Prevention of Crankcase Explosions in Reciprocating Compressors

摘要

Three ignitions occurred in quick succession in the crankcase of a large,reciprocating, hydrocarbon gas compressor. Protective systems limited the effects and led to safe system shutdown. An investigation team found the ignition source to be an electrical discharge and resultant arcing, between the piston rod oil scraper rings and their housing. The insulating properties of the pad fitted between the non-drive end bearing and earth were found to deteriorate with time. A simple monitoring system was fitted to indicate the duration of the pad's effective life. Experimental work found that the double tangential rings used for low-pressure sealing were ineffective at pressures less than 0.5 bar, although they sealed well at higher pressures. These rings could be energized by the application of nitrogen buffer gas. In evaluating a proposal to replace these rings with side-loaded pressure rings to API 618, it was found that certain manufacturing quality and housing design features could reduce their sealing effectiveness to less than that of the original type. A manufacturing quality plan agreed with the manufacturer has overcome these problems. Modifications incorporating these findings have been applied to the compressor, and to three others, without any recurrence of the problem.