Reciprocating compressor
Also known as: piston compressor
Short definitionA compressor that compresses vapour in cylinders with pistons driven by a crankshaft. It covers a very wide range of capacities and temperatures, and the larger models can be repaired on site.
It works much like a car engine. As the piston draws back, the suction valve opens and the cylinder fills with vapour; as the piston moves forward, the vapour is compressed and leaves through the discharge valve. Models range from one cylinder to eight. Capacity is set by the number of cylinders and the speed. Small ones are hermetic, medium and large ones semi-hermetic, and those in ammonia plants are open type.
Because it runs at any evaporating temperature between −45 °C and +15 °C and with almost any refrigerant, it is a frequent choice for freezer stores and blast freezers. Stepped capacity control is possible by cylinder unloading. It is noisier and vibrates more than a scroll. Its weakest point is liquid: if liquid reaches the suction, the valves break. The superheat setting, crankcase heater and oil return must be set up correctly.