Rotary compressor: rolling piston and vane
This page uses rotary for rolling-piston and vane compressors. Both are positive-displacement mechanisms, but their moving parts and chamber boundaries differ.
Guide
ContentsRolling-piston construction
An eccentric shaft moves a roller within a cylinder. A separating vane follows the roller and divides the suction and compression spaces. Rotation changes their volume and pushes compressed gas toward the discharge. Two-cylinder designs repeat the mechanism; two cylinders do not necessarily mean two successive compression stages.
Vane construction
In a sliding-vane compressor, vanes move in slots in an eccentric rotor and bound gas spaces against the housing. These spaces decrease in volume toward discharge. This is mechanically different from a rolling piston with a separating vane, even though both constructions may be labelled rotary.
Air conditioning and variable speed
Hermetic rolling-piston compressors are used in air-conditioning and heat-pump equipment. Fixed-speed and variable-speed versions require their own motors, supply arrangements and controls. The word rotary does not establish whether a compressor can be connected directly to the mains or requires a particular inverter.
Data needed for replacement
Match the complete model code, refrigerant and oil, electrical and drive characteristics, mounting orientation, connections and performance envelope. External shell similarity is not a reliable identity check. Supported handling of liquid or oil is model-specific and must not be inferred from the rotary label.
Prepare a compressor request
Pressure conversion and pressure-ratio calculation · model selection unavailable
The pressure tool converts the supplied values and calculates the absolute discharge-to-suction pressure ratio. The request form records other requirements. Neither function selects a compressor, calculates capacity or confirms a refrigerant cycle, diagnosis or interchangeability.
For a technical review, identify the exact model and refrigerant, duty and rating conditions, electrical supply and control, oil, dimensions/connections, and the reason for replacement or service. Missing information remains unknown.
Selection / replacement · Service
Page context: Rotary compressor: rolling piston and vane
Reading another page does not change your selected topic. The topic is not a selected equipment model.
Absolute pressures and pressure ratio
Use suction and discharge pressures for the same stated operating condition and compatible measurement definitions. This is a pressure calculation; it does not check whether a compressor can operate at those pressures.
Method: 1 bar = 100 kPa; 1 MPa = 1000 kPa. Convert each input to kPa. For gauge pressure, p(abs) = p(gauge) + p(atm). For absolute pressure, use the entered value directly. r = p(discharge, abs) / p(suction, abs); r has no unit.
Both absolute pressures must be positive. Enter a positive absolute atmospheric pressure whenever either input is gauge. A negative gauge reading is allowed if its absolute pressure remains positive. Atmosphere is never assumed.
Example: suction 2 bar absolute and discharge 8 bar absolute give 200 kPa, 800 kPa and r = 4. The same result follows from 1 bar gauge and 7 bar gauge with an explicitly supplied atmosphere of 1 bar absolute.
The calculation does not provide cooling capacity, power, discharge temperature, an operating envelope, refrigerant/oil compatibility, diagnosis or a replacement model. Pressure sources, measurement uncertainty, operating stability and model limits remain unverified. Displayed results are rounded; extreme values outside finite numeric precision are rejected.