Why does Vane pump called unbalanced pump?

The term “unbalanced” in vane pumps is derived from the unequal distribution of hydraulic forces around the rotor when it is operating. However, unlike most pump designs that have symmetrical and balanced forces, vane pumps inherently contain an asymmetry of forces because of their construction and mode of operation. Therefore, below are some of the key reasons why vane pumps are often referred to as unbalanced?

Offset Rotor: The rotor is centered around the axis in a vane pump but is set aside within the cam ring. When this rotating rotor occupies this offset position, there can be different hydraulic force acting on rotor due to inequality in chamber size.

Asymmetrical Pressure Distribution: Since volumes of these chambers vary during rotation, the produced hydraulic forces will not be distributed uniformly. As a result, one side of a rotor can have higher pressure than another does leading to imbalance in force.

Side Loading: Inequitable forces frequently cause “side loading,” where the rotor is pressed against one wall of the housing. This has two consequences; it increases frictional losses hence decreasing efficiency thus increasing wear and tear on bearings seals and other components.

Mechanical Stress: The unbalanced nature causes more mechanical stress in such pumps.Unfortunately,this may result into deformations besides reducing its reliability especially at high pressures or after long use.

Reduced Lifespan: Because of unbalanced hydraulic forces, overall life-span for pumps reduces since rotors,vanes,and other parts experience accelerated wear and tear.

Heat Generation: More heat is produced within such pumps when they are not balanced. Consequently,this could cause overheating problems which need extra measures to control thus making it a complex operational system.

Limited High-Pressure Capability : Unbalanced forces make them less suitable for high-pressure applications.Increased side-loading as well as mechanical stresses at high pressures speeds up wear out process resulting into rapid degradation or even failure at times.

Complexity in Sealing: Consequently,more complex sealing mechanisms are required to prevent leakage which further complicates the pump’s operational and maintenance procedures.

Flow Pulsation: This imbalance in hydraulic forces often leads to flow rate pulsations, which may not be suitable for applications that require a smooth, consistent flow.

Consequently,vane pumps are often referred to as unbalanced and are used mainly in low pressure applications where these effects of unbalanced forces are manageable. High pressure or high-reliability requirements can also be met by more balanced designs such as piston pumps or gear pumps.