Skip directly to search Skip directly to A to Z list Skip directly to page options Skip directly to site content

NIOSHTIC-2 Publications Search

Search Results

Spark ignition probability estimates for resistor and inductor circuits in methane-air atmospheres.

Authors
Cawley-JC
Source
IEEE Trans Ind Appl 1988 Sep/Oct; 24(5):878-883
NIOSHTIC No.
10006597
Abstract
Safety factors are employed by the engineering profession to ensure that a margin of safety exists between engineering test conditions and the conditions of actual or anticipated use. The safety factor presently used by the Mine Safety and Health Administration (MSHA) to assess the safety of electronic circuits for use in methane-air atmospheres is a factor of 1.5 On energy at the point of test plus two worst-case faults. A precise knowledge of the degree of safety over and above the conditions of actual use obtained by using the 1.5 Factor, however, is not easily determined. The Bureau of Mines is engaged in intrinsic safety research that will ultimately relate the conditions of test and actual use by estimating the simple ignition probability, pi, versus current for circuits in an 8.3 pct methane-air atmosphere. The experimental design minimizes the probability of not observing an ignition that should occur during a series of tests. For resistive circuits in 8.3 pct methane-air mixtures, no ignitions were observed below 2,000 ma at 20 V DC, 350 ma at 30 V DC, 150 ma at 40 V DC, and 175 ma at 50 V DC. The simple probability of ignition corresponding to these currents is estimated to be, respectively, 1.0 X 10-6, 1.7 X 10-7, 3.0 X 10-7, and 1.0 X 10-5. Results for inductive circuits show that ignition was not obtained below 35 ma for 600 mh, 90 ma for 100 mh, 230 ma for 10 mh, and 700 ma for 1 mh, corresponding to an estimated probability of ignition of 3.8 X 10-6, 4.0 X 10-6, 2.0 X 10-6, and 3.3 X 10-7, respectively. The ignition mechanism seems to break down below
Keywords
Flammable-gases; Methanes; Ignition-sources; Mining-industry; Mine-shafts; Mine-gases; Electrical-hazards; Electrical-transmission
CODEN
ITIACR
CAS No.
74-82-8
Publication Date
19880901
Document Type
OP; Journal Article
Fiscal Year
1988
NTIS Accession No.
NTIS Price
Identifying No.
OP 5-89
Issue of Publication
5
ISSN
0093-9994
NIOSH Division
PRC
Source Name
IEEE Transactions on Industry Applications
State
PA
TOP