Reciprocating compressors are extensively used on high pressure and critical applications in all industries. These equipment needs through review of design of various components for a failsafe design. API-618 specifies various details about construction of various components, but due to OEM design by compressor vendor, proper review is not done or due to cost economic of equipment these are not given importance.
There are many examples when accident took place when these issues were ignored or correct assembly procedure for assembly of components is not followed and there were mistakes in design of piping system. In this paper, some of such cases are discussed and improvements are suggested for preventing any safety incidents. The issues described are designs of unloaders and venting system, unloader and vent piping, cylinder tap off connections, end clearance pocket unloaders, distance piece and crank case venting system, purge system for motors.
One of the risks with valve unloaders is the contamination of the instrument air with flammable gas specially on high pressure application. The instrument air may get contaminated with hydrocarbon if unloader leaking from stem and leak off gas tubing which is connected to flare may get interchanged with the instrument air connection. The same mistake if not noticed & compressor started, it may lead to the incident where compressor can show showed a strange vibration pattern, and instrument air header may get contaminated with hydrocarbon gases.
Another issue is crank case pressurisation due to improper venting system which can lead to pressurisation of crank case, failure of oil seals leading to flywheel end bearing failures. Further checking for finding reasons of crank case pressurisation, it is observed that excessive rod packing leaks results from incorrect leveling of compressor, distance and cylinders.
Motor purge system is one of the essential requirements for starting large reciprocating compressors; mistake in design/fabrication of vent system may create unsafe condition leading to explosion in motor.
All issues have been discussed in paper and various solutions and fail safe design have been suggested to improve safety and reliability. The studies also indicates that proper start up procedure and follow up of correct checklists during overhauling and start up can eliminate/ identify such mistakes.