OPERATION OF A TWO-STAGE RECIPROCATING AIR COMPRESSOR - FAULTS

• The 2nd stage discharge pressure exceeds the relief valve setting, causing it to lift. Causes:
• A faulty/ leaking 2nd stage discharge valve (the valve does not seat, so the pressure builds up).
• A blocked/ restricted 2nd stage discharge line or the air receiver/ system back-pressure.
• Excessive moisture/ water in the air (water hammer/ pressure surge).
• A faulty/ incorrectly set relief valve.
• Overloading of the compressor (excessive demand).
• A leaking 2nd stage piston ring/ packing allowing pressure build-up.

• The valve plates (of the suction/ discharge valves) can break due to:
• Fatigue from repeated flexing/ impact (the plates open/ close at high frequency).
• Excessive lift/ impact velocity (the plate slams onto the seat/ guard).
• Material/ manufacturing defects.
• Corrosion/ erosion of the plate.
• Contamination (dirt, scale) causing the plate to jam/ impact.
• Incorrect spring tension/ valve setting.
• Water/ liquid in the air (water hammer) causing impact.

• The bursting disc (a safety device on the intercooler) punctures when the intercooler pressure exceeds the disc's rating. Causes:
• A blocked/ restricted intercooler (fouling) causing pressure build-up.
• A faulty/ leaking 1st stage discharge valve causing overpressure.
• Excessive moisture/ water in the intercooler (water hammer).
• A faulty/ incorrectly rated bursting disc.
• Overloading of the compressor.

• The compressor's capacity (air delivery) reduces over time due to:
• Wear of the piston rings/ cylinder (increased blow-by/ leakage).
• Wear/ leakage of the valves (valve plates not seating).
• Fouling of the intercooler/ aftercooler (reduced cooling, reduced density of the delivered air).
• A blocked/ dirty air filter (reduced suction).
• Leakage in the piping/ connections.
• Wear of the piston/ cylinder bore.
• A faulty/ worn unloader/ control system.