Energy Efficient Impeller Selection

In certain industries, pump impellers have just one standard diameter for each motor size, depending on the motor chosen for a given application. This means that pump flow needs to be regulated by a valve. Forcing the flow through a constriction to achieve the correct flow rate increases friction, so energy is wasted.

Impellers on pumps already installed

Energy efficiency is far more significant to the bottom line than the capital outlay to purchase a pump. For example, an existing application requires a power input of 23 kW to satisfy the hydraulic specification. The pump installed was equipped with a 30 kW motor because a 22 kW motor would not have been sufficient. As the pump has a standard impeller designed for 30 kW, 25% of the energy required is wasted. 7 kW of waste, for instance, can consume more than €49,000 worth of electricity over a 10-year operating life. When pumps with standard impellers fail, many plant managers send them out to be repaired, although repairing a pump will not solve the problem of energy wastage. The solution is to adopt a pump management policy that gives clear guidelines on when to purchase new pumps with custom impellers.

As a rule, pumps with long running hours and those with standard impellers operating at a flow rate just above that required for a smaller motor size should be replaced. Pumps that run only occasionally and those with standard impellers nearly matching the motor size can be repaired. As this example has shown, there are times when replacement of a fully functional pump can be justified on energy grounds.

Custom impellers on new CP pumps

On average, pumps running with custom impellers are up to 10% more efficient than pumps with standard impellers because the outside impeller diameter is reduced to exactly match the specific system requirements. Customising impellers on standardised pumps is a cost-saving and effective way to cut power consumption. With its impeller trimmed to match the specified duty point, the pump will operate at its best efficiency point. Added to that, custom impellers maintain efficiency across wider load ranges and help reduce pump life cycle costs.

Custom impellers will reduce your energy costs. This is why CP offers you individually customised impeller diameters on all our pumps as standard – around the globe.