An improperly maintained diesel engine can emit undesirable concentrations of exhaust emissions compared to a well-maintained diesel engine. The Mine Safety and Health Administration (MSHA) has promulgated a new regulation that will require underground coal mine operators to perform weekly emission tests on specific diesel-powered equipment (3). To allow the mine operator latitude in performing these tests, MSHA outlined test performance criteria in the regulation but did not specify a test procedure (Appendix A). This report describes an emissions-assisted maintenance procedure, or EAMP, that can be used to comply with the MSHA regulation. The EAMP determines if a diesel engine requires maintenance based upon concentrations of gaseous species in an engine's exhaust.

Detecting a need for engine maintenance based upon a diesel engine's exhaust is not a new concept. Numerous studies have identified relationships between exhaust emissions and engine faults (1,2,16,17,18,23,25), and various on-site emission test procedures have been developed to determine if there is a need for engine maintenance (2,13,18,23). However, none of these procedures are optimized to meet the requirements of the MSHA regulation. The MSHA regulation requires that underground coal mine operators perform weekly loaded-engine emission tests on all permissible and heavy-duty, nonpermissible, diesel-powered mine equipment. These tests are to be set up, performed, recorded, and interpreted by mine equipment maintenance personnel. The MSHA test performance criteria should be met if the test procedure has the following characteristics.

• The procedure should be accurate, precise, and reproducible. A procedure that identifies trends in engine emission concentrations over time will help indicate a need for maintenance.
• The test instrument used to sample, measure, display, and record the emission data should be rugged and portable.
• Instrument set-up, test interval, and data interpretation should take no more than 1 half-hour per engine.
• Mine equipment maintenance personnel should be able to understand, conduct, and interpret the test procedure easily.

The EAMP was demonstrated to possess all these characteristics.

• Field tests demonstrated the reproducibility of the torque converter stall engine loading method and the accuracy and precision of the sampling and measurement methods. CO and CO2 measurements deviated less than 5% over repeated tests. Although the EAMP never detected CO concentrations that exceeded MSHA's CO limit of 2500 parts per million (ppm) (3), an induced air intake restriction was detected by an increase in CO from 250 to 900 ppm. Other elevated emission concentrations indicated that further engine inspection and possible maintenance were required.
• The portable emission analyzer was sufficiently rugged for the mine environment. However, the laptop computer used to log the analyzer data during the field tests was not suitable for the mine environment.
• Results from laboratory and field experiments indicated that the EAMP could be set up, tests run, results recorded, and data analyzed in 10 to 15 minutes per engine.
• In the field, engine maintenance personnel were trained to perform and interpret the EAMP in two 8-hr shifts. In a separate task a training manual will be developed to provide user-level information on test instruments and calibration, test set-up, engine loading, emissions sampling and recording, and data interpretation.