and severities, and different levels of protection.  As a result, it is necessary to understand what small subset of IEC-certified IS devices are intended for potentially gassy and dusty underground mines, and further, which of these would be most nearly equivalent to MSHA-approved IS devices.

Under the IEC and similar standards systems, explosion hazards are defined in terms of the hazard type and the likelihood of the hazard being present. This is accomplished by using a Group to identify the hazardous substance present, which indicates the ignition energy required, a Zone to describe the likelihood a hazard is present (not directly equivalent to the zones previously defined under Queensland, Australia, mining regulations, in section 2.1), and a Temperature Class to account for ignition from hot surfaces. Mines susceptible to firedamp (methane in air) are unique within this structure, in that they alone are designated Group I.  IEC 60079-0 (2011) Section 4.1 states that, The types of protection for Group I take into account the ignition of both firedamp and coal dust along with enhanced physical protection for equipment used underground—that is, Group I indicates that the hazards present are methane in air and coal dust.  Group I devices can be applied in different Zones within the mining environment, such as Zones 0 and 20 (gases/vapors and dust, respectively), indicating that the hazard is present continuously or for long periods of time under normal operating conditions, or Zones 1 and 21 (gases/vapors and dust, respectively), indicating that the hazard is likely to occur during normal operating conditions, but less likely to occur than in Zones 0 and 20.  The maximum component surface temperatures for Group I are specified directly in IEC 60079-0 (2011) Section 5.3.2.1, being 150°C if coal dust can form a layer on the surface, or 450°C if coal dust is not likely to form a layer on the surface. 

The types and levels of equipment explosion protection techniques permitted for a given application are in large part dictated by the Zone, that is, the probability of a hazard being present. For Group I equipment under IEC standards, the Zones in question allow a range of protection techniques, such as intrinsic safety, encapsulation, and flameproof construction.  With respect to intrinsic safety, IEC 60079-11 specifies three levels of protection, identified as ia, ib, and ic.  Level ia is characterized by the most protective IS criteria, including testing with up to two simultaneous faults, and is required for Zones 0 and 20.  As noted previously (section 2.1) the ia level of intrinsic safety would be the specific IEC IS certification most nearly equivalent to MSHA intrinsic safety approval.  Referring back to the Queensland, Australia, explosion risk zone system detailed earlier (section 2.1), the highest risk zone, ERZ0, would effectively require IS-equipment certified as ia.  Level ib has some criteria that are less protective than those under ia, including testing with only up to one fault, and is the minimum level of IS protection required for IEC Zones 1 and 21.  An ib level would be acceptable for an ERZ1 in Queensland (ERZ1 has lower risk than ERZ0), but neither ib nor ERZ1 have counterparts in MSHA IS approval criteria or related regulations for U.S. mines.  Level ic is less protective than ib, with the most notable difference being elimination of a safety factor for circuit evaluation and testing.  An ic certification would be one option for complying with requirements for equipment in an NERZ area in Queensland (negligible explosion risk), but as with the ib certification, ic has no counterpart in MSHA IS approval criteria.  Under IEC standards, a portable IS device may also be assigned (currently optional) an equipment protection level (EPL) which is a rating based on the overall likelihood that the device will become a source of ignition.  The EPL levels Ma and Mb indicate Group I (mining) applications, with Ma denoting a very high protection level, including an IS certification of ia, and Mb indicating a high level of protection, where an IS certification of ib would be acceptable.[2]

The foregoing discussion shows that IEC IS certification of equipment for underground mines provides for different levels of protection that have applications under explosion risk management schemes such as the ERZ system employed in Queensland, Australia. As has been explained earlier however (section 2.1), the focus of this project confines our interest to equipment with IEC IS certifications that are most nearly equivalent to MSHA approval of IS portable devices.  Such equipment would at a minimum carry an IEC certification of Ex ia I, where Ex identifies explosion protection, ia indicates intrinsic safety at an ia level per IEC 60079-11, and I denotes Group I.

3.1.3 Identifying IEC-certified IS portable devices that meet criteria most nearly equivalent to those for MSHA approval, but are not also MSHA-approved

The IECEx, a global standard conformity assessment system administered by the IEC, maintains an international database of products IEC-certified for use in explosive atmospheres.[3]  That database was searched in this effort, as well as other sources including IS equipment manufacturer and supplier product listings, and databases maintained by organizations in foreign countries.  The IECEx database contains listings for equipment employing many different types of protection for use in explosive atmospheres, including over 9,300 devices conforming to the IEC intrinsic safety standard.  When narrowing the search however, to just portable equipment with certifications most nearly equivalent to MSHA IS approval, 59 devices were identified that did not also have MSHA approval.  These 59 devices are certified as Ex for explosive atmospheres, intrinsically safe at an ia level, and Group I (suitable for mines).[4]  The reason for such a dramatic reduction in the number of available devices is the wide range of applications and protection levels covered by the original 9,300+ IS devices.  Compared to the single Group and single IS level (ia) covered by the 59 devices, the larger total includes certifications representing three different Groups (with the vast majority for non-mining applications), three classes of flammable gas, three classes of combustible particulates, three levels of intrinsic safety criteria, six temperature classes, and eight equipment protection levels.

ATEX is another certification system that was commonly encountered during this review. ATEX (ATmosphères EXplosives) was instituted to offer one unified compliance procedure accepted by all European nations, and while the IS standard recognized within ATEX is technically the same as under the IEC, terminology and labeling differ.  Although a number of devices were identified as having an ATEX IS ia certification appropriate for underground mines, all but one were duplicates of devices found in the IECEx database (i.e., most are devices having both IEC and ATEX certification).  This brought the total number of individual devices identified to 60.  Each of the 60 devices identified can be placed into one of seven functional categories listed in Table 2.

Functional category	Number identified
Imaging	1
Mobile computing	1
Analysis and measurement	23
Communications	16
Tracking	7
Lighting and alarms	9
Miscellaneous	3
Total	60

Table 2. Number of IEC/ATEX-certified IS devices identified, listed by functional category.

3.2 Results and discussion (Review of IS portable equipment available for underground mines)

The list of 60 IEC or ATEX-certified products was compared against the list of available MSHA-approved portable IS devices, to identify IEC/ATEX-certified devices for which no MSHA-approved counterpart exists to perform the same function.  Three such devices were found, including a digital camera (Extronics iCAM501 Ultra), a personal digital assistant (PDA) (ecom i.roc 623; ATEX certified), and a laser bar code scanner (Intermec Technologies CK32IS; actually an IS mobile computer).

3.2.1 Potential benefits of broadening technology available for use in U.S. underground coal mines

Although this task identified only three portable IS devices IEC-certified as Ex, ia, I, that offer capabilities not found in currently available MSHA-approved IS portable equipment, they can serve as examples of the potential health and safety benefits of improving and expanding portable-device technology available for use in U.S. underground coal mines.  The following discussion presents possible benefits of the technologies embodied by the three devices identified.

Digital camera (imaging): Digital imaging (both still and video) is a good example of technology that has been in common use for many years, but has seen delayed entry into the underground coal mining environment due to a lack of appropriately-approved cameras or other devices with digital imaging capabilities. The benefits of digital imaging are the ability to quickly and easily capture, process, view, and transfer still or video images.  Possible applications at mining operations include: more easily documenting safety-related issues or environmental conditions, use of zoom capabilities to help personnel avoid approaching dangerous areas for initial inspection or documentation, creating customized site-specific safety training aids, enhancing record-keeping and inspection accuracy and accountability, use for operational functions such as quickly supplying enhanced, detailed information to management, and use as an infrastructure and equipment maintenance aid.

Personal digital assistant (PDA) (mobile computing): Personal digital assistants (PDAs)—small mobile devices that serve primarily as personal information managers—have seen extensive use in many different applications over the last 20 years. They have been valuable tools in operations, maintenance, logistics, and support activities in many industries, being used for tasks such as controlling inventory, creating and managing maintenance records, tracking shipments, and operational or safety inspections.  Their versatility is further enhanced by the ability of some PDAs to run specialized versions of common software packages, be linked to personal computers, provide internet and Bluetooth connectivity, and serve as platforms for custom software.  Such capabilities could serve many functions in underground coal operations, directly and indirectly helping to improve mineworker health and safety.  Examples include: improving the speed and accuracy of data entry and retrieval for safety-related inspections; equipment inventory, training, and record-keeping; allowing interaction with wireless local area networks, monitoring systems, or instrumentation for communication or data collection and analysis; and supporting everyday operations and maintenance activities.  Many of the capabilities just described are now available on smart phones, which in many applications have replaced PDAs, but similar benefits would accrue irrespective of the mobile computing device used (assuming approved/certified equipment is available).

Bar code scanner (tracking): Another technology that has been employed in many other industries for decades is the use of bar codes coupled with the scanners used to read them. As a technique that can greatly improve the speed and accuracy of data collection tasks, code scanning technology could be extremely useful for safety or maintenance-related inventories, audits, and inspections at an underground mine. The ease with which a large amount of data can be made available is also a powerful feature of current code scanning technology (employing two-dimensional codes), allowing simple access and use of information such as expiration date, date of last inspection or maintenance, proper location, inventory rotation, or replacement data. Scanners can be stand-alone devices with memory and data processing capability, or peripheral devices used in conjunction with mobile computing devices.

[1] This description means currently available at the time of the study; approximately mid 2012.

[2] An EPL of Ma should not be confused with the IEC encapsulation technique designation of ma.

[3] The IECEx has been issuing Certificates of Conformity for equipment to be used in explosive atmospheres since 2003.

[4] Items that were accessories or attachments for an IS device, but had their own IECEx certification, were not included.

4. Comparison of ACRI2001 and IEC-based IS standards

ACRI2001criteria and the closest corresponding requirements in applicable IEC-based standards were compared to identify and characterize differences. The comparison focused on requirements that apply to portable devices, and identified provisions for which ACRI2001 and IEC-based standards are equivalent, differences where ACRI2001 criteria are less restrictive, and differences where ACRI2001 criteria are more restrictive or cannot be effectively compared.  Differences for which ACRI2001 provisions are more restrictive or cannot be effectively compared were more closely analyzed to assess the potential impact on the level of safety provided.

4.1 Material and methods (Comparison of ACRI2001 and IEC-based IS standards)

As previously noted (section 2.) MSHA IS requirements are detailed in the document ACRI2001, Criteria for the Evaluation and Test of Intrinsically Safe Apparatus and Associated Apparatus.  The 2008-11-04 version of ACRI2001 served as the reference for this IS criteria comparison.  Also as previously explained (section 2.) ANSI standards issued jointly by the ISA and UL are the U.S.-adopted versions of IEC standards available for certifying IS equipment in industries other than mining in the U.S.  The specific documents used for this comparison were ANSI/ISA-60079-0 (5^th Edition, 2009) Explosive atmospheres - Part 0: Equipment - General Requirements, and ANSI/ISA-60079-11 (5^th Edition, 2009) Explosive atmospheres - Part 11: Equipment protection by intrinsic safety “i”.  These documents were derived from IEC standards bearing the same titles, and although most of the language is identical to that in the IEC standards, the ANSI/ISA versions have been modified with U.S. national differences.  Among these differences are the removal of mining-related (Group I) criteria, due to MSHA having jurisdiction over mining in the U.S.  The absence of Group I criteria, however, created a paradox for the subject comparison to ACRI2001, so in order to emulate an IEC-based standard appropriate for U.S. mining applications, the removed mining-related criteria were treated as if they were still part of the ANSI/ISA standards (this was possible because U.S. national differences are indicated in the 2009 ANSI/ISA documents as clearly identified additions and deletions in the text).

The comparison of ACRI2001 and ANSI/ISA IS standards was carried out by a team including four NIOSH researchers, two contracted consultants with extensive mine electrical safety backgrounds, an MSHA subject matter expert (SME) specializing in electrical and electronic equipment approvals for U.S. mines, and four contracted SMEs having extensive experience with ANSI/ISA standards certifications for electrical and electronic equipment. The contracted ANSI/ISA SMEs represented Underwriters Laboratories, Factory Mutual Approvals, Intertek Testing Services NA, and QPS Evaluation Services.[1]

Using ACRI2001 as the baseline, the first step of the comparison involved excluding all sections that are not relevant for portable IS devices.  Then, remaining ACRI2001 sections were reviewed individually so that the most closely corresponding ANSI/ISA sections could be identified and correlated.  Next, ACRI2001 sections effectively equivalent to corresponding ANSI/ISA requirements, and ACRI2001 sections less restrictive than corresponding ANSI/ISA requirements, were identified.  ANSI/ISA provisions in these two groups should be no less effective than those in ACRI2001, and so were not further studied.  The remaining ACRI2001 sections are those that appear to be more restrictive than their ANSI/ISA counterparts, or where a direct comparison is impractical due to differences in approach.  These sections were examined in greater detail to characterize the nature and significance of the ANSI/ISA differences.  After grouping these ACRI2001 sections (those more restrictive than or not readily compared to ANSI/ISA) according to the technical issues they address, those issues were ranked based on their potential impact on the level of safety provided.

4.2 Results and discussion (Comparison of ACRI2001 and IEC-based IS standards)

ACRI2001 is made up of 362 individually numbered sections that contain requirements or criteria against which corresponding ANSI/ISA 60079-0 and 60079-11 provisions were compared.[2]

Sixty-eight sections within ACRI2001 that deal with topics not relevant to portable IS devices were excluded from consideration in this study. The topics generally involve the use of line power instead of batteries, connection of IS and non-IS circuits in a multi-component system, or applications where devices are also covered by criteria other than ACRI2001.  Specific examples include the evaluation of transformers used as protective components (line power interfaces), limits on safe-area voltage levels (non-IS components of a system), and encapsulation when used as an alternate form of protection (covered by ACRI2010).

Of the ACRI2001 sections applicable to portable IS devices, 188 have corresponding provisions in ANSI/ISA IS standards that are effectively equivalent. In some cases there is identical language in ACRI2001 and the ANSI/ISA standards, while in others, the equivalent requirements must be interpreted based on provisions identified in multiple ANSI/ISA sections.  Additionally, 44 ACRI2001 sections are less restrictive than corresponding provisions in ANSI/ISA IS standards, including sections that cover safety factors, allowable component surface temperatures, and some aspects of creepage and clearance distances.  The ANSI/ISA requirements and criteria in these latter two subsets (those equivalent to ACRI2001, and those for which ACRI2001 is less restrictive), should individually be at least as effective as those in ACRI2001 at preventing gas or dust ignition by portable electrical and electronic devices, and therefore were not analyzed further.

Of the ACRI2001 sections applicable to portable IS devices, 66 are more restrictive than the corresponding provisions in ANSI/ISA IS standards, or have requirements and criteria that cannot be effectively compared to their ANSI/ISA counterparts. Because the ANSI/ISA provisions in question, when considered individually, may appear to be less effective than ACRI criteria at preventing gas or dust ignition by portable electrical and electronic devices, they were studied in detail.  To aid in the analysis, the 66 sections were grouped into 28 distinct technical topics, each addressing some specific aspect of IS device design or testing.  The analysis results are presented below, with an entry for each topic providing a short description of the issue, the specific ACRI2001 and ANSI/ISA sections involved, and a short explanation of the nature, extent, and significance of the differences.  Where appropriate, input from the SMEs is also included.  In some cases the differences between ACRI2001 and ANSI/ISA requirements can be clearly defined and quantified, while in others they are much less distinct.  In a few cases, the criteria are so dissimilar that a direct comparison was not possible.

While this detailed evaluation clearly characterized the differences in question, it also revealed that the findings did not allow a definitive, quantifiable determination of the impact each would have on the overall level of safety provided. Such was the case even with investigation of the technical basis for the requirements (when available) and after soliciting additional input from the standards experts involved.  As a result, a more general approach (to assessing impact on the level of safety) was taken, under which NIOSH researchers ranked the potential impact on safety by placing each of the 28 topics into one of two categories as described below.

4.2.1 Category I - Topics for which the ANSI/ISA deviations from ACRI2001 are substantive, but it is not clear if they would have a material effect on the level of safety provided

Although the effect of these deviations on IS device safety is not clear, the issues involved warrant more consideration and possibly further research.  Topics 1 through 11 in the list below (involving 31 ACRI2001 sections) are in this category.

1. ACRI2001 has specific, special spark testing procedures for evaluating circuits operating at over 24V and/or 60Hz, but ANSI/ISA standards do not specify special procedures for such circuits

ACRI2001 10.1.6 through 10.1.6.4.3 (8 sections)                  ANSI/ISA 60079-11  B.1.6

ACRI2001 specifies different spark test procedures and spark test apparatus calibration procedures for evaluating circuits over 24 V and/or over 60 Hz, specifically, adding an additional circuit test and calibration using copper electrodes and discs. ANSI/ISA does not require additional or different testing and calibration specifically for higher voltages or frequency, but does recommend upper limits of 300 V and 1.5 MHz for spark test apparatus.  The ANSI/ISA SMEs queried either feel that the extra procedures are unnecessary, or only note that testing of higher voltage and frequency circuits is rare.

2. ACRI2001 prohibits using alternate test gas mixtures to introduce a safety factor in spark testing, but ANSI/ISA standards allow using alternate test gas mixtures

ACRI2001 10.1.2                    ANSI/ISA 60079-11  10.1.4.2

ACRI2001 does not permit the use of an alternate test gas to attain the required safety factor for spark tests, in lieu of increasing energy at the test point to achieve a safety factor (the alternate test gas is selected to be more easily ignited than methane, and thus yield a safety factor). ANSI/ISA does allow the use of an alternate test gas to attain the required safety factor for spark tests, if increasing circuit energy is not practical.  For the ANSI/ISA SMEs queried, experience with the use of alternate gases for testing at their laboratories ranges from rarely to 25% of all tests, but none indicated concern about the validity of the approach.

3. ACRI2001 has spark testing criteria that are more restrictive than ANSI/ISA spark testing criteria, with respect to the number of test apparatus revolutions required

ACRI2001 10.1.5.3                 ANSI/ISA 60079-11  10.1.4.1

Criteria for conducting spark tests include the number of revolutions to be used for specific types of tests. ACRI2001 requires 1000 revolutions for ac tests, and 1000 for dc tests with 500 revolutions at positive polarity and 500 at negative polarity.  ANSI/ISA also requires 1000 revolutions for ac tests, but only 400 for dc tests with 200 revolutions at positive polarity and 200 at negative polarity.  All ANSI/ISA SMEs queried feel that the use of 1000 total revolutions for ac circuits, vs. 400 total for dc circuits (under ANSI/ISA), compensates for the probability that, on ac tests, some number of sparks will occur at an instantaneous value less than the nominal rms value, whereas the 400 total revolutions for dc circuits will always create sparks at the full nominal value.  This implies that 400 revolutions is adequate for valid dc spark tests, and that 1000 is necessary for ac tests because some number of sparks will occur at too low an instantaneous voltage, due to the ac waveform.  None of the SMEs, however, cite a specific source for this explanation.

4. ACRI2001 requires (under certain conditions) a more restrictive minimum interrupt current and minimum voltage rating for fuses, than do ANSI/ISA standards

ACRI2001 8.9.4                      ANSI/ISA 60079-11  7.3

ACRI2001 limits the current and voltage to which a fuse may be subjected (under a worst-case fault condition, i.e., two countable faults) to 2/3 of the maximum interrupting rating and 2/3 of the maximum allowable voltage specified for the fuse. This is effectively requiring that fuses have maximum current and voltage ratings that are 150% of the worst-case current and voltage to which they may be exposed.  In contrast, ANSI/ISA requires only that fuses have maximum current and voltage ratings that are equal to the worst-case current and voltage to which they may be exposed.  In other words, ACRI2001 supplies a 50% safety margin, whereas ANSI/ISA does not.  The fact that two simultaneous countable faults is a low probability fault condition may serve to mitigate any potential increased risk associated with the ANSI/ISA requirements.  Most SMEs queried noted that specifying a minimum value, either at full or 2/3 rating, is necessary for both interrupt current and maximum voltage ratings of fuses used in portable IS devices.  None of the SMEs offered an opinion on the adequacy of ANSI/ISA rating requirements as compared to ACRI2001.

5. ACRI2001 requires a more restrictive interpretation of ignition curves used to evaluate circuits than do ANSI/ISA standards (ignition curves are used in lieu of spark testing); specifically, ACRI2001 requires spark testing if circuit values fall between 90% and 100% of curve values

ACRI2001 6.2.1.1 through 6.2.1.3 (3 sections)                       ANSI/ISA 60079-11  10.1.1,  10.1.4.2 (a)

Under ACRI2001 and ANSI/ISA standards, circuits that meet certain criteria can be evaluated using ignition curves provided in the respective documents, in lieu of spark testing. In ACRI2001, the relevant circuit voltage or current values for these evaluations must not exceed 90% of the values specified by the ignition curves (for the circuit to pass).  Circuits yielding values between 90% and 100% on the curves must undergo spark testing, and circuits with values at or above 100% fail.  ANSI/ISA provides the same option allowing for use of ignition curves, but does not require testing for values falling between 90% and 100% on the curves, that is, circuits are accepted if relevant values are below 100%.  Circuits with values at or above 100% fail.  The potential increased risk with the ANSI/ISA criteria, however, may be mitigated to some degree by the fact that safety factors are applied to the voltage and current values in question, for one-fault and normal conditions, and ANSI/ISA safety factors exceed those applied by ACRI2001 for some types of circuits.

The ANSI/ISA SMEs queried generally feel that the requirement to run spark tests for circuits yielding between 90% and 100% (on the ignition curves) is unnecessary, pointing out that several factors in the use of ignition curves introduce a sufficient margin of safety without the 90% criteria. Specifically, 1) the curves represent low ignition probabilities based on extensive testing, 2) the evaluation criteria include safety factors applied to voltage and current levels for some cases, and 3) the use of ignition curves is limited to well-defined simple circuits.

6. For determining current levels to be used to evaluate circuit components, based on protective fuse ratings, ACRI2001 and ANSI/ISA standards use criteria that are similar, but cannot be compared directly

ACRI2001 8.9.3          ANSI/ISA 60079-11  7.3

ACRI2001 evaluates IS circuit components using a current level at which the protective fuse in question will open in 2 minutes or less. ANSI/ISA uses a current level of 1.7 x fuse nominal rating.  These criteria are difficult to compare without using specific fuse time-current characteristics, but they are similar in that both use short-time overcurrent levels for evaluation of fuse-protected components.  The SMEs queried provide no clear comparison of the two approaches, but two SMEs suggest that the difference may impact the temperature rating of components to some degree.

7. ACRI2001 spark test apparatus calibration procedures are somewhat more restrictive than those in ANSI/ISA standards; specifically, ACRI2001 allows fewer revolutions to achieve ignition, and specifies a resistive circuit calibration not called for by ANSI/ISA

ACRI2001 10.1.4.1 through 10.1.4.4 (4 sections)       ANSI/ISA 60079-11  10.1.3.1,  10.1.3.2,  B.1.3

ACRI2001 calls for 400 revolutions for spark test apparatus calibration, whereas ANSI/ISA calls for 440. ACRI2001 has distinct spark test apparatus calibration procedures for resistive and inductive circuits, but ANSI/ISA specifies calibration for inductive circuits only.  Based on SME input, it appears the two different criteria for the number of revolutions required come from a common source document that specified a range from 400 to 440, suggesting that the difference is an acceptable tolerance.  One ANSI/ISA SME noted that in practice, calibrations at his lab usually result in the desired ignition within the first 15 revolutions.  All ANSI/ISA SMEs queried feel that a separate resistive-circuit calibration is unnecessary, citing that calibration is a test of apparatus sensitivity at a known energy level, which should be independent of circuit configuration.  One ANSI/ISA SME feels that an inductive circuit yields more consistent results than a resistive circuit.

8. ACRI2001 creepage and clearance distances are more restrictive than those specified by ANSI/ISA 60079-11 Annex F

ACRI2001 7.1             ANSI/ISA 60079-11  Annex F

ACRI2001 Table 7.1 and ANSI/ISA 60079-11 Table 5 specify creepage and clearance distances. They are similar, with just several notable differences.  The most potentially significant difference is the ANSI/ISA allowance to use creepage and clearance distances less than those listed in Table 5, when other specific criteria are met, as detailed in ANSI/ISA 60079-11 Annex F.  The additional criteria allowing reduced distances include environmental controls (avoiding contamination), transient over-voltage limits, and enhanced insulation ratings (as further detailed in IEC 60664-1).  Most of the SMEs queried have little or no experience with Annex F.  One ANSI/ISA SME notes that his laboratory considers Annex F distances appropriate only for fixed installations, and therefore would not use them for portable devices (but this exclusion is not found in the standard).  Another of the ANSI/ISA SMEs notes that thus far, North American certifying bodies have generally been hesitant to employ Annex F provisions, preferring to rely on Table 5 in 60079-11.

9. ACRI2001 provisions to prevent potentially hazardous plug/receptacle interchangeability are more restrictive than corresponding ANSI/ISA standard requirements

ACRI2001 7.3.3          ANSI/ISA 60079-11  6.2.2

ACRI2001 requires that plugs and receptacles not be interchangeable with other plugs and receptacles if such interchange affects intrinsic safety. ANSI/ISA suggests that plugs and receptacles not be interchangeable, but as an alternative, that some form of obvious identification (such as color coding) be allowed as a means to avoid misconnection.  The use of visual identification alone to ensure proper connections may be of concern in a low-light, dusty environment such as underground mining.  When asked how frequently the need to apply these provisions occurs, SME responses varied from never to often, with one ANSI/ISA SME offering that, when it does occur, using visual identification alone to ensure proper connection would be unusual.

10. ACRI2001 has specific criteria for the use of optical isolators, but ANSI/ISA standards have no provisions specifically for optical isolators

ACRI2001 10.13.1 through 10.13.5 (5 sections)                     ANSI/ISA 60079-11  8.8.1,  8.8.2,  8.8.3

ACRI2001 has specific requirements associated with the use of optical isolators, but ANSI/ISA has no such specific provisions. Based on input from the queried SMEs, although optical isolators are sometimes encountered in portable IS devices, it is very unusual.  One ANSI/ISA SME states that his laboratory evaluates optical isolators in IS equipment using general ANSI/ISA 60079-11 requirements relating to minimum dielectric strengths, component ratings, and isolation of IS and non-IS circuits.  This SME also notes that the next release (6^th Edition) of ANSI/ISA 60079-11 will likely have requirements specifically for evaluating optical isolators.

The 6th Edition of ANSI/ISA 60079-11, in section 10.11, adds test requirements specifically for optical-isolators. The new ANSI/ISA test requirements are more extensive than those in ACRI2001, and so differences should not reduce the level of safety provided.  ANSI/ISA 60079-11 section numbers 8.8.1, 8.8.2, 8.8.3 have been renumbered as 8.9.1, 8.9.2, 8.9.3 in the 6^th Edition.

11. ACRI2001 has more explicit and restrictive requirements for the use of lithium batteries, than do ANSI/ISA standards

ACRI2001 9.3.14 through 9.3.14.4 (5 sections)                      ANSI/ISA 60079-11  7.4.1

ACRI2001 lists several explicit requirements for verifying the safe use of lithium-chemistry batteries in IS devices, most notably requiring passage of UL 1642 tests without resulting explosion or fire (UL, 2013), and prohibiting use of lithium-chemistry cells in user-replaceable applications. ANSI/ISA also acknowledges the need for additional measures to ensure safe use of lithium-chemistry batteries, but instead of employing specific requirements, states the use of such cells and batteries must be confirmed by their manufacturer as being safe for use in any particular intrinsically safe or associated apparatus under normal and fault conditions.  ANSI/ISA does not prohibit user-replaceable batteries, but does require warning markings (specifying the exact replacement cell) on the device for such cases.  The ANSI/ISA SMEs queried report that their laboratories always require UL 1642 compliance for cells and batteries used in IS devices, even if not specified in ANSI/ISA 60079-11.

4.2.2 Category II - Topics for which the ANSI/ISA deviations from ACRI2001 are not likely to have a material effect on the level of safety provided

For each of these topics, there is at least one element that is, or could be, more restrictive under ACRI2001, and although they should not be dismissed casually, the differences seem minimal or immaterial. Topics 12 through 28 in the list below (involving 35 ACRI2001 sections) are in this category.

12. ACRI2001 has fuse resistance testing requirements that are more explicit than those found in ANSI/ISA standards

ACRI2001 8.9.2          ANSI/ISA 60079-11  7.3,  8.4

ACRI2001 8.9.2 has requirements for characterizing fuse resistance that include current limiting resistor tests found in ACRI2001 10.3. Corresponding ANSI/ISA fuse requirements also refer to current limiting resistor tests, but the criteria for such tests are less specific.  Two ANSI/ISA SMEs queried do not feel there is a need to subject fuses to current limiting resistor tests.

ANSI/ISA 60079-11 section number 8.4 has been renumbered as 8.5 in the 6^th Edition.

13. ACRI2001 has specific, special spark testing procedures for evaluating circuits operating at over 10A, but ANSI/ISA standards have no such special procedures

ACRI2001 10.1.3.2.2              ANSI/ISA 60079-11  B.1.7

ACRI2001 criteria for spark test apparatus configuration require an increase in tungsten electrode size for tests between 5A and 10A. Corresponding ANSI/ISA criteria require a similar increase in tungsten electrode size for tests between 3A and 10A.  In addition, ACRI2001 specifies 24 AWG copper electrodes when testing at currents above 10A (the use of copper in this case reduces the chance of hot-wire ignitions).  ANSI/ISA has no specific criteria for testing above 10A, but does say special care in interpreting the results is necessary.  Most SMEs queried agree that the need to test a circuit at over 10A can readily arise when evaluating portable IS devices, particularly when considering fault conditions, but none cited the lack of ANSI/ISA guidance for such tests as a problem.

14. ACRI2001 does not allow the use of Phillips head fasteners under certain circumstances where ANSI/ISA standards would allow their use

ACRI2001 4.14, 9.3.10.2.2                ANSI/ISA 60079-11  7.4.7

ACRI2001 requires that, under certain circumstances, portable IS device battery housings be secured using special fasteners or an equivalent.  ACRI2001 does not consider flat-blade or Phillips head screws to be special fasteners. Corresponding ANSI/ISA 60079-11 requirements are somewhat ambiguous on this issue, due to a national difference in Section 7.4.7 by which the phrase special fastener (from the original IEC language) is removed and replaced with a requirement that removal of battery housings must only be possible with the aid of a tool.   From a practical standpoint, 2 of 3 ANSI/ISA SMEs queried state that Phillips head screws are allowed in ANSI/ISA device certifications at their laboratories, in cases where the aid of a tool is required.  In general, it appears an ANSI/ISA or IEC certified device may have Phillips head screws in an application where MSHA would not approve them.

15. ACRI2001 calls for selection of wire and trace sizes based on ampacity test criteria, whereas ANSI/ISA standards use explicit detailed specifications for size and configuration of wires and traces

ACRI2001 10.16         ANSI/ISA 60079-11  8.7

ACRI2001 requires that wires and traces be tested to ensure they are capable of carrying, for 1 hour, 1.5 times the maximum continuous current to which they may be subjected. ANSI/ISA addresses the issues of ampacity, and to some degree mechanical integrity, by specifying wire and trace sizes and configurations in detail.  ANSI/ISA also allows, as an option for some applications, testing equivalent to the ACRI2001 test criteria above.

16. ACRI2001 provisions to prevent potentially hazardous interchangeability of circuit boards and components, are more restrictive than corresponding ANSI/ISA standard requirements

ACRI2001 9.2             ANSI/ISA 60079-11  7.2

ACRI2001 requires that plug-in boards and components not be interchangeable with non-identical boards or components if the interchange will affect intrinsic safety. ANSI/ISA suggests that plug-in boards and components not be interchangeable unless the interchange does not affect intrinsic safety, or the connectors are identified so that the misconnection is obvious.  This issue does not seem to present as much risk as interchangeability of external plugs and receptacles (item #9, previously covered), since the type of work described here seems more likely to be performed by a trained technician in a non-hazardous location, rather than by an end-user during normal field operation.  Two of the SMEs queried, however, feel that these provisions (ACRI2001 9.2 and ANSI/ISA 7.2) refer not only to work to be done by trained technicians, but also to connections that could be made by the end-user in the field.

17. ACRI2001 and ANSI/ISA standards have similar provisions addressing small component thermal ignition, but some differences exist

ACRI2001 9.5.3          ANSI/ISA 60079-11  Table 2a

ACRI2001 10.6 through 10.6.5 (6 sections)    ANSI/ISA 60079-0  26.5.3,  ANSI/ISA 60079-11  5.6.2

The criteria addressing small component thermal ignition within ACRI2001 and ANSI/ISA standards are similar, but the differences are somewhat complex, making direct comparison inconclusive. ACRI2001 and ANSI/ISA standards, however, both seem to cover the same critical aspects of small component temperature limits and testing.

18. ACRI2001 has guidelines for testing oscillators, but ANSI/ISA standards do not include test procedures specifically for oscillators

ACRI2001 10.1.7.2     ANSI/ISA 60079-11  7.1,  10.1.4.1

ACRI2001 specifies that oscillators must be tested considering the worst-case tolerance values and faults of associated components. ANSI/ISA has no such specific requirement, but oscillators would be similarly covered by the general provisions within the ANSI/ISA standards addressing component ratings and tolerances.

19. ACRI2001 and ANSI/ISA standards have similar requirements for testing of piezo-electric devices, but some differences exist

ACRI2001 9.4, 10.15.1 through 10.15.3 (3 sections) ANSI/ISA 60079-0  26.4.2,  ANSI/ISA 60079-11  7.7, 10.7 

ACRI2001 and ANSI/ISA standards both require testing IS equipment containing piezo-electric devices to ensure that such devices do not output over 1500 micro-Joules as the result of mechanical impact. ACRI2001 10.15, when applied using MSHA ASTP 2230, calls for 2 tests each on 3 samples, using 20 J impact energy.  ANSI/ISA calls for 2 tests each on 2 samples, and specifies 1 kg dropped from 2 m, which is 19.6 J impact energy.

20. ACRI2001 requirements for conformal coatings are based on thickness or dielectric strength, but ANSI/ISA standards do not use these criteria to specify acceptable conformal coatings

ACRI2001 7.1.5.1, 7.1.5.2     ANSI/ISA 60079-11  6.3.8,  6.3.9

ACRI2001 requires a minimum thickness or minimum dielectric strength for conformal coatings. ANSI/ISA does not have explicit thickness or dielectric strength requirements, but requires the coating to provide an effective lasting unbroken seal.  ANSI/ISA also specifies the number of coats required based on application method, as well as the comparative tracking index (CTI) required where conductors emerge from beneath the coating.

21. ACRI2001 requires specific testing of encapsulant that has been overheated, but ANSI/ISA does not specify how overheated encapsulant should be evaluated

ACRI2001 7.2.1.3       ANSI/ISA 60079-11  6.6

If an encapsulated component exceeds the temperature rating of the encapsulant, ACRI2001 requires specific tests to verify retention of encapsulant mechanical strength. In the same situation, ANSI/ISA requires that such temperatures do not cause any damage to the casting compound that would adversely affect the type of protection (i.e., intrinsic safety), but does not specify what criteria to use.  The SMEs queried report that this situation occurs infrequently.  ANSI/ISA SMEs further state that in this situation, the overheated encapsulant would be subjected to a thorough visual examination.

22. ACRI2001 and ANSI/ISA standards specify normal operation temperature range differently

ACRI2001 5.2.4          ANSI/ISA 60079-0  Scope

For IS evaluations, ACRI2001 specifies 40^oC as the maximum ambient temperature assumed for normal conditions, but does not specify a minimum temperature.  ANSI/ISA assumes a normal ambient temperature range of -20 ^oC to 40 ^oC, but allows different ranges if necessary.  The ANSI/ISA SMEs queried state that IS evaluation criteria are modified as needed when a different temperature range is used.

23. ACRI2001 requirements for testing the strength of non-metallic partitions are more restrictive than those in ANSI/ISA standards

ACRI2001 7.3.2.4       ANSI/ISA 60079-11  6.2.1

ACRI2001 requires mechanical testing of all nonmetallic partitions to ensure adequate strength. ANSI/ISA requires similar testing, but only for nonmetallic partitions less than 0.9 mm thick.

24. ACRI2001 requirements for rigidity testing of encapsulant are in part, more restrictive than those in ANSI/ISA standards

ACRI2001 7.2.1.2, 7.2.2.2, 7.2.3.3     ANSI/ISA 60079-11  6.6, 10.6.1

Where encapsulation is used to separate conductors and components, to reduce the risk of ignition of a potentially flammable atmosphere, or to reduce surface temperature, ACRI2001 always requires testing of the encapsulated assembly to ensure adequate rigidity. ANSI/ISA requires such testing only when the encapsulant has an exposed surface (not in a protective enclosure).  ACRI2001 specifies only a static load test for most applications, but ANSI/ISA specifies both static and impact tests for those cases where testing is required.

25. ACRI2001 criteria for certain wires, connections, and traces cites the use of an IP55 protection rating as one optional technique, but ANSI/ISA standards include no equivalent criteria

ACRI2001 8.11                       ANSI/ISA 60079-11  8.7

ACRI2001 8.11 inclusive specifies requirements for the size and installation of wires, connections, and traces, such that it can be assumed that these conductors will not fail as an open circuit (for the purposes of IS evaluations). One option for environmental protection under these ACRI2001 requirements is the use of an IP55 rating for dust and water intrusion (as per IEC 60529).  For an IP rating, the first digit denotes protection from dust, with a 5 suitable for coal dust exposure in a mine.  The last digit denotes water exclusion, with 4 adequate for splashing, and 5 suitable for a directed jet of water.  ANSI/ISA 60079-11 8.7 has corresponding requirements closely matching those of ACRI2001. The most protective dust and water intrusion rating cited in ANSI/ISA 60079-11 is IP54 in Section 6.1

26. ACRI2001 requirements with respect to dust-tight enclosures are more specific than those in ANSI/ISA standards

ACRI2001 7.5.1 through 7.5.5 (5 sections)    ANSI/ISA 60079-11  6.1

ACRI2001 explicitly lists dust-tight enclosure requirements, criteria, and acceptable examples. ANSI/ISA specifies only that the degree of protection required [from an enclosure] will vary according to the intended use, but does cite a protection rating of IP54 as an example of adequate protection for Group I devices, in ANSI/ISA 60079-11 Section 6.1.  ACRI2001 Section 7.5.3 states that an enclosure IEC rated at IP5X is acceptable as dust-tight.  All ANSI/ISA SMEs queried say that in practice, an IP54 rating would be considered the minimum acceptable protection rating for a Group I (mining) device.

27. ACRI2001 has clear criteria with respect to the battery voltage to be used for circuit evaluations, but corresponding ANSI/ISA standard requirements are ambiguous

ACRI2001 8.4.2 (note)                        ANSI/ISA 60079-11  7.1,  8.4

ACRI2001 9.3.6                      ANSI/ISA 60079-11  7.4.3

ACRI2001 uses peak open circuit battery voltage when determining the maximum fault voltage for a battery powered circuit, for sizing current limiting resistors, and for spark tests. ANSI/ISA is not clear or explicit on what battery voltage should be used for such cases (nominal, or peak open circuit).  All ANSI/ISA SMEs queried, however, state that maximum (peak) open circuit voltage for a battery would always be used.

28. ACRI2001 and ANSI/ISA standards have different provisions for assessing the adequacy of encapsulant in contact with insulation

ACRI2001 7.2.2.1 (note)         ANSI/ISA 60079-11  6.3.4

When encapsulant is in direct contact with insulation, such as at the wall of a non-conductive enclosure, ACRI2001 adds the insulation thickness as if it is additional encapsulant, although insulation and encapsulant have different thickness requirements in ACRI2001 Table 7.1. ANSI/ISA considers each individually, based on the thicknesses required in ANSI/ISA 60079-11 Table 5.  For nominal circuit voltages over 10 V, the ACRI2001 criteria requires a greater combined thickness of encapsulant and insulation, than does the ANSI/ISA criteria, for a given voltage.

4.2.3 Input from MSHA on findings for the comparison of IS standards

As explained previously (section 4.1) the subject comparison of ACRI2001 and ANSI/ISA IS standards was structured to be an unbiased review of IS construction and testing criteria, and the findings reflect input consolidated from all the experts involved, including NIOSH engineers and consultants, ANSI/ISA experts, and an expert MSHA representative. In addition, the MSHA Approval and Certification Center (A&CC) has numerous staff members that have extensive experience dealing with ACRI2001 as well as approval inquiries from manufacturers with existing IEC-certified products.  To utilize this expertise, NIOSH requested that MSHA A&CC conduct an informal review of the foregoing comparison findings.  A&CC Electrical Safety Division (ESD) personnel, including representatives from the Intrinsic Safety Group, responded with comments reflecting their collective equipment approval experience and engineering judgment with respect to IS issues.  This input was supplied as a courtesy by the ESD staff, and does not represent an official MSHA response or position, but is included here because it provides an informative supplement to the independent NIOSH study results.

The ESD engineers generally agree that the 28 topics identified by the NIOSH study represent differences for which ACRI2001 criteria, to some degree, appear more restrictive than ANSI/ISA provisions. They did, however, identify specific topics among those 28, that: 1) they would characterize and prioritize differently from the NIOSH study, 2) they have found to be problematic in their past evaluations of equipment originally designed to meet IEC IS standards, and/or 3) they feel require further investigation.  They also suggested two topics not included among the 28.  The issues they identified are listed below, with the nature of their exception noted for each.

1. Maximum temperature limits for small/low-power electronic components are higher under ANSI/ISA 60079-11 than under ACRI2001 (Topic #17) – This allowance of higher temperatures is a more significant issue than suggested in NIOSH results
2. When specifying the current level at which to evaluate circuit components, ANSI/ISA 60079-11 uses 1.7 x the protective fuse nominal rating, while ACRI2001 uses a current level that will open the fuse in 2 minutes or less (Topic #6) – The inability to directly compare fuses sized using these two approaches is a common problem when evaluating IEC-certified equipment against ACRI2001 criteria
3. For encapsulant used to isolate electronic components from hazardous atmospheres, testing requirements employed by MSHA are more extensive than those under ANSI/ISA IS 60079-11 (Topics #21, 24, and 28) – For certain uses of encapsulant, MSHA uses criteria found in ACRI2010 (MSHA, 2009) in addition to ACRI2001, and as a result, this issue is more significant than suggested in the NIOSH results
4. The use of alternate test gas mixtures to introduce a safety factor in spark testing is prohibited by ACRI2001, but allowed by ANSI/ISA 60079-11 (Topic #2) – Past MSHA ESD laboratory test results suggest that the prohibition of alternate test gases may be warranted under certain circumstances
5. Special spark testing procedures for evaluating circuits operating at over 24 V and/or 60 Hz are unique to ACRI2001 (Topic #1) – Past MSHA ESD laboratory test results suggest that such special testing may be warranted under certain circumstances
6. When using published curves for evaluation of circuits, ACRI2001 uses a more restrictive procedure than ANSI/ISA 60079-11, requiring testing when results are above 90% of the curve values (Topic #5) – This effective “safety margin” in ACRI2001 is not arbitrary, but actually originated in past UL IS standards from which ACRI2001 evolved; therefore, further investigation of this issue may be warranted
7. The use of lithium-chemistry batteries is regulated by ACRI2001 requirements that are more explicit and restrictive than those found in ANSI/ISA 60079-11 (Topic #11) – The difference of most concern is the absence of an ANSI/ISA requirement that batteries pass UL 1642 tests without “flashing” or catching fire
8. ANSI/ISA 60079-11 Annex F allows creepage and clearance distances less than any specified in ACRI2001 (Topic #8) – Further investigation of the technical basis and development of Annex F criteria, may be warranted
9. Spark test apparatus calibration procedures are more restrictive in ACRI2001 than in ANSI/ISA 60079-11 (Topic #7) – The difference of most concern is the absence of an ANSI/ISA requirement for a specific resistive-circuit calibration
10. New topic: Ignition curves provided in ACRI2001 (11.0) and ANSI/ISA 60079-11 (Annex A) have deviations (when overlaid) that warrant further investigation – This issue is not included in the NIOSH list of 28 topics
11. New topic: The equipment drop tests in ACRI2001 (10.10) and ANSI/ISA 60079-0 (26.4.3) are sufficiently different to warrant further investigation – This issue is not included in the NIOSH list of 28 topics
12. Spark testing criteria are more restrictive in ACRI2001 than in ANSI/ISA 60079-11, with respect to the number of test apparatus revolutions required for dc circuits (Topic #3) – Further consideration of the technical basis for the ACRI2001 criteria may be warranted, but this difference may ultimately be less significant than suggested in the NIOSH results
13. The minimum required current interrupt rating and voltage rating for fuses, under some circumstances, is 50% higher under ACRI2001 than under ANSI/ISA 60079-11 (Topic #6) – This issue warrants further consideration, but may ultimately be less significant than suggested in the NIOSH results
14. Several topics in the NIOSH list may ultimately be of minimal significance because they are rarely relevant to portable IS devices—specifically, the use of optical isolators (Topic #10), interchangeability of circuit boards (Topic #16), and non-metallic partition strength testing (Topic #23)

[1]MSHA does not approve or endorse private laboratories capable of testing for MSHA equipment approvals, but does maintain a list of laboratories that have done MSHA approval testing in the past.

[2] Many ACRI sections have multiple provisions within them, and in a few cases a section will be cited in more than one category in this comparison, so the number of sections listed for each category will sum to greater than 362.

5. Comparison of ACRI2001 and IEC IS standards safety records

The foregoing comparison of MSHA ACRI2001 and ANSI/ISA 60079-0 and 60079-11 was essential for identifying specific differences that, if considered individually, may appear to influence the level of safety provided by either system. For example, ANSI/ISA requirements result in a safety factor of 2.25 for power in some IS circuit evaluations under normal and single-fault conditions for which ACRI2001 would apply a safety factor of 1.5, making ANSI/ISA criteria more restrictive.  In contrast, ACRI2001 requires that for certain circumstances, an IS device must have plug/receptacle combinations that render it physically impossible to make an incorrect field connection, while ANSI/ISA criteria would allow labeling or other markings alone to prevent such an error, making ACRI2001 more restrictive.  It can be argued, however, that such a focused evaluation overlooks at least two important points.  First, that both sets of IS criteria evolved as systems that were intended to be applied in their entirety, and a point-by-point comparison fails to consider the overall effect of many individual requirements working in concert.  Second, that while a particular provision in one system may be more restrictive than the corresponding requirement from the other, both may be beyond the level needed to materially affect overall safety, and so citing one as safer may be somewhat academic.  In fact, unnecessarily restrictive requirements could actually be counterproductive, by impeding the introduction of technology with the potential to improve mine safety.

5.1 Material and methods (Comparison of ACRI2001 and IEC IS standards safety records)

Given the limitations of a comparison of specific IS criteria, this study complemented that approach by conducting a comparison of the safety histories of ACRI2001 and IEC IS standards (with IEC standards being the basis of ANSI/ISA IS standards). This broader approach first focused on determining if either system has had documented failures (i.e., documented cases of IS approved/certified devices igniting methane or coal dust in underground coal mines), and then verifying the significance of these failure histories by estimating cumulative coal mine exposure times for portable IS devices conforming to each system.  The U.S. coal industry was used to assess ACRI2001, and Australia and South Africa were chosen to represent foreign countries with large, modern underground coal industries that have used IEC-based standards for portable IS equipment for at least several years.[1]

5.2 Results and discussion (Comparison of ACRI2001 and IEC IS standards safety records)

In the U.S., the use of ACRI2001 has provided excellent safety, with no known cases of an MSHA-approved IS device causing a gas or dust ignition in a U.S. underground mine since it was formalized and adopted in 1995.

Australia used its own national standards—the AS 2380 series—to approve portable IS equipment for use in underground coal mines prior to 2000. In 2000, AS/NZS 60079-11, identical to IEC 60079-11, was adopted for mining use and replaced the AS 2380 series.  James Birch, formerly a manager at the Safety in Mines Testing and Research Station (SIMTARS) in Queensland, Australia, reports that there has been, to his knowledge, no case of a certified IS device igniting gas or coal dust in an Australian coal mine since the AS/NZS (IEC) standard was adopted.  In addition, at a recent Australian IS standards committee meeting, the members reported that they also have no knowledge of an ignition caused by a certified IS device under the AS/NZS (IEC) standard (Birch, 2012).

South Africa also used its own national standard for approving portable IS equipment prior to the early 1990s, and in addition, accepted certifications from a number of foreign approval organizations. Subsequently, the South African National Standard, SANS 60079-11, identical to IEC 60079-11, was phased in over time, until it became the national standard for approving electronic equipment for use in underground coal mines in 2005.  Some South African standards are still in use, but none conflict with IEC 60079-11 requirements.  All electronic equipment imported into South Africa for use in underground coal mines is required to comply with SANS 60079-11, and must be issued a certificate by a South African testing laboratory, although this usually requires only a paperwork review to ensure that the IEC certification process is complete.  Since 2005, MSHA-approved equipment is no longer accepted without a full approval investigation using SANS 60079-11 requirements.  Mr. Paul Meanwell, former Chair of the IEC Secretariat in South Africa, reports that he knows of no case of a certified IS device igniting gas or coal dust in a mine in that country since the adoption of the SANS (IEC) standard, and also noted that the South African Flameproof Association (SAFA) committee knows of no such cases (Meanwell, 2012).

Before drawing conclusions based on the absence of IS-device-related ignitions in Australia and South Africa, some measure must be made of the exposure of IS devices to potentially explosive atmospheres in mines in these countries, as well as the U.S. To accomplish this, annual underground coal mine exposure time for portable IS devices was estimated using the number of underground miners, average hours worked for each, and the number of devices in use by each miner.  U.S. underground coal mine exposure time for MSHA-approved portable IS devices is estimated to have been 270 x 10⁶ device-hours in 2010.  The estimate for IEC-certified device exposure in Australia for 2011 is 20 x 10⁶ device-hours, and for South Africa, the estimate is 13 x 10⁶ device-hours for 2010.  The exposure estimate for MSHA-approved devices is several times that for IEC-certified devices due not only to the larger coal industry in the U.S. when compared to Australia and South Africa, but the much more extensive use of portable electronic devices, particularly communications and tracking devices.  It should also be noted that this comparison of IS-device exposure does not account for differences in other factors such as the overall approach to explosion protection, mining methods and equipment, and mining conditions (e.g., methane liberation).

To summarize this comparison, Australia and South Africa, among the top coal producing nations globally, have used IEC IS standards for underground coal mine equipment for 12 years and 7 years, respectively, without an IS device causing a gas or dust ignition. Using recent data, together they account for an estimated 33 million hours of underground exposure of IEC-certified IS devices annually, in comparison to an annual exposure of 270 million device-hours for MSHA-approved devices in the U.S. Although Australia’s and South Africa’s use of IEC IS certification have shorter histories and less device exposure than the use of MSHA IS approvals in the U.S., they nonetheless represent significant applications of IEC standards in the mining environment, and their performance histories have exhibited an overall level of safety equivalent to that provided by ACRI2001. This suggests that both systems reliably prevent coal mine gas or dust ignitions due to IS equipment failure.

[1] The USA, Australia, and South Africa are among the top 5 hard coal producing countries based on 2010 data (#2, #4, and #5, respectively), making up approximately 25% of total world production (internationally, hard coal is generally equivalent to bituminous coal in the U.S.). China (#1) accounts for 51% of world production, and Russia (#6) is comparable to South Africa at 4%, but accurate, reliable, detailed data about the coal industries in China and Russia is not practically accessible.  India (#3) also has a large coal industry, representing more than 8% of world production, but has only recently started to adopt IEC standards. Data are from the World Coal Association.

Summary

This report detailed findings of a NIOSH study examining potential benefits and safety issues associated with the use of IEC IS standards for certification of portable electronic devices for use in U.S. mines. The research reviewed IS portable equipment for underground mining to identify technologies not currently available to U.S. mines, conducted a detailed comparison of ACRI2001 and corresponding IEC-based IS standards, and examined the safety histories of both ACRI2001 and IEC IS standards as applied in underground mining.

The review of IS portable equipment compared the quantity and variety of devices currently (2012) available under MSHA and the IEC. This effort identified 59 IEC-certified portable IS devices and one ATEX-certified device that meet IS criteria most nearly equivalent to those for MSHA approval, but are not also MSHA-approved.  When these 60 products were compared to the 207 currently (2012) available MSHA-approved portable IS devices, three of the IEC/ATEX-certified devices were found to offer functions and capabilities not available among the MSHA-approved equipment, specifically, a digital camera, a personal digital assistant (PDA), and a laser bar code scanner.

The detailed study of IS requirements and criteria compared the MSHA IS criteria document ACRI2001 to the standards ANSI/ISA 60079-0 and 60079-11 (5^th Editions, 2009), which are the U.S.-adopted versions of IEC standards relevant to intrinsic safety, IEC 60079-0 and 60079-11.  The ANSI/ISA standards in question have original IEC mining-related criteria removed as part of the revisions made to accommodate use in the U.S., but those criteria were reinserted and treated as if still in force for this comparison.  Referencing the 362 individual sections of ACRI2001, work focused primarily on the 66 sections having provisions that appear to be more restrictive than their ANSI/ISA counterparts, or having differences from ANSI/ISA criteria that do not allow an effective comparison.  These 66 sections were organized under 28 distinct technical topics for further analysis, each of which was ultimately assigned to one of two categories suggesting their potential impact on IS equipment safety.  The categories are (I) Topics for which the ANSI/ISA deviations from ACRI2001 are substantive, but it is not clear if they would have a material effect on the level of safety provided (11 of 28), and (II) Topics for which the ANSI/ISA deviations from ACRI2001 are not likely to have a material effect on the level of safety provided (17 of 28).

In addition to the detailed IS criteria comparison, a comparison of ACRI2001 and IEC IS standards safety records in mining was conducted. In the U.S., ACRI2001 has maintained an excellent safety record since it was first formalized and adopted in 1995, with no known gas or dust ignitions from approved IS devices. In comparison, the large coal producers Australia and South Africa have used IEC IS standards for 12 and 7 years, respectively, and report no known gas or dust ignitions from IEC-certified IS equipment. U.S. underground coal mine exposure time for MSHA-approved portable IS devices is estimated to have been 270 million device-hours in 2010, while Australia and South Africa have a combined 33 million IS device-hours exposure underground each year, based on recent data.

Disclaimer

The findings and conclusions in this paper are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health (NIOSH).

References

30 CFR, 2016a. Title 30 - Code of Federal Regulations.  30 CFR 75.2, 75.500, 75.507, and 75.1002.  https://arlweb.msha.gov/regs/30cfr/ (accessed 7-26-16).

30 CFR, 2016b. Title 30 - Code of Federal Regulations.  30 CFR Part 6.   https://arlweb.msha.gov/Part6SingleSource/Part6SingleSource.asp (accessed 7-26-16).

30 CFR, 2016c. Title 30 - Code of Federal Regulations.  30 CFR 75.313, 75.320, 23.6, and 75.1103-7.  https://arlweb.msha.gov/regs/30cfr/ (accessed 7-26-16).

ANSI/ISA, 2009a. ANSI/ISA 60079-0 (12.00.01)-2009.  Explosive atmospheres – Part 0: Equipment – General Requirements, 5^th Edition.  ANSI/ISA, Research Triangle Park, NC, 27709.

ANSI/ISA, 2009b. ANSI/ISA 60079-11 (12.02.01)-2009.  Explosive atmospheres – Part 11: Equipment protection by intrinsic safety “i”, 5^th Edition.  ANSI/ISA, Research Triangle Park, NC, 27709.

ANSI/ISA, 2012a. ANSI/ISA 60079-0 (12.00.01)-2012.  Explosive atmospheres – Part 0: Equipment - General Requirements, 6^th Edition.  ANSI/ISA, Research Triangle Park, NC, 27709.

ANSI/ISA, 2012b. ANSI/ISA 60079-11 (12.02.01)-2012.  Explosive atmospheres – Part 11: Equipment protection by intrinsic safety “i”,6^th Edition.  ANSI/ISA, Research Triangle Park, NC, 27709.

ANSI/UL, 2009a. ANSI/UL 60079-0 2009-10.  Explosive atmospheres – Part 0: Equipment – General Requirements, 5^th Edition.  https://www.shopulstandards.com/Catalog.aspx (accessed 7-26-16).

ANSI/UL, 2009b. ANSI/UL 60079-11 2009-09.  Explosive atmospheres – Part 11: Equipment protection by intrinsic safety “i”, 5^th Edition.  https://www.shopulstandards.com/Catalog.aspx (accessed 7-26-16).

Birch, 2012. Mr. James Birch, Manager (retired), Engineering Testing and Certification Centre, SIMTARS.  Mines and Energy, Department of Employment, Economic Development and Innovation, 2 Smith Street,  Redbank Qld 4301, PO Box 467  Goodna Qld 4300, Australia.  Personal communications, 2012.

IEC, 2011a. IEC 60079-0 Edition 6.0, 2011-06.  Explosive atmospheres – Part 0: Equipment – General Requirements.  https://webstore.iec.ch/preview/info_iec60079-0%7Bed6.0%7Db.pdf (accessed 7-26-16).

IEC, 2011b. IEC 60079-11 Edition 6.0, 2011-06.  Explosive atmospheres – Part 11: Equipment protection by intrinsic safety “i”.  https://webstore.iec.ch/preview/info_iec60079-11%7Bed6.0%7Db.pdf (accessed 7-26-16).

IECEx, 2016. IEC System for Certification to Standards relating to Equipment for use in Explosive Atmospheres.   https://www.iecex.com/ (accessed 7-26-16).

Magison, 1998. Magison, E., 1998.  Electrical Instruments in Hazardous Locations, 4^th Edition.  International Society for Automation (ISA), Research Triangle Park, NC, 27709, 1998.  Pp. 103-105.

Meanwell, 2012. Mr. Paul Meanwell, former Chairperson, IEC Secretariat, Standards South Africa.  pmeanwel@joy.co.za. Personal communications, 2012.

MSHA, 2008. Mine Safety and Health Administration, ACRI2001. https://arlweb.msha.gov/techsupp/acc/application/acri2001.pdf (accessed 7-26-16).

MSHA, 2009. Mine Safety and Health Administration, ACRI2010. https://arlweb.msha.gov/TECHSUPP/acc/application/acri2010.pdf (accessed 7-26-16).

MSHA, 2016a. Mine Safety and Health Administration, Approval and Certification Center. https://www.msha.gov/about/program-areas/technical-support/approval-and-certification-center (accessed 7-26-16).

MSHA, 2016b. Mine Safety and Health Administration, Approval and Certification Center, List of Approved Products. https://arlweb.msha.gov/TECHSUPP/ACC/lists/lists.htm (accessed 7-26-16).

Queensland, 2012. Office of the Queensland Parliamentary Council, 2012. Queensland Coal Mining Safety and Health Regulation 2001.  Reprint No. 31, February 17, 2012.

Snively, 2016. Snively, Inc., 2016. MSHA Permissible i.roc Ci70-EX.  http://www.snivelyinc.com/i.roc-Ci70-EX/MSHA-iroc.Ci70-EX-NUMERIC/ (accessed 7-26-16).

UL, 2013. Standard for Safety for Lithium Batteries, UL 1642, 2013. Underwriters Laboratories, Inc., Northbrook, IL. Ed. 5, July 2013.

Author Information

Gerald Homce — Lead Electrical Engineer (corresponding author)
Contact him at: (412) 386-5097 or  GHomce@cdc.gov

Joseph Waynert — Team Leader, Electrical Safety and Communications Team (retired)

Michael Yenchek — Senior Electrical Engineer (retired)

R.J. Matetic — Director, Pittsburgh Mining Research Division
Contact him at: (412) 386-6601 or  RMatetic@cdc.gov

All authors are current or retired employees of:

National Institute for Occupational Safety and Health
Pittsburgh Mining Research Division
626 Cochrans Mill Road
Pittsburgh, PA 15236

Supplemental Information

Currently commercially available permissible portable electrical/electronic devices from Parts 18, 19, 20, 22, and 23 of MSHA’s list of approved products (current as of July, 2012)

This information supplements the subsection: 3.1.1 Identifying currently available MSHA-approved portable IS devices.

Part 18 – Instruments (available)

Approval	Company	Description/Model
2G-4081	A.T.S. Electro-Lube International	Models M125, J475 & B250 Permissible Lubricators
2G-3925	Ansul Fire Protection Inc	Checkfire MP Fire Detection/Suppression System 7.2V
2G-4107	Ansul Inc.	Checkfire MP-N Vehicle Fire Detection/Supression System
18-A080001	App-Tek International	Model Odadisk
18-A080010	Austdac Pty	Type MFLA3 Roadside Flasher
18-A080018	Austdac Pty	Type MFLA5 Emergency Strobe
2G-4061	Bach Simpson Corp	Model TS393 Digital
18-A060028	Biomarine-Nitron	Model RMS Pressure & Temperature Monitoring Device
2G-3949	Bramall Laser Systems	Model MK7 Alignment Laser
18-A080003	BWI Eagle	Model 36 1200-BAT
18-A080003	BWI Eagle	Model 38-1300RF Transmitter
2G-4127	Cattron Theimeg	Model T01MS Radio Remote Control
18-A090009	Cavotec	Radio Remote Control
2G-4106	Centurion Safety Products	Model E140ISEWUSA Max Miner Pwrd Respirator Miners Helmet Respirator System
18-A060027	Cirrus Research	Model CR:110AIS Dosebadge Noise Dosimeter
2G-4168	Conspec Controls	Model 911118 Keypad Encoder
2G-4066	Conspec Controls	Model P2674 Tracking Transmitter
18-A070003	Detector Elect. Corp	PIR9400 Combustible Gas Detector
18-A070003	Detector Elect. Corp	U9500 Infinity Gas Transmitter System (16-32V)
18-A080008	Draeger Safety	Model Sentinel BG4 Electronic Signals & Warning Device
2G-4064	Draeger Sicherheitstechnik	Model CMS Gas Analyzer
2G-4065	Draeger Sicherheitstechnik	Model Polytron 2 XP Remote Control
2G-3479	E.I.T. Corporation	Model "D" Disposable Blasting Galvanometer, 1 VDC, Silver Chloride Battery-Powered
18-A070009	E.S.G. Canada	Paladin Data Acquisition System
2G-3497	Ectron Corporation	Model No. 418, 12 VDC, Differential DC Amplifier and Signal Conditioner
2G-4072	Eickoff	Radio Remote Control
18-A040006	Eickoff	Radio Remote Control
2G-4082	Engineering Seismology Group Canada	Hyperion Seismic Monitoring
18-A030001	Falconer Electronics, Inc.	Model J100 LED Flashing Signal Lamp
18-A100015	Fluke Corporation	Model 27II, 28II digital Multimeters
18-A110014	Fluke Corporation	Model TIC 300 PRO VOLTAGE Detector
18-A050004	Forced Potato	Type ML Remote Control Console
2G-4084	Forced Potato	Type U-OHR Remote Control
2G-4137	Forced Potato	Radio Remote Control
2G-3044	GenRad Inc	Model No. 1982, 3.8 VDC, Battery-Powered Precision Sound Level Meter & Analyzer
2G-3551	GenRad Inc	Model No. 1986, Omnical Sound Level Calibrator
18-A100007	Grace Industries	Lite Tracker 2000M Series Personal Safety Light
18-A080004	Grace Industries	Model Mine Rescue Alarm (M-R-A) Man-Down Alarm
2G-3845	Gullick Dobson (Trans to Joy)	Machine Position
18-A050012	Industrial Scientific	Model Gasbadge Plus Personal Single Gas Monitor
2G-4004	Johnson Industries	Model Pathfinder Slimm Jimm Alignment Laser
18-A040008	Joy Mining Machinery	Model 5000019506 M-Log System
18-A070006	Joy Mining Machinery	Model XR1 Handheld Transceiver
2G-4045	Kasco Via Romania (Italy)	Model K80E T8 powered Air Purifying Respirator
2G-4121	Larson Davis	Model 703 to 706RC Permissible Noise Dosimeters
2G-4022	Laser Tools	Model L350 Alignment Laser
18-A050006	Laser Tools	Model L80 Powerline Sheave Alignment Laser
18-A070005	Laser Tools	Models 10801 & 1080 LED Permissible Strobe Light
18-A070010	Laser Tools	Models GL340, GL222, etc. Green Beam Laser Tools
2G-4089	Matric Limited	Model 500-669 Bi-Directional Hall Effect Station
2G-4096	Matric Limited	Model TX3, Radio Transmitter
18-A080014	Matrix Design Group	P/N M3-1000 Matrix Miner Monitor Proximity Transmitter
2G-3730	Mefcor Inc	Model WL88A Warning Light
2G-3850	MST (Microsensor Tech)	Model MSTOX 8600 D Personal Portable Gas Monitor
18-A080013	Nautilus International Control & Eng	Model Flat-top BP-888 Battery Case Proximity Detection Circuit
18-A070014	Neilsen-Kellerman	Model Kestrel PMA2 Pocket Wind Meter
18-A100005	NL Technologies	Fixed Access Node
18-A100002	NL Technologies	Permissible Compact Access Node System
2G-3931	Quest Technologies	Model QC-10 Acoustic Calibrator
18-A040003	Quest Technologies	Models Quest NoisePro & Metrosonics DB-4000EZ Noise Dosimeter
2G-3655	REL-TEK CORP	Fireboss 1001, Handheld CO Detector
2G-4108	Ridgeline	Pro-Ears Electronic Hearing Protectors (DIM-1)
2G-4109	Rock Mechanics	Model RDL-4 Acoustic Energy Meter
2G-4073	Safety Devices	Model SD-103 Blasting Galvanometer
2G-3690	Safety Devices	Permissible Blasters Digital (IA514) Ohmmeter Model No.105
18-A110002-0	Sensidyne, LP	CDEM-1000 Coal Dust Explosibility Meter
2G-3585	Sensidyne, LP	LSF 113D/LSF 113DC, Low Flow Sampler
2G-2790	SKC INC	Models 222-3 and 222-4, 2.5 VDC, Battery-Powered Personal Sampling
2G-4036	SKC Inc.	Model 224-44XRM, 2240PCXR8M
2G-3947	SKF Condition Monitoring	Model CMVA30/M Portable Data Collector
18-A070021	Sperian Protection Instrumentation	Models Biosystems Toxi Pro etc. Portable Single Gas Detectors
18-A050003	Stolar Horizon	RIM IV Radio Imaging Downhole System
2G-4057	Structured Mining Systems	Model BDT-100 Infrared Transmitter
18-A050010	Structured Mining Systems	Model TX-94X Remote Control Transmitter
18-A040005	Structured Mining Systems	Models TX-96X & TX-97X Radio Remote Control Transmitter
2G-4080	Structured Mining Systems	Models TX-CMXX & TX-HSS Transmitter Assemblies
2G-4164	Techno Tools	Model 69370 Combustible Gas Leak Detector
2G-4126	Thermo MIE	Model PDR-1000AN
2G-3841	Thomas Instruments	Model 105 Blasters Digital Ohmmeter
2G-4122	Thomas Instruments	Model 106 Permissible Blaster's Digital Ohmmeter
2G-3668	TIF Instruments, A United Dominion Company	Model TIF 8800, Combustible Gas Detector
2G-2880	TRIPLETT CORP	Model 60, TYPE 2, Volt Ohmmilliammeter
18-A070020	Turboflare International	Model Turboflare Electronic Flare
2G-3941	Wellbore Navigation Inc	Model Welnav PeeWee SS Single Shot Magnetic Survey System
18-A050002	Wizard Devices	Model DSL Blasting Circuit Tester

Part 19 – Electric Cap Lamps (available)

Approval	Company	Description/Model
6D-36	Koehler	Model 5200
19-A110001	Koehler - Bright Star	Model Cordless Wheat Cap Lamp
19-A040001	Koehler - Bright Star	Wheat Li-16 Electric Cap Lamp System
19-A080001	Mine Site Technology	ICCL Integrated Comm Cap Lamp w Optional Tag & PED
6D-46	Mine Site Technology	4V, Battery Pwrd Model PED1 Permissible Paging Receiving Cap lamp
19-A100001	NL Technologies	Model Polaris All in One Cap Lamp Assembly
19-A080002	NL Technologies	Model Eclipse Cap Lamp Assembly
19-A040002	Rupprecht & Patashnick (now Thermo Fisher)	Model 3600 Personal Dust Monitor w Integral Cap Lamp
19-A100002	Xerebrus	Model Flare XM-1 Cap Lamp
19-A090001	New Wisdom	Model KL5M Cap Lamp

Part 20 – Flashlights (available)

Approval	Company	Description/Model
20-A120001	Eveready Battery	MSHD3AA LED Flashlight Assembly
20-A060004	Eveready Battery	MS2DLED Flashlight
20-A060003	Eveready Battery	MS2AALED Flashlight
10C-634	Eveready Battery	Model 1259 Flashlight
10C-634	Eveready Battery	Model 1359 Flashlight
10C-651	Koehler-Bright Star	200301 Flashlight
10C-650	Koehler-Bright Star	200201 Flashlight
10C-643	Koehler-Bright Star	Model 19301
10C-642	Koehler-Bright Star	Model 19101
20-A110002	NIOSH (Occupational Safety)	Gen4 LED Mine Light Assembly
20-A040001	Pelican Products	2620 permissible flashlight (headlamp)
20-A030001	Pelican Products	2610 headlamp
10C-649	Pelican Products	M10-8040 Flashlight
10C-641	Pelican Products	Model 2600 Heads Up Lite Flashlight
10C-637	Pelican Products	Model 2300 Super Duper Mitylite II Flashlight
10C-629	Pelican Products	Super Sabrelite Flashlight (now the 2000)
10C-628	Pelican Products	Super Pelilite Flashlight (now the 1800)
10C-633	Pelican Products	Model 2400 Flashlight
10C-630	Rayovac (now Spectrum Brands)	Model IN2-MS Permissible Flashlight
20-A100001	Streamlight	Survivor LED Flashlight Assembly
20-A070001	Streamlight	3AA Haz-Lo Portable Headlight Assembly
10C-648	Streamlight	2AA
20-A060002	Streamlight	4AA Propolymer Luxeon Flashlight Assembly
20-A060001	Streamlight	3C Propolymer Luxeon Flashlight Assembly
10C-658	Streamlight	680200 (lamp) and 680100 (LED) 4AA Flashlights
20-A110003	Venture Design Services	PWAP LED Light

Part 22 – Methane Detectors (available)

Approval	Company	Description/Model
8C-51	Appalachian Electronics Insts (AEI)	Model 101A
22-A110001	CSE Corporation	G4 Multi-gas monitor
22-A100001	Draeger Safety	X-aM 5000 Multi-gas monitor
22-A040003	Draeger Safety	PAC Ex2 Pump
22-A080001	Draeger Safety	X-AM 2000 Multi-gas monitor
22-A050001	Draeger Safety	X-aM 3000 Four Gas monitor
22-A120001	Industrial Scientific	Ventis MX4 Multi-gas monitor
22-A080002	Industrial Scientific	MX6 iBRID Multi-gas monitor
8C-76	Lumidor Safety Products	Micromax Pro-M Multiple gas detector
22-A040001	Mine Safety Appliances	Solaris Multi-gas detectors
22-A060001	Schauenburg Flexadux	Observer Multi-gas detection instrument

Part 23 – Communications and Tracking (available)

Approval	Company	Description/Model
23-A070007-0	American Mine Research	Model Mine Net Tag
23-A090014-0	American Mine Research	Model 6210 Mine Net Messenger 2-way text messaging device
23-A100001-0	American Mine Research	MN-6215 Dual Channel Wireless Transceiver
23-A090013-0	American Mine Research	MN-6000 Mine Net System
23-A040001-0	Audio Pack (made for Draeger)	Model BG4 Amplifier
23-A080003-0	Becker Electronics	Becker Leaky Feeder System
23-A090004-0	Becker Electronics	Becker Vehicle Tag BEC004
23-A090006-0	Becker Electronics	Becker Helmet Tag BEC003
23-A100010-0	Becker Electronics	VFMR-100; UFMR-100 Portable Radios
23-ISA090001-0	Becker Electronics	BEC002
23-ISA100001-0	Becker Electronics	TCT0 234 and TCT0 334 Cap Lamp Tags
23-ISA100002-0	Becker Electronics	TCT1-4XX Cap Lamp Tag
23-A080011-0	Conspec Controls	911152 Personnel Tracking Transmitter
23-A080006-0	Extronics	Model iTAG100/BWH3000 Tag
23-ISA080005-0	Innovative Wireless Technologies	Fixed Mesh Node with Antenna & Battery
23-A120005-0	Innovative Wireless Technologies	Model Sentinel Mesh Handset Two-Way Radio
23-A080016-0	Innovative Wireless Technologies	Sentinel Wireless Mesh Comm System
23-A100007-0	Innovative Wireless Technologies	Sensor Mesh Interface System
23-A120001-0	Innovative Wireless Technologies	Model SENTINEL Beacon
23-A110001-0	InSet Systems	10000000AA-00 Tracking, Voice and Test Comm System
23-A060002-0	Kenwood USA Corp	TK-290; TK-390
23-A100009-0	Kutta Radios	DRUM 100P Portable MF Radio
23-A090010-0	Kutta Technologies	DRUM 100R MF Comm System
23-A110003-0	Kutta Technologies	DRUM TTR-100 Tracking Tag Receiver
23-A110004-0	Kutta Technologies (Kutta Radios)	Model 100S UHF/VHF Comm System
23-A080015-0	L-3 Communications	ACCOLADE
23-A080020-0	L-3 Communications	ASM100001 Accolade Miner Mesh Radio Handset
23-A090015	L-3 Communications	ACCOLADE Tracking Beacon
23-A090017-0	L-3 Communications	TTTR-01 Tru-Tracker Tag Reader
23-A120003-0	L-3 Communications	Miner Mesh Locator (MML)
23-A110002-0	Lockheed Martin Corp	Model 03538-MCS-UP-001
23-A060001-0	Marco North America	Model PRIM PTT-1
23-A080013-0	Matrix Design Group	MDG METS 2.1
23-A060003-0	Matrix Design Group	Model Matrix Tracker T1000 RFID Tag
23-A090007-0	Matrix Design Group	P/N: 2WC-T
23-A100011-0	Matrix Design Group	Two-Way Communicator Handheld Tracker P/N: 2WC-HT
9B-219-0	Mine Radio Systems	Flexcom Communication System
23-A120004-0	Mine Radio Systems	Model MultiCOM Leaky-Feeder Comm System
23-A070006-0	Mine Radio Systems	Model TP2/ISPT
23-ISA080001-0	Mine Site Technologies	ICCL w Optional Tracker
23-ISA080002-0	Mine Site Technologies	ICCL w Optional PED
23-ISA080004-0	Mine Site Technologies	ICCL w optional T3100 tracker
23-A080012-0	Mine Site Technologies	T3i-SC RFID
23-A100003-0	Mine Site Technologies	IMPACT IS Comm System
23-A100006-0	Mine Site Technologies	MP70 MinePhone
23-A090003-0	Minecom (Division of TR Corp)	MCA 1000 VHF Leaky Feeder System
23-A090001-0	Minecom (Division of TR Corp)	MCA 2000 UHF Leaky Feeder System
23-A080007-0	Motorola	HT750
23-A110005-0	NewTrax Technologies	Network Infrastructure Device
23-ISA110001-0	Northern Lights Technologies	Model GII
23-ISA0700010	Northern Lights Technologies	Model GII Cap Lamp with RFID Tag
23-ISA070004-0	Northern Lights Technologies	Model GII Cap Lamp Messenger Circuit
23-A070001-0	Northern Lights Technologies	Model Standalone WiFi RFID Tag
23-A080010-0	Northern Lights Technologies	Digital Communications System
23-A100004-0	Northern Lights Technologies	Portable Access Node
23-A120002-0	Northern Lights Technologies	Model Ranger WiFi Phone
23-ISA070001-0	Northern Lights Technologies	Model WiFi Tag Circuit
23-A080004-0	Pyott-Boone	Model 1980 Tracking Tag
23-A090011-0	Pyott-Boone	Tracker Boss
23-A090012-0	Rajant Corporation	Breadcrumb WE-IS UX-2400
23-A100005-0	Special Electronics & Design	Rescom Modular Intercom System
23-A070005-0	Tunnel Radio of America	Model UltraComm Distributed Antenna Comm System
23-A080005-0	Tunnel Radio of America	Model MineAx T1 RFID Tracking Tag
23-A100002-0	Tunnel Radio of America	Model TR-MX-332 MineAx Tracking System
23-A050001-0	Varis Mine Tech	Model IS Leaky Feeder Comm System
23-A080001-0	Venture Design Group	MineTracer Miner Location Monitoring System
23-A070003-0	Venture Design Services	MLT Mobile Location Transponder Tag
23-A080002-0	Venture Design Services	Model TMLT Text Messaging Location Transponder
23-A080018-0	Wavetrend Technologies	Wavetrend Technologies
23-A100008-0	Argon ST	StratCommTrac Model C201 Subsurface Comm System
23-A100012-0	Argon ST	StrataComm Trac Model C202 Miner Communicator
23-A080017-0	Active Control Technology	ActiveMine Ekahau T301
23-A090002-0	Active Control Technology	ActiveMine AM1000 Wireless Mesh Comm System
23-A090002-0	Active Control Technology	ActiveMine AM2000
23-A090008-0	Active Control Technology	Model 8035 Telephone (SpectraLink 8030 phone & ACT001 Battery)

Listing of IEC-certified portable equipment that meet IS criteria approximately equivalent to those for MSHA approval, but are not also MSHA approved (current as of July, 2012)

This information supplements the subsection: 3.1.3 Identifying IEC-certified IS portable devices that meet criteria most nearly equivalent to those for MSHA approval, but are not also MSHA approved.

Item number 2 is ATEX certified for Group I M1, but is not IEC certified; ** indicates three devices identified that do not have MSHA-approved functional equivalents

IEC-certified portable equipment that meets IS criteria

Item Number	Category	Device	Model	Applicant	IEC Marking
**1	Imaging	Camera	iCAM501, 501U	Extronics (UK)	Ex ia I Ma
**2	Mobile Computing	Personal Data Assistant PDA	Iroc 623-ExEU-ATEX M1 mining certified industrial PDA (IBEx U)	ecom (DE)	ATEX: IBExU 04 1200 I M1 EEx ia I FM approval: Class 1 Division 1 Groups A-D
3	Analysis and Measurement	Data Collector	DC-225-IS	SKF Condition Monitoring (UK)	Ma Ex ia I; Ga Ex ia IIC
4	Analysis and Measurement	Radiation Monitor	T206 Potash Monitor	Tracerco (UK)	Ex ia I
5	Analysis and Measurement	Gas Detection	LQG 00xx	Drager Safety (DE)	Ex ia d I/IIC T4/T3
6	Analysis and Measurement	Gas Monitor	GasBadge Pro	Industrial Scientific (US)	Ex ia I
7	Analysis and Measurement	Data Logger	IS logger	Ringway Holdings (AU)	Ex ia I IP55
8	Analysis and Measurement	Monitoring	PSS 7000 Bodyguard	Draeger Safety (UK)	Ex ia I/IIC T4
9	Analysis and Measurement	Monitoring	Tell-Tale System	Golder Associates (UK)	Ex ia I
10	Analysis and Measurement	Air sampling pump	AirChek 3000	SKC Ltd (UK)	Ex ia I Ma; Ex ia IIC T4 Ga
11	Analysis and Measurement	Data logger	MS4##	DMT GmbH (DE)	Ex ia I Mb
12	Analysis and Measurement	Personal Air sampler	Tuff Personal Air Sampler	Casella (UK)	Ex ia I Ma
13	Analysis and Measurement	Noise Dosimeter	CEL-35X/IS dBadge Series Noise Dosimeter	Casella (UK)	Ex ia I Ma
14	Analysis and Measurement	Wireless Tilt Monitor Type 1	Wireless Tilt Monitor Type 1	CSIRO (AU)	Ex ia I IP55
15	Analysis and Measurement	Slim Borehole Scanner type SBS	Slim Borehole Scanner type SBS	DMT (DE)	Ex ia I Ma
16	Analysis and Measurement	Portable Gas Detector	Portable Gas Detector X-am 5600	Drager Safety AG (DE)	Ex ia I Ma
17	Analysis and Measurement	Pump	Model Pac Ex2 Pump	Drager Safety AG (DE)	Ex ia I/IIC T4
18	Analysis and Measurement	Command Transmitter iBz 83	Command Transmitter iBz 83	Eickhoff Bergbautechnik (DE)	Ex ia I
19	Analysis and Measurement	Temperature Measurement	Temperature Measuring Instrument TMG ###	Ing. Buro Jansen Marketing & Engineering (DE)	Ex ia I Ma
20	Analysis and Measurement	Pressure Transmitter	Pressure Transmitter type DMG/###I######	Ing. Buro Jansen Marketing & Engineering (DE)	Ex ia I Ma
21	Analysis and Measurement	Flash Card Recorder	Flash Card Recorder Monitoring System FCR 001 D	Mining Consultancy Services (AU)	Ex ia I IP55
22	Analysis and Measurement	air Flow Monitor	Accutron Plus IS Airflow Monitor	NLT Australia (AU)	Ex ia I
23	Analysis and Measurement	EC Detector	FTD-3000 Wireless LEL or EC Detector	RAE Systems (US)	Ex ia I
24	Analysis and Measurement	Deadline Checker	Deadline Checker TX5054	Trolex Ltd (UK)	Ex ia I
25	Analysis and Measurement	Sensor/Transmitter	Sentro Sensor/Transmitter TX635x.01i.xx	Trolex Ltd (UK)	Ex ia I Ma
26	Communications	Remote control	L0SL Shearer	Pempek (AU)	Ex ia I
27	Communications	Remote control	L0K2 pancake	Pempek (AU)	Ex ia I
28	Communications	Remote control	P-945	Bucyrus (UK)	Ex ia I (ExTR)
29	Communications	Remote control	Bi-Di Radio	Controlled Systems (UK)	Ex ia I
30	Communications	Remote control	Radio Remote Control	Cavotec Micro-Control (NO)	Ex ia I/IIB T4
31	Communications	Remote control	RS20s Shield Mover	Joy (UK)	Ex ia I
32	Communications	Radio	m-Comm	Golder Associates (UK)	Ex ia I (H2) Ma Ta
33	Communications	Headset series	Tactical XP	3M Svenska AB (SE)	Ex ia I Ma
34	Communications	Headset series	Lite-Com Pro II	3M Svenska AB (SE)	Ex ia I Ma
35	Communications	Wireless Router	Wireless Router Access Point/WRAP 2XX	3M Svenska AB (SE)	Ex ia I Ma
36	Communications	Radio	460 MHz PSS Merlin Portable Radio	Draeger Safety Ltd (UK)	Ex ia I / IIC T4
37	Communications	Radio	UG Mine Radio MM8K	Matsushima Electrical Machinery (JP)	Ex ia I
38	Communications	Wireless Network Switch	NS40: IS Wireless Network Switch	Mine Site Technologies (AU)	Ex ia I IP65
39	Communications	Transceiver	Portable IR Transceiver Part 2079	Monduran Pty (AU)	Ex ia I
40	Communications	WiFi Phone	Dyna WiFi Phone	NL Technologies (CA)	Ex ia I IP55
41	Communications	Wireless Access node	IS Wireless Access Node	NLT Australia (AU)	Ex ia I
42	Tracking	RFID tag	ARFID Tags	Blue Glue (AU)	Ex ia I
**43	Tracking	Bar Code Scanner	CK32IS	Intermec Technologies (US)	Ex ia I / IIC T4
44	Tracking	Tag	TVT0 ### Vehicle Tag	Becker Electronics (SA)	Ex ia I Ma
45	Tracking	Active Tag Reader	UATR 400/430 IS Active Tag Reader	Becker Electronics (DE)	Ex ia I Ma
46	Tracking	Personal Locator	Portable Device w Personnel Location MMLK	Matsushima Electrical Machinery (JP)	Ex ia I IP54
47	Tracking	IS RFID Reader	IS RFID Reader	NLT Australia (AU)	Ex ia I
48	Tracking	Tag	L-TG100 Wavetrend Tag	NLT Australia (AU)	Ex ia I
49	Lighting and Alarms	Flashlight	Torch R-5X	Wolf Safety Lamp (UK)	Ex ia I/IIC T4 IP67
50	Lighting and Alarms	Monitoring	Bodyguard II BG4	Drager Safety Pacific (AU)	Ex ia I/IIC T4
51	Lighting and Alarms	Alarm Amplifier	AAC 00##	Drager Safety (DE)	Ex ia I Ma
52	Lighting and Alarms	Headlight	IS Headlight	Everyready (US) [Sonco (China)]	Ma Ex ia I / Ga Ex ia IIC T4
53	Lighting and Alarms	Alarm	IS Piezo Alarm ALT3	Austdac Pty (AU)	Ex ia I Ma
54	Lighting and Alarms	Signaling Device	Acoustic signaling device SD-04/1	Elektrometal S.A. (PL)	Ex Ia Ma
55	Lighting and Alarms	Caplight	Type G L16 Caplights	Enersys (US)	Ex I
56	Lighting and Alarms	Cordless Cap Lamps & Helmet Lamps	Cordless Cap Lamps & Helmet Lamps	Kinyun Australia (AU)	Ex ia I IP67
57	Lighting and Alarms	Flashlight	Flashlight / Head Torch 2690	Pelican Products (US)	Ex ia I Ma
58	Miscellaneous	Ear Muff	SM1xSR	Sensear (AU)	Ex ia I Ma
59	Miscellaneous	Advanced Page Tuner Type 500-584	Advanced Page Tuner Type 500-584	Joy Mining Machinery (US)	Ex ia I
60	Miscellaneous	Transducer Simulator	RS20s Transducer Simulator	Joy Mining Machinery (US)	Ex ia I

ACRI2001 and corresponding ANSI/ISA IS standards topics not applicable to portable IS devices

(9 general topics covering a total of 68 ACRI2001 sections; analysis used ANSI/ISA 60079-0 and ANSI/ISA 60079-11 5^th Editions)

This information supplements the subsection: 4.2 Results and discussion (Comparison of ACRI2001 and IEC-based IS standards).

1. Maximum safe-area voltage, as the maximum voltage available to associated apparatus

ACRI2001 4.11          ANSI/ISA 60079-11  3.16

ACRI2001 8.7.1         ANSI/ISA 60079-11  5.2, 9

2. Maximum input voltage for normal conditions, for line-powered circuits

ACRI2001 5.2.1.2      ANSI/ISA 60079-11  3.8

3. Creepage and clearance distances, for circuit voltages over 1300 V

ACRI2001 7.1                        ANSI/ISA 60079-11  Table 5 and Annex F

4. Grounded partitions, with respect to strength and ampacity

ACRI2001 7.1.6         ANSI/ISA 60079-11  6.3.1

5. Encapsulation, used as an “alternate form of protection to intrinsic safety”

ACRI2001 7.2.1.3 Note          ANSI/ISA 60079-11  6.6

(ACRI2010 covers non-IS encapsulation, and ANSI/ISA 60079-18 covers non-IS encapsulation)

6. Transformers used as protective components, for supplying IS circuits; including spark ignition testing of circuits powered by constant voltage transformers, and dielectric strength testing of transformers for direct connection to a supply voltage

ACRI2001 8.2 through 8.2.5 (includes 14 sections)   ANSI/ISA 60079-11  7.3,  8.1.1,  8.1.2

ACRI2001 10.1.7.3                            ANSI/ISA 60079-11  5.1

ACRI2001 10.2.1.1 through 10.2.2.3 (includes 12 sections)  ANSI/ISA 60079-11  8.2,  10.10

7. Shunt diode barrier assemblies (diode safety barrier)

ACRI2001 8.7 through 8.7.8 (includes 16 sections)   ANSI/ISA 60079-11  5.2,  7.3,  8.4,  8.6.1,  9.1,  9.2.1,  9.2.2

ACRI2001 10.4.1 through 10.4.4.2 (includes 8 sections)       ANSI/ISA 60079-11  7.1 and 10.8

8. Relays, where IS and non-IS circuits are connected to the same relay

ACRI2001 8.10          ANSI/ISA 60079-11  6.3.13

9. Marking of additional IS apparatus, such as components of a system

ACRI2001 12.3 through 12.4.4 (includes 10 sections)           ANSI/ISA 60079-11  12.1,  12.2

ACRI2001 sections effectively equivalent to corresponding provisions in ANSI/ISA 60079-0 and 60079-11

(188 ACRI2001 sections; analysis used ANSI/ISA 60079-0 and ANSI/ISA 60079-11 5^th Editions)

This information supplements the subsection: 4.2 Results and discussion (Comparison of ACRI2001 and IEC-based IS standards).

1.0, 2.1, 2.2, 2.3, 3.1, 3.2, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 4.10, 4.12, 4.13, 4.15, 5.1.1, 5.1.2, 5.1.3, 5.1.4, 5.1.5, 5.2, 5.2.1, 5.2.1.1, 5.2.2, 5.2.3, 5.3, 5.3.1, 5.3.2, 6.1, 6.1.1, 6.1.2, 6.1.2.1, 6.1.2.1.1, 6.1.2.1.2, 6.1.2.1.3, 6.1.2.1.4, 6.1.2.2, 6.1.2.2.1, 6.1.2.2.2, 6.1.2.2.3, 6.1.3, 6.1.4, 6.2, 6.2.1, 6.2.2, 6.2.3, 6.3, 6.3.1, 6.3.1.1, 6.3.1.2, 6.3.1.3, 6.3.1.4, 6.3.1.5, 6.3.1.6, 6.3.1.7, 6.3.2, 6.3.2.2, 6.3.2.3, 6.3.3, 6.3.3.1, 6.3.3.3, 6.3.3.4, 6.3.3.5, 6.3.3.6, 7.1.1.1, 7.1.1.2, 7.1.1.3, 7.1.2, 7.1.5, 7.1.7, 7.2.1, 7.2.1.1, 7.2.2, 7.2.3, 7.2.3.1, 7.2.3.2, 7.2.4, 7.3, 7.3.1, 7.3.2, 7.3.2.1, 7.3.2.2, 7.3.2.3, 7.3.4, 7.3.5, 7.4, 7.4.1, 7.4.2, 7.4.3, 7.4.4, 8.1, 8.3, 8.4, 8.5.1, 8.6, 8.6.1, 8.6.3, 8.6.5, 8.8, 8.8.1, 8.8.2, 8.9.1, 8.11.1.1, 8.11.1.2, 8.11.1.3, 8.11.2.1, 8.11.2.2, 8.11.2.3, 8.11.2.4, 8.11.2.4.1, 8.11.2.4.2, 8.11.2.4.3, 8.11.2.4.4, 8.11.2.4.5, 8.11.2.4.6, 8.11.2.5, 8.11.3.1, 8.11.3.2, 8.11.3.3, 9.1.2, 9.3, 9.3.2, 9.3.3, 9.3.4, 9.3.5, 9.3.7, 9.3.8, 9.3.8.1, 9.3.8.2, 9.3.8.3, 9.3.9, 9.3.10, 9.3.10.1, 9.3.10.2, 9.3.10.2.1, 9.3.10.2.3, 9.3.10.2.4, 9.5.1, 10.1.1.1, 10.1.1.2, 10.1.2.1, 10.1.2.1.1, 10.1.2.1.2, 10.1.2.1.3, 10.1.3.1, 10.1.3.2, 10.1.3.2.1, 10.1.5.1, 10.1.5.2, 10.1.5.4, 10.1.7.1, 10.5.1, 10.5.2, 10.5.3, 10.5.4, 10.5.5, 10.7.1, 10.7.1.1, 10.7.1.2, 10.7.1.3, 10.7.2, 10.8, 10.9, 10.10.1, 10.10.1.1, 10.10.1.2, 10.10.1.3, 10.14.1, 10.15.1, 10.15.2, 10.15.3, 11.0, 12.0, 12.1., 12.1.1, 12.1.2, 12.1.3, 12.1.4, 12.5, 12.6, 12.7.1, 12.7.1.1, 12.7.1.2, 12.7.2

ACRI2001 sections less restrictive than corresponding provisions in ANSI/ISA 60079-0 and 60079-11

(total of 44 ACRI2001 sections covering 17 topics; analysis used ANSI/ISA 60079-0 and ANSI/ISA 60079-11 5^th Editions)

This information supplements the subsection: 4.2 Results and discussion (Comparison of ACRI2001 and IEC-based IS standards).

ACRI2001 4.11          ANSI/ISA 60079-11  3.16

Maximum safe-area voltage with respect to associated apparatus: Possible damage due to charging (in a non-classified area) is considered by ANSI/ISA, but not explicitly by MSHA

ACRI2001 5.4                        ANSI/ISA 60079-11  5.2, 10.1.3.2

MSHA specifies a safety factor of 1.5 on energy for normal operation and one-fault analyses; ANSI/ISA applies an equivalent safety factor for resistive circuits, and has requirements that result in a safety factor of 2.25 on energy for capacitive and inductive circuits

ACRI2001 6.3.2.1      ANSI/ISA 60079-11  7.6,  10.1.2

Criteria for countable faults: A spark test connection is not considered a countable fault by ANSI/ISA, but it is by MSHA (when creepage and clearances distances are met)

ACRI2001 6.3.3.2      ANSI/ISA 60079-11  10.6,  10.1.2

Securing shunt protective components: ANSI/ISA allows only encapsulation, while MSHA permits other techniques

ACRI2001 7.1                        ANSI/ISA 60079-11  Table 5

Creepage and clearance distances: ANSI/ISA uses peak voltages to determine creepage and clearance distances, while MSHA uses nominal rms voltage for creepage distances; also, ANSI/ISA CTI values are more conservative than MSHA CTI values below 1300V

ACRI2001 7.1.4         ANSI/ISA 60079-11  6.3.1.1

Considering non-countable shorts between several adjacent conductors: ANSI/ISA has no limit on the number of adjacent conductors shorted as non-countable faults, but MSHA allows certain combinations to be considered a countable fault

ACRI2001 7.5.6         ANSI/ISA 60079-0  5.3.2.1

Temperature limit for exposed components: ANSI/ISA does not allow the surface temperature of an exposed component to exceed 150°C, while MSHA does with additional testing

ACRI2001 8.4.1         ANSI/ISA 60079-11  7.1,  8.4

Rating of current limiting resistors: ANSI/ISA does not allow current limiting resistors to operate above 2/3 their power rating, while MSHA does if other criteria are met

ACRI2001 8.5.2        ANSI/ISA 60079-11  8.5.1

Blocking capacitor rating: ANSI/ISA always requires a 500 V test for blocking capacitors, while MSHA does not under certain circumstances

ACRI2001 8.6.2        ANSI/ISA 60079-11  8.6.1,  8.6.2

Securing shunt protective components: ANSI/ISA allows only encapsulation, while MSHA permits other techniques

ACRI2001 8.6.4        ANSI/ISA 60079-11  7.6 Part H,  8.6.1

Protecting shunt protective components: ANSI/ISA allows only encapsulation, while MSHA permits other techniques

ACRI2001 8.6.6        ANSI/ISA 60079-11  7.5.2

Semi-conductor component current rating: ANSI/ISA requires that protective semi-conductor components not exceed 2/3 their rating under short circuit fault conditions, MSHA requires only that their rating be adequate for the fault condition

ACRI2001 9.1.1        ANSI/ISA 60079-11  7.1

Discrete component current rating: ANSI/ISA requires that discrete components not exceed 2/3 their rating under fault conditions, but MSHA specifies that they not exceed 2/3 their rating only under normal conditions

ACRI2001 9.1.3        ANSI/ISA 60079-11  7.1

Components operated at levels above their rating: ANSI/ISA does not consider use of components at levels above 2/3 their rating, while MSHA would allow exceeding their rating with additional testing

ACRI2001 9.3.1        ANSI/ISA 60079-11  7.4.2

Battery and battery cell requirements: ANSI/ISA outlines requirements more specific than MSHA requirements

ACRI2001 9.3.11 through 9.3.13 (includes 7 sections)           ANSI/ISA 60079-11  7.4.8

External battery-charging contacts: ANSI/ISA allows fewer options than MSHA for ensuring energy is limited at external battery-charging contacts

ACRI2001 9.5.2        ANSI/ISA 60079-11  5.3.2.1

Component thermal considerations: ANSI/ISA does not allow component surface temperatures above 150 degrees C, but MSHA does with additional testing

ACRI2001 9.6           ANSI/ISA 60079-11  8.4 Note

Thermal considerations for incandescent lamps: ANSI/ISA does not allow heated filament lamps in IS devices, while MSHA does

ACRI2001 10.1.2.2 through 10.1.2.3 (includes 4 sections)    ANSI/ISA 60079-11  10.1.4.2

MSHA specifies a safety factor of 1.5 on energy for spark ignition tests: ANSI/ISA requirements for spark ignition tests result in safety factors higher than MSHA for some circumstances

ACRI2001 10.3.1 through 10.3.3 (includes 6 sections)          ANSI/ISA 60079-11  7.1, 8.4

Current limiting resistor tests: ANSI/ISA requires that all resistors operate at no more than 2/3 their rating, under normal or fault conditions, while MSHA would allow operation at over 2/3 rating under some circumstances

ACRI2001 10.5.6       ANSI/ISA 60079-11  5.6.3

Wire temperature requirements and testing: ANSI/ISA has wire temperature requirements that are more specific and conservative than MSHA requirements

ACRI2001 10.11 through 10.11.4 (includes 5 sections)         ANSI/ISA 60079-11  5.3.2.1

Component surface temperature: ANSI/ISA allows component surface temperature to exceed 150 degrees C only if the device is in an enclosure to exclude coal dust, while MSHA will allow temperatures over 150 degrees C with additional testing

ACRI2001 10.12 through 10.12.2 (includes 3 sections)         ANSI/ISA 60079-11  8.4 Note

Heated filament lamp breakage testing: ANSI/ISA does not allow heated filament lamps in IS devices, while MSHA does

ACRI2001 10.14.2     ANSI/ISA 60079-11  10.6.1

Testing of encapsulant: ANSI/ISA requires an impact test for unprotected encapsulant, while MSHA requires only a static mechanical strength test

Assumptions, data, and calculations used for estimating IS device exposure in U.S., Australian, and South African coal mines

This information supplements the subsection: 5.1 Methods (Comparison of ACRI2001 and IEC IS standards safety records).

(Websites listed were accessed 7-26-16)

Exposure of IS-devices to the mine environment was estimated using the number of miners, the number of hours worked in underground coal mines, and the number of devices carried underground.

Exposure estimate for U.S. mines

MSHA data indicate that during 2010 there were 38,166 underground coal miners in longwall and continuous miner operations. On average, an underground coal miner worked 2,325 hours per year (based on 38,166 miners working 88,728,114 hours in 2010, according to MSHA data)[1].  If each miner carried three portable, IS-devices[2] (a communications device, a tracking device, and a gas detector), exposure is calculated as follows.

38,166 miners X 3 devices/miner X 2,325 hours/year ≈ 270 X 10⁶ device-hours/year

Exposure estimate for Australian mines

Australian data indicate that during 2011 there were approximately 16,000 underground coal miners in longwall and continuous miner operations.[3]^,[4]  Based on input from industry[5]^,[6] and government[7] sources,  assume 50% of underground coal miners carry a combination cap lamp/tracking device, and deputies (foremen), in addition, carry 1 gas detector  and 1 communications device.  If we further assume that miners work approximately 2,000 hours per year, and that approximately 800 foremen staff the 200 underground operating sections reported for 2011,[8]^,[9] exposure is calculated as follows.

[8,000 (50% of 16,000) miners X 1 device/miner X 2,000 hours/year]

+ [800 foremen X 2 devices/foreman X 2,000 hours/year] ≈ 20 X 10⁶ device-hours/year

Exposure estimate for South African mines

Available information on South African underground coal mining indicates that 19,000 underground coal miners worked in longwall and continuous miner operations during 2010.[10]  A knowledgeable industry source[11] estimated gas detector usage at approximately 5% of the total underground coal mine workforce, two-way communications device usage at 10%, electronic tracking devices at 10%, and collision avoidance devices at 10%.  This allows estimates of approximately 950 gas detectors, 1900 communications devices, 1900 electronic tracking devices, and 1900 collision avoidance devices, for a total of 6,650 portable IS devices carried underground.  Assuming underground coal miners work 2,000 hours per year, exposure is calculated as follows.

6,650 devices X 2,000 hours /year ≈ 13 X 10⁶ device-hours/year

IECEx-approved Certification Bodies

This information supplements the subsection: 3.1.2 IEC certification of portable IS devices; concepts, terminology, and labeling.

The following organizations have successfully completed the IECEx assessment process and are approved to operate within the IECEx Certified Equipment Scheme and to issue IECEx Test Reports (EXTRs), IECEx Quality Assessment Reports (QARs) and the Online Certificate of Conformity. As of July, 2012; International Electrotechnical Commission System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres (IECEx System) provided a list of approved Certification Bodies: (accessed 7-26-16)

Australia

• SIMTARS - Safety in Mines Testing and Research Station
• TSA - TestSafe Australia
• TRA - TUV Rheinland Australia Pty., Ltd

Brazil

• NCC - Associação NCC Certificacões do Brazil

Canada

• CSA - CSA International
• QPS - QPS Evaluation Services Inc.

China

• CQM - China Quality Mark Certification Group Co., Ltd

Croatia

• EXA - Agencija za prostore ugro�ene eksplozivnom atmosferom (Ex-Agencija)

Czech Republic

• FTZU - Fyzikáln technický zkušební ústav (Physical Technical Testing Institute)

Denmark

• UL/DEMKO - UL International DEMKO A/S

Finland

• VTT - VTT Expert Services Oy

France

• INERIS - Institut National de l'Environnement Industriel et des Risques

• LCIE - Laboratories Central des industriesElectriques International

Germany

• BV - Bureau Veritas Consumer Products Services Germany GmbH
• DEKRA EXAM GmbH - DEKRA EXAM GmbH
• IBExU - IBExU Institut für Sicherheitstechnik GmbH
• PTB - Physikalisch-Technische Bundesanstalt
• TÜV NORD - TÜV NORD CERT GmbH
• TÜV Rheinland - TÜV Rheinland Industrie Service GmbH
• TÜV SÜD - TÜV SÜD Product Service GmbH
• ZELM - ZELM Explosionsschutz GmbH

Great Britain

• BAS - BASEEFA Ltd
• FM UK - FM Approvals
• ITS - Intertek Testing and Certification Ltd
• SIRA - SIRA Certification Service
• TRC - TRaC Global Ltd

Hungary

• BKI - ExVÁ Testing Station for Explosion Proof Equipment

Italy

• CESI - Centro Elettrotecnico Sperimentale Italiano S.p.A.
• IMQ - Istituto Italiano del Marchio di Qualità S.p.A

Korea

• KGS - Korea Gas Safety Corporation
• KOSHA - Korea Occupational Safety and Health Agency
• KTL - Korea Testing Laboratory

Netherlands

• DEKRA - DEKRA Certification B.V.

Norway

• DNV - Det Norske Veritas AS
• NEMKO

Poland

• KDB - Central Mining Institute, Product Certification Team BARBARA

Russia

• NANIO CCVE - Central Mining Institute, Product Certification Team BARBARA

Slovenia

• SIQ - Slovenian Institute of Quality and Metrology

Sweden

• SP - SP Technical Research Institute of Sweden

Switzerland

• Electrosuisse

United States

• ITS - Intertek Testing Services NA, Inc.
• FM - FM Approvals LLC
• UL - Underwriters Laboratories Inc.

[1] Data from MSHA web site: https://arlweb.msha.gov/STATS/PART50/p50y2k/AETABLE.htm.

[2] Information regarding the IS-devices carried underground by US coal miners was obtained from telephone interviews with MSHA inspectors Donald Dean, New Stanton, PA (724-925-5150) and John Hayes, Morgantown, WV (304-225-6800).

[3] Annual Coal Statistics, Queensland Government, https://www.qld.gov.au/  

[4] NSW Mine Safety Performance Report 2009-2010, Appendix A-2, Fig 158, p106, https://www.resourcesregulator.nsw.gov.au/sites/default/files/documents/nsw-mine-safety-performance-report-2009-10.pdf

[5] Personal communication, James Cawley-Peter Henderson, Principal engineer, Xstrata Coal, NSW, phenderson@xstratacoal.com.au , May 17, 2012

[6] Personal communication, James Cawley-Bob Kearfott, Business Development Manager, Becker Mining America, Inc., Bob.Kearfott@us.becker-mining.com , May 29, 2012

[7] Personal Communications, James Cawley-John Waudby, Senior Inspector of Electrical Engineering – Special Projects, Mine Safety Operations, NSW Department of Trade and Investment, Regional Infrastructure and Services, 8 Hartley Drive, Thornton, NSW 2322, PO Box 343, Hunter Regional Mail Centre, NSW 2310, john.waudby@industry.nsw.gov.au , May 20-21, 2012

[8] Business as usual? – Results of Global Continuous Miner & Bolter Miner Census 2008, Arne K. Bayer, Karl Nienhaus, Manuel Dangela, Glückauf Mining Reporter, February 2009, pp. 8-14

[9]  Australia’s longwall mines 2011 review, statistics section,  International Longwall News, http://www.internationalcoalnews.com/

[10] Department of Mineral Resources, Republic of South Africa. 

[11] Personal communication, James Cawley-Bob Kearfott, Business Development Manager, Becker Mining America, Inc., Bob.Kearfott@us.becker-mining.com , June 5, 2012

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