and that the possibility for high concentrations of hydrogen sulfide existed. This could not be confirmed, though, as no fuel gas analysis had been made. It was confirmed, however, that the engine was not being operated with any lube oil anything like the lube oil the deposit chemistry suggested was being introduced into the power cylinders. More to the point, the operator could not confirm any excessive rates of lube oil consumption for the engine.

The source of the operating problem was pinpointed when the operating personnel remarked that the only device consuming excessive amounts of lube oil was the compressor which was used as part of the fuel delivery system so as to boost the low Btu gas to the engines. It was eventually confirmed that the fuel delivery compressor and its excessive rate of lube oil consumption was the mechanism responsible for the large incidence of spark plug fouling.

This plug was returned to us as one of a set of 12 that had operated for approximately 4000 hours in the fuel cells (pre-combustion chambers) of a turbocharged, four-stroke cycle, stratified charge, natural gas-fueled, stationary, V-angle, slow speed, 12-cylinder, integral compressor engine. The operating time on these spark plugs was regarded

as normal. The spark plugs were returned to us as part of an engineering evaluation control. We regard this spark plug's firing-end appearance as being typical of so many operating hours with a low ash lube oil, and include it primarily to provide a reference point for the Case A & B spark plugs.

We strongly advocate the regular examination of the spark plugs removed from service in any routine benchmarking of engine operation. At the very minimum, a careful visual examination of the spark plugs' firing-end appearances can identify power cylinders that may benefit from borescope (or other) inspection routines. If this analysis of "used" spark plugs is to be effective, the spark plugs removed from service must be logged as to their operating hours as well as to their engine location (i.e., cylinder #2R or cylinder #2R, intake side plug, for example, if a dual spark plug

cylinder). Furthermore, the full engine complement of spark plugs must be examined so that a comprehensive picture of cylinder norms can be developed, and so that exceptional appearances can be isolated based on the historical record. These diagnostic measures are based upon our requirements for our factory-conducted diagnostic services. Our experience indicates that this type of spark plug analysis is invaluable as a diagnostic medium and can provide operators with significant information