Compressor types, lubrication, capacity, and fault reasoning
Relate the machine to its mechanism
A reciprocating compressor traps vapour and reduces its volume, while a centrifugal machine adds energy dynamically through an impeller and pressure-recovery passages. A screw machine uses its rotor geometry and may have oil injection and internal capacity controls. These differences affect operating limits, unloading behavior, and likely faults. Do not transfer a valve lineup or restart sequence from one design to another. Use the actual manufacturer's instructions and the plant procedure, including lubrication, cooling, and protective permissives.
Protect the intended vapour path
A vapour compressor is not a liquid pump. Liquid carryover can produce abnormal mechanical loads, while refrigerant dissolved in oil can disturb lubrication when it boils out during startup. Accumulators, separators, heaters, and return arrangements each have specific functions. An oil separator does not remove every contaminant, and a crankcase heater is not a substitute for an oil pump. Evaluate net oil pressure using the relevant opposing pressure rather than trusting a high gallery reading alone. A low-oil trip needs diagnosis before restart, not repeated resetting.
Match capacity to conditions
Displacement volume does not equal mass flow until suction density and volumetric performance are considered. Clearance gas in a reciprocating cylinder can reduce fresh intake through re-expansion. Unloading and variable capacity can reduce output without a perfectly proportional power reduction. In centrifugal machines, the stable flow range and required lift matter; surge is not a normal condition to ignore. Parallel machines require coordinated staging, oil management, and protection. A command to run is not proof that the operating point is appropriate.
Diagnose patterns, not one reading
High discharge temperature can reflect compression ratio, suction condition, cooling provisions, or other causes. Low suction pressure is not a unique diagnosis of low charge. Compare pressures, temperatures, load, control state, and credible instrument readings before changing the inventory. Motor overloads, voltage imbalance, vibration, and bearing trends also require context. A chart of similar-load readings can reveal developing deterioration better than an isolated value. Preserve actual observations and use competent maintenance support when the work exceeds operating authority. Good operator reasoning separates symptoms, possible causes, confirming checks, and the conditions required for a controlled return to service.