Improving ED cycles and safety on reciprocating compressors
Three North Sea floating platforms faced closure due to gas leaks on reciprocating compressors. Could PPE keep the platforms open with the correct choice of sealing material and geometry?
Problem
Two 4-cylinder and four 6-cylinder HOS reciprocating compressors, located on three floating platforms, were experiencing repeated problems with failure of OEM sourced seals due to gas leaks.
The compressors operating at 150ºC, at a pressure of 200 bar with a decompression to 12 bar in one minute would fail after just 10 cycles. The gas leaks resulted in the compressors having to be stopped, so causing explosive decompression on the valve head seals (from 3,000 revs to stop in six seconds). Each gas leak was reported to the HSE, and due to safety concerns, any future incidents would result in closure of these three rigs. To avoid these closures, a solution was required which could reach at least 30 cycles.
Solution
EnDura® V91J O-ring seals with PTFE back-up rings manufactured by PPE were fitted to provide high levels of resistance to explosive decompression. During six months in the field, the compressors have operated without a single leak occurring for over 30 cycles. On removing the EnDura® seals after use they were found to be completely intact, showing little sign of explosive decompression.
Further seal geometry development by PPE provided an L-seal with a single PTFE back-up ring, which provided even better results. The client was so impressed, they ordered a complete refit of compressors on a number of rigs. This resulted in increased efficiency and improved safety.
Result
The specification of EnDura® V91J and L-seals with PTFE back-up resulted in increased ED cycles from 10 to over 30 cycles, along with improved efficiency and safety across the assembly.
A spokesman for the compressor company said “the standard offering for ED conditions in compressors was Aflas, as it is naturally impervious to gas and offered good ED resistance. However, Aflas is not suitable in cold temperatures as it is difficult to fit into the grooves – which often resulted in gas leaks. We have been trying for years to sort this problem out. EnDura® V91J offers improvements in all areas.
The superior properties and ED resistance of EnDura® elastomers are key to the success seen in this application, characteristics that are unrivalled in the oilfield sealing industry.
The HSE were so impressed by the dramatic improvement, they issued information to all North Sea platforms, citing the case as an opportunity for improvement.
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