Canned Motor Pumps for the Conveying of Liquefied Gases — Alternative for High Pressure

Related Vendors

Lutz Pumpen GmbH

EDL Anlagenbau Gesellschaft mbH

ProMinent GmbH

HERMETIC-Pumpen GmbH

Energy Efficiency

Usually canned motor pumps are equipped with orifices. A Q_min orifice secures the necessary minimum flow rate for the discharge of the motor heat loss. The Q_max orifice ensures that the minimum differential pressure in the rotor compartment, which is needed to stabilise the axial hydraulic thrust balance and prevent the partial vaporisation is maintained. Moreover, this orifice prevents an interruption in the flow rate if only a minimum suction head is available. A constant flow regulator can be used as an alternative to the Q_max orifice. The constant flow regulator has been specially developed for liquefied gases to permit the safe operation of canned motor pumps in a range that is normally impossible for pumps with Q_max orifices.

This means a higher differential head and a higher flow rate with simultaneous protection against cavitation and motor overload. Often a smaller, lower priced pump can be employed or multistage pumps, which by reason of the higher degree of efficiency can be used with a lower stage. As a rule this saves 5% of the price of the pump.

Besides the saving of costs by a more energy efficient pump, the constant flow regulator also has the benefit of sustainable energy saving. The area between the pump characteristic curves with Q_max orifice and constant flow regulator represents the energy saving. As the acquisition costs for the pump represent only 5 to 10% of the life cycle costs, the energy costs, however, can amount to up to 80%; this is an additional criterion for the application of a constant flow regulator instead of a Q_max orifice.

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