Spun Out: Is It Time for A Pump Revolution in the Chemical Industry?

Related Vendors

Lutz Pumpen GmbH

Italvacuum, Srl

ProMinent GmbH

DeanHouston Inc

Specifically, centrifugal pumps work best when they are operated at their Best Efficiency Point (BEP). Unfortunately, that is rarely realized for an extended period of time, which results in flow rates that can fluctuate constantly. Also, when a centrifugal pump operates to the left of its BEP, radial loads increase due to the way the pump generates pressure by reducing the fluid velocity. This method of operation increases shaft deflection at the seal faces, which results in increased seal wear and a decrease in life expectancy.

Working left of the curve will also increase axial loads that can overload the thrust bearings, especially in open-impeller and diffuser-type multi-stage pumps. Finally, as a centrifugal pump operates close to the zero-flow point (zero efficiency), heat will be generated at levels that can be harmful to heat-sensitive chemicals or products, which can also adversely affect safety and the quality of the resulting product.

AODDs Can Do More

By comparison, the fluid-delivery curve for an AODD pump is similar to that of the centrifugal unit, without the negative behavior that occurs when running off the BEP. The AODD pump will perform based on the inlet air pressure supplied to the pump and the system pressure it encounters.

If adequate suction pressure is available, fluid will flow into the pump and be discharged based on the relationship between the air pressure operating the pump and the system pressure.

A Real Alternative

The larger this pressure differential, the faster the pump, and when the differential is reduced, the pump’s operation will slow. This is referred to as “infinitely variable speed operation.” If the system pressure increases unexpectedly, the pump will operate until the inlet air and system pressure are equal, when it will stop — in what is termed a “deadhead” condition — with no equipment damage.

The system remains pressurized, but without differential pressure to drive the fluid. The pump will restart once the system pressure falls below the operating air pressure, which is particularly important in batch processes. In contrast, a closed valve can wreak havoc on a centrifugal pump, and with different positive displacement pump technologies operating against a closed valve can cause damage or destroy a system by reaching the burst pressure of the plumbing in very short order.

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