Self-Priming Flexible Impeller Pump Guide

Self-Priming Flexible Impeller Pump Guide

Self-Priming Flexible Impeller Pump Guide

Self-Priming Flexible Impeller Pumps, also known as flexible vane pumps, are a form of positive displacement pump. They move fluid from the suction port to the discharge port by trapping an amount of fluid between its impeller vanes and then forcing it round towards the outlet.

The vanes of the impeller deform slightly when rotating inside the pump casing, moving the fluid from the inlet to the outlet at a steady, pulseless flow without pressure spikes. This principle combined with a gentle pumping action and a high self-priming capability, up to 6 m from dry, makes these units ideal for transfer, filling, dosing and filtration applications.

Their design enables them to handle thin and viscous (up to 50’000 cPs) fluids as well as solids in suspension (up to 25 mm). They are capable of discharges pressures up to 4 bar and flow rates up to 1200 l/min & maximum fluid temperatures up to 120ºC.

Features & Benefits

Thanks to the intrinsic simplicity and versatility of their design Self-Priming Flexible Impeller Pumps have many features and benefits which make them ideally suited to a plethora of applications.


Extremely good self-priming ability: They are capable of dry suction lifts up to 6 m from dry. Enabling the evacuation of sumps, tanks, drums & IBCs without the need for a non-return valve or manual priming on installation.



Reversible operation

 Reversible operation: Can operate bi-directionally, which allows for the return of any excess fluid & emptying of pipes at the flip of a switch located on the terminal box of the motor. This is particularly useful when emptying tanks for cleaning purposes and refilling upon completion.



Solids & Viscous Product Handling

Solids & Viscous Product Handling: Can handle soft and fragile particles in suspension as well as viscosities up to 50’000 cPs, at low operational speeds. The pump will pass the solids without causing any damage to them, air locking or emulsifying the product. This makes these pumps particularly suitable for shear sensitive products.

Solids Passage Capability:

Mini:             3 mm

Midex:          5 mm

Minor:           10 mm

Major:           15 mm

Maxi:            25 mm

Pulse-free pumping action

Pulse-free pumping action: Can be used for filling, dosing or filtration applications. The Midex and Minor ranges can be fitted with spring loaded by-passes and others fitted with manual by-passes to facilitate operation with nozzles or valves to protect against dead heading.

Pump Head can be rotated into 5 positions

Pump Head can be rotated into 5 positions: Enables installation into various pipework configurations. The motor can also be mounted above or below the pump head, thus enabling the customer to make the pump work for the system.

Pump Selection

Pump Selection

Performance curves and tables display differential head. Therefore, a calculation on the total required differential head (sum of the suction and discharge static heads and pipework friction loss) needs to be made before selecting the correct pump.

Changes in viscosity can affect the flow rate and suction lift capability of the pump. For example at 100 cPs a 25% loss can be expected and at 4000 cPs a 60% loss can be expected. The following speed brackets should be taken into consideration:

100cP:   900rpm Max

2000cP: 470rpm Max

4000cP: 300rpm Max

For pumps being used on both low and high viscosity fluids then 2 speed, mechanically variated and inverter driven pumps are available.

Pump Selection2

In order to determine the correct pump for the intended application, and once the total differential head has been calculated, you can plot your required flow rate on the performance curve to intersect with a pressure line. If this matches your required capacity you are good to go! A more detailed performance table is also available to more accurately understand the flow and pressure capability of the pump in question. Careful consideration needs to be made with regards to the voltage and speed of the pump.