April 29, 2011
This case study is for a Gas Transmission Company in Colorado. The compressor is a 2-Stage Reciprocating Compressor – Ariel JGU/6 with fixed volume pockets and automatic unloaders.
- A few months after the client starting monitoring this unit on Enalysis™, with field data being provided every 6 hours through SCADA, our Enalysis™ Reports started highlighting a 17% – 25% flow discrepancy between stage 1 and 2.
- Enalysis™ Reports showed that the 1st stage was moving more gas than the 2ndstage was moving by about 17% to 25% which was not possible on this machine unless there was a leakage of some type.
- We were flagging 7-8% blowby which is just considered "Moderate". This ruled out the likelihood of damaged valves. Valve repairs that were performed did not show any effect on fixing this flow discrepancy.
- Detechtion recommended checking all automatic unloaders since this was a volumetric issue highlighted by Enalysis™. All unloaders were re-built and gaskets replaced.
- It was also found that the Solenoid that actuated the FVP in throw #3 was not working, keeping the pocket in the "open/unloaded" position. This solenoid was replaced.
- As can be seen in the graph below, both 1st and 2nd stage flows started matching much better after these hardware repairs:
- Compressor flow increased by 4.56 MMscfd after the pocket repairs. The fixed volume pockets were actually able to close all the way without any leakage.
This flow increase represents approx $547,200 per month at $4/Mscf gas.