Compressor Failure Library

Understanding Compressor Failures

Compressors — whether reciprocating, screw, or centrifugal — have distinct failure modes. Many failures are preventable through proper maintenance of lubrication, cooling, and filtration systems.

Valve Failure (Reciprocating)

In reciprocating compressors, suction and discharge valves open and close thousands of times per minute. They are the most common failure point.

• Symptoms: Reduced compression ratio, increased discharge temperature, unusual valve sounds (clicking or hissing), and reduced capacity.
• Root causes: Fatigue from cyclic loading, impact damage from liquid or foreign particles, carbon deposits from oil carryover, corrosion, and spring failure.
• Prevention: Maintain suction filtration to prevent particle ingress, prevent liquid carryover (install knock-out drums), use correct valve material for the gas, replace valves on a preventive schedule, and maintain correct lubrication to prevent carbon deposits.

Bearing Wear

Compressor bearings carry high radial and thrust loads. They fail from inadequate lubrication, contamination, overload, or misalignment.

• Symptoms: Increasing vibration, rising oil temperature, metallic particles in oil analysis, and eventual seizure.
• Root causes: Inadequate lubrication (low oil level, wrong oil viscosity, oil degradation), contamination (dirt, water, wear metals), overload (from surging or high discharge pressure), and misalignment in coupled compressors.
• Prevention: Maintain oil quality (regular oil analysis, scheduled oil changes), maintain oil filtration, monitor bearing temperatures, prevent surge (install anti-surge control), and verify alignment.

Oil Degradation

Compressor oil degrades through oxidation, contamination, and thermal stress. Degraded oil causes bearing failure, deposits, and corrosion.

• Symptoms: Dark or discoloured oil, acidic smell, increased oil temperature, deposits on valves and bearings, and reduced oil life.
• Root causes: Oxidation (high temperature and oxygen), contamination (air, water, process gas), wrong oil type for the application, and extended oil service life.
• Prevention: Use synthetic oils for high-temperature service, maintain oil coolers to keep oil temperature below the degradation threshold, change oil on schedule based on oil analysis, and prevent contamination by maintaining seals and breathers.

Overheating

Compressor overheating damages oil, valves, bearings, and seals. It is caused by inadequate cooling, high compression ratio, or insufficient gas flow.

• Symptoms: High discharge temperature (above 150°C for most compressors), high oil temperature, tripped thermal protection, and discoloration of components.
• Root causes: Inadequate cooling (cooler fouled, cooling water flow insufficient, ambient temperature too high), high compression ratio (discharge pressure too high or suction pressure too low), insufficient gas flow (starvation), and worn valves or piston rings.
• Prevention: Maintain coolers (clean fouling, verify cooling water flow), monitor compression ratio and keep within design, ensure adequate suction gas supply, and maintain valves and rings.

Surge (Centrifugal Compressors)

Surge is a violent flow oscillation that occurs when a centrifugal compressor's flow drops below a minimum. It can destroy the compressor in seconds.

• Symptoms: Loud booming sound, violent vibration, rapid fluctuation of discharge pressure and flow, motor current swings, and potential mechanical damage.
• Root causes: Flow below the surge line (caused by downstream blockage, suction throttling, or excessive discharge pressure), insufficient anti-surge control system response, and abrupt process changes.
• Prevention: Install and maintain a reliable anti-surge control system that recycles gas to maintain minimum flow, avoid rapid process changes, keep discharge pressure within design, and test the anti-surge system regularly.