Written by Stephen H Shakeshaft
Sunday, 28 February 2010 15:05
Page 1 of 5
A client has two reciprocating gas compressors installed, the duty of which is to fill high pressure tube trailers for onward shipping by road to customers.
Despite the product being highly profitable, the client was unable to make full use of the available and proven production capacity from the factory due to the extremely unreliable high pressure compression section on the plant.
The compressors are two stage double acting reciprocating machines used to boost the gas pressure from 39 BarG to the desired 225 BarG.
The two installed compressors run continuously 24 hours per day and on occasions when there were no tube trailers to fill, the compressors continue to run, filling a high pressure storage facility that acts as a buffer between the machines and the tube trailers.
The compressors were originally supplied as oil lubricated machines with the piston rod packings and piston rings lubricated with mineral oil from a separate lubricator skid.
Due to persistent problems with the lubricated parts, the machines had already been converted to use non-lubricated wearing parts.
When originally commissioned the compressors were immediately a source of serious and regular mechanical trouble.
The Cast Iron piston rings and Piston Rod Packing rings were suffering an intolerably short lifetime as were the piston rods and cylinder liners.
The facility had kept quite good maintenance records and reports from various engineers showed that the compressors were having to have the cylinders re-lined and bored approximately every 6 weeks to 12 weeks.
This involved an outage of at least a week each time and was extremely costly in labour and parts usage.
The plant operators on this facility were also responsible for minor maintenance tasks and they were telling me that they were changing first stage suction and discharge valves on most days just to keep the machines operating.
Since the original equipment manufacturer could offer nothing of substance to improve the performance of the machines, the maintenance engineer of the plant had called in a specialist compressor parts manufacturer to see if they could advise of any improvements that could be made.
This specialist company then put forward a proposal to convert the piston rings and piston rod packings to non-lubricated operation using special self lubricating polymer materials.
This modification was duly carried out and the machines improved to the point of generally running around 3months between maintenance overhauls and around 12 months between cylinder relining.
However, the frequently occurring valve problems remained unaddressed.
Last Updated on Sunday, 28 February 2010 15:21