Inspection of spark plugs removed from natural-gas compressor engines suggests an NOx-reduction system may extend spark-plug operating life beyond 2,000 hr.
The plugs were removed from compressor engines at stations operated by CNG Transmission Corp. after more than 2,000 hr of operation. The NOx-reduction system installed on these engines is from ENOX Technologies Inc., Natick, Mass.
Three sites
Analysis of the plugs was by Stitt Spark Plug Co., Conroe, Tex., which was also the original supplier.
The plugs were removed from a Clark TCV-10 engine at CNG Transmission's Ellisburg, Pa., station. Plugs were also pulled at stations in Leidy and Sabinsville, Pa.
Stitt has said that the plugs analyzed could have run another 1,000-2,000 hr had they not been destroyed in analysis. The analysis showed minimal gap erosion.
CNG Transmission says that 2,000 hr of use is always a target for newly installed ignition systems but rarely reached. The company says that some plugs not pulled for analysis were checked at 1,000 hr of operation and showed only 0.002-0.003 in. erosion. These plugs have run more than 2,500 hr to date.
In late 1994, the INOx System was installed in a $10 million project in 53 compressor station engines in Pennsylvania and New York (OGJ, Sept. 26, 1994, p. 91).
The system, according to ENOX Technologies, allows compressor-station engines to burn leaner air/fuel mixtures. It reduces NOx emissions by ensuring lean-burn combustion.
The product consists of a patented PlasmIgnition System, auxiliary system modifications, and turbo-charging to provide the excess air needed to complete the low-NOx operation.
Plasma technology produces a continuous electrical plasma discharge much like the flame of a pilot light, instead of a conventional 50-sec spark within the gap of the plug.
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