The shaft coupling is the connecting element between the electric motor and the pump hydraulic system. Slip-free shaft couplings employed in centrifugal pumps are divided into rigid and flexible shaft couplings.
Rigid shaft coupling
Rigid shaft couplings are mainly used to connect perfectly aligned shafts. The slightest misalignment results in considerable extra stress on shaft couplings and adjoining shaft ends.
Examples of rigid shaft coupling types
- Sleeve coupling
- Muff coupling
- Serrated (splined) coupling
- Split muff coupling (DIN 115)
- Disc coupling
- Flange coupling
- Gear coupling
Flexible shaft coupling
Shaft couplings to DIN 7400 are resilient (flexible), slip-free connecting elements fitted between driving and driven components, capable of partially compensating axial, radial and angular misalignment and shock loads.
See Fig. 1 Shaft coupling
Flexibility is usually achieved by the deformation of dampening, rubber or metal-elastic spring elements; their service life is heavily dependent on the extent to which misalignment has to be compensated. Different flexible shaft coupling designs are available.
See Fig. 2 Shaft coupling
If shaft misalignment occurs between the driver and the pump as a result of, for example, temperature fluctuations in the fluid handled (on heat transfer and hot water pumps), the double-cardanic coupling type design is often employed.
See Fig. 3 Shaft coupling
Fig.3 Shaft coupling: Double-cardanic coupling for compensating shaft offset