General Pump FAQs

1. How do pumps work?
   
   
2. Are centrifugal pumps variable speed?
   
   
3. What exactly is a positive displacement pump?
   
   
4. Which pumps can I run dry?
   
   
5. What is the maximum viscosity rating for pumps?
   
   
6. What pumps do you carry that will handle particulates?
   
   
7. I need gentle pumping action, what do you recommend?
   
   
8. When do you need to perform maintenance on pumps?
   
   

Pumps move fluid in a variety of ways:


1. Centrifugal Pumps - Use centrifugal force to push the fluid through the outlet.
   
   
2. Metering Pumps - Bellows, diaphragm, peristaltic, piston, and syringe pumps are all metering pumps that pull the fluid through the inlet valve into a chamber, close the inlet valve, and then push the fluid through the outlet valve.
   
   
3. Positive Displacement Pumps - Bellows, double-diaphragm, flexible impeller, gear, oscillating, piston, progressing cavity, rotary lobe, rotary vane, and peristaltic pumps have a fixed cavity that the fluid is pushed through by rollers, gears, or impeller. As the fluid is pushed through, it leaves a void or vacuum which pulls in more fluid.

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Most centrifugal pumps do not have variable speed motors. However, you can control flow rate on the discharge using a valve.

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A positive displacement pump emits a given volume of fluid for each revolution of the motor. Bellows, double-diaphragm, flexible impeller, gear, oscillating, piston, progressing cavity, rotary lobe, rotary vane, and peristaltic pumps are all positive displacement pumps.

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Peristaltic, piston pumps with ceramic heads, bellows pumps, and diaphragm pumps can be run dry for any length of time. Centrifugal, rotary vane, and gear pumps should not be run dry; exceptions are if the gear or impeller is made of a self-lubricating material such as RYTON in which case the pump can be run for a few minutes while priming.

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This depends on the type of pump and the specific pump. Diaphragm pumps (especially double diaphragm pumps) and gear pumps are usually the best for viscous fluids.

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Diaphragm pumps, bellows pumps and peristaltic pumps will work well. When choosing materials, consider chemical compatibility and resistance to wear. Use a pump with larger fittings so they don't clog as easily.

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A peristaltic pump, used at low speeds. You can also use a diaphragm pump, again at low speed. Centrifugal and gear pumps, which work at high speeds and have high shear rates, should be avoided.

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This depends on the pump and the application. In general, diaphragms on metering pumps last about 6 to 12 months; gears on gear pumps last about 3 to 6 months; and motors usually last for years. DC motors require periodic brush replacement. It is important to monitor brush wear; normally brushes should be replaced every 6 months.

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