FIELD TROUBLESHOOTING CHECKLIST FOR WELLHEAD COMPRESSORS
1. Check interstage line temperatures to determine which valves have been removed from a cylinder.
2. Remove disabled valves, cages, and valves in ends taken out of service and replace with gaskets. This reduces parasitic pressure loss.
3. By-pass crank-end when not in use through fuel gas lines. Saves horsepower.
4. Is engine exhaust temperature at least 600°F? Lower temperature indicates inadequate compressor utilization.’
5. Is engine “missing” more than ten times a minute? This also indicates inadequate engine utilization.
6. Can a dual acting machine operating on crank-end be changed to head-end?
7. Can a dual acting machine operating on head-end have the cylinder clearance reduced?
8. Can a dual acting machine operating on head-end be switched to dual acting without exceeding rod loading, maximum exhaust temperature or maximum horsepower?
9. Can tandem machine operating on crank-end be switched to head-end?
10. Is a tandem machine, operating on head-end, limited by maximum rod load and/or discharge temperature? If so, correct by going to tandem operation.
11. Are there any bad valves indicated by hot valve caps (suction valves can easily be identified as bad).
12. When switching to tandem, do not maximize gas production first day. Compressor will have a tendency to trip-off due to high discharge temperature.
13. When operating a compressor in tandem, the crank-end discharge temperature can be reduced at constant suction pressure and flow by closing the head-end clearance pocket and slowing down the machine. However, this is a small effect.
14. Opening a clearance pocket to reduce discharge temperature will immediately raise the discharge temperature! However, once the wellhead pressure rises due to less gas being moved, the discharge temperature will drop.
15. For wells served by a three-phase separator, adjust the threephase separator pressure down when going to tandem operation. When the compressor suction falls below 65 PSIG, liquid will carry-over from the high pressure separator and trip the compressor unless the 3-phase separator pressure is reduced.
16. About one out of three wells will start making water “hits” when the compressor suction is dropped significantly. Usually the high pressure separator will not be able to drain sufficiently fast for the first hour. It needs to be drained manually for this period. Such wells will double or triple their gas flow after making the water hits.
17. Some wells, after making water hits exhibit an increasing wellhead pressure. This may trip off the compressor due to overload.
18. Is compressor at maximum rpm?
19. Some engines bog down below rated horsepower due to inadequate fuel gas flow.
20. Check liquid dumps for leakage (i.e. dump line is cool).
21. Is compressor suction pressure not less than 20 psi below wellhead pressure?
22. Is discharge to suction bypass check valve leaking and/or blocked-in?
23. Does metered flow match the flow predicted by curve charts? About 20% of the time they do not match. Indicates bad valves in cylinders or wrong meter reading.
24. For compressor’s with meters on suction, is the engine fuel gas flow being deducted from royalty payments.
25. Is fuel gas from the suction of the compressor? On average, a compressor will use 2% — 5% of it’s production for fuel. For tandem machines operating at maximum this can be a much higher percentage.
26. Is a well soap-sticked and flowed back properly?
27. Remember that the discharge temperature from a compressor will increase as the well pressure is depleted.
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