Why reciprocating compressor valves fail

Reciprocating compressor valves usually fail for one of six reasons: liquids in the gas, dirt and debris, a valve that no longer suits the operating conditions, deposits, too much lubrication, or simple wear at the end of their life. The damage on the failed valve usually tells you which one, and fixing the cause matters as much as replacing the valve.

Valves are one of the most frequent causes of unplanned compressor shutdowns. They open and close on every revolution, more than 500 million times a year on a unit running at 1,000 rpm, in gas that is rarely perfectly clean.

The six common causes

1. Liquids in the gas

Liquid slugs or condensing liquids hit the plates, rings or poppets much harder than gas. Typical damage: broken plates, cracked rings, damaged seats. Check the suction scrubbers and level controls, and whether the suction temperature stays safely above the gas dew point, including in cold weather.

2. Dirt and debris

Pipe scale, sand, corrosion products, weld slag or debris left after maintenance wear the sealing surfaces and can jam the moving elements. Typical damage: scored seats and guards, embedded particles. Check suction strainers, especially after new piping or a turnaround.

3. A valve that no longer suits the operating conditions

Valves are designed for a range of speed, pressure ratio, gas composition and lift. When a field declines or a unit is moved to a new service, the valve may end up working outside that range. Typical damage: impact wear on the guard and seat, fatigue cracks. A valve redesign for the new conditions can fix repeat failures.

4. Fouling and deposits

Polymers, salts, sulphur compounds or degraded oil can build up and make the elements stick, open late or not seal. Typical damage: sticky, coated elements, leakage.

5. Over-lubrication

Too much cylinder oil causes sticking and makes the moving elements hit harder. Typical damage: oil-wet valves with impact marks. Check the lube rate against the manufacturer’s recommendation for your pressure and gas.

6. Normal wear

Even in ideal service, springs, plates and rings wear out. Regular valve maintenance on condition or at fixed intervals prevents a worn valve from becoming a broken one.

Warning signs of a failing valve

• Higher discharge temperature on one cylinder end
• Valve cover noticeably hotter than the others on the same cylinder
• Loss of capacity, or changes in interstage pressure on multistage units
• Unusual noise, knocking or vibration
• Changes in the pressure-volume (PV) trace, if you use an analyzer

What to send with a replacement request

• Compressor manufacturer, frame model and serial number (a nameplate photo is ideal)
• Cylinder bore and class, or the cylinder serial number
• The valve part number, or any number stamped on the valve
• Suction and discharge pressure and temperature, speed and gas composition, especially if conditions have changed
• A photo of the failed valve: the damage pattern helps identify the cause
• How many valves fail and how often: a repeat failure points to a cause, not a bad part

Repair, replace or redesign?

• Repair (recondition): fine for valves with worn wear parts and sound seats and guards.
• Replace like for like: right when the valve has simply worn out in the right service.
• Redesign: worth considering when the same valve keeps failing early. Different materials, lift or springs for the actual conditions can extend valve life considerably.

Send the nameplate photo and your operating conditions on the quote form. We state on every line whether a part is OEM genuine or a qualified equivalent. See also compressor packing and rider bands.

CHR is an independent supplier and is not an authorized dealer of the manufacturers named.

Frequently asked questions

How long should compressor valves last?

It depends heavily on the service. In clean, dry gas at moderate speed, valves can run for years. In wet, dirty or high-ratio service they may need attention every few months. If your valves fail much more often than in similar units, look for a cause.

Can I use non-OEM valves?

Yes, qualified equivalent valves and valve parts are available for most common compressors. See OEM genuine vs qualified equivalent parts for the questions to ask.

What material should the valve plates be?

Non-metallic plates (for example PEEK or other engineered plastics) are common because they are tolerant of debris and quiet. Metallic plates suit some high-temperature or high-pressure services. The right choice depends on gas, pressure, temperature and speed.