TL;DR
A broken valve plate reduces cylinder efficiency and causes the cylinder to overheat. Identify the affected cylinder by temperature and plan a valve inspection at the next outage.
What you might see
- compressor capacity significantly reduced
- cylinder head temperature above normal
- abnormal knocking from the valve area
- suction and discharge pressures not at expected differential
Likely causes
Valve plate fatigue from high-cycle operation, typically above 10 million cycles
Liquid slug ingestion from condensate or lube oil carryover causing impact fracture
Corrosive process gas attack on valve metal or elastomers
Valve lift clearance incorrect from improper assembly
Required tools
- IR thermometer
- Contact stethoscope or vibration detector
- Gas detector
- LOTO kit
- Torque wrench (for valve cover bolts)
Safety first
- Compressor cylinder internals are at high process gas pressure. Follow the full depressurization and gas-free procedure before opening any cylinder head or valve cover.
- Hydrocarbon gas in the cylinder is flammable. Confirm gas-free with a detector before using tools or lights near an open cylinder.
- H2S service requires supplied-air respirator during any cylinder opening.
Procedure
- 1
Record the cylinder head temperature on all cylinders using an IR thermometer. The hot cylinder has the failed valve.[1]
- 2
Check the compressor capacity ratio by comparing the current suction and discharge pressure to the design curve.[1]
- 3
Listen to each valve cover with a contact stethoscope. A ticking or clicking sound on a specific valve cover indicates a broken or leaking plate.
Warning: High-pressure process gas is present at all valve covers. Do not loosen any valve cover bolt without first isolating, de-pressurizing, and confirming the cylinder is gas-free. - 4
Review the cylinder lube oil rate and separator drain frequency. Overlubrication can cause liquid slugging.
- 5
Plan the valve inspection. At shutdown, isolate the cylinder, vent to flare, and confirm gas-free before removing the valve cover.
- 6
Remove the valve assembly and inspect plates, seat, springs, and retainer for cracks, missing pieces, or deformation.
- 7
Replace the complete valve assembly including all plates and springs. Do not reuse damaged plates.
Sources
Ariel Corporation Ariel JGC / KBV / KBZ Reciprocating Gas Compressor general technical documentation, Ariel Corporation
Ariel JGC / KBV / KBZ reciprocating compressor general compressor valve inspection and replacement procedures (general)
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