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Bellows Pumps

Operating Principle:

The bellows pump operates on the positive displacement principle. The rotation of the motor causes a crank mechanism to turn. This motion of the crank mechanism causes the bellows to compress for one half of the motor rotation, causing the pump to dispense liquid into the discharge line. During the other half of the motor rotation, the motion of the crank mechanism causes the bellows to expand, drawing liquid from the suction line into the bellows module. The pump uses two valves to control the flow of the liquid through the pump. Discharge pressure is maintained over the entire flow range of the pump.

What factors determine the flow rate of the pump?

There are three factors that determine the flow rate from a bellows pump. The bellows size affects the maximum amount of fluid dispensed per stroke of the pump. A second factor is the rotational speed of the motor. Speeding up the motor creates greater strokes in a given time period; therefore, increasing flow rates. Finally, the flow rate of all bellows pumps can be adjusted by modifying the length of the discharge stroke.

Can bellows pumps be run dry?

Yes, however, running the pump dry can cause liquid left in the pump to dry and cause possible valve misfunction.

Is there an optimal stroke length for the pump?

It is best to run the pump as close to 100% of stroke length as possible. Running the pump at less than 50% can have an adverse affect on the accuracy of the flow.

Bellows Metering Pumps Overview (PDF 120K)
Service Data Sheet (PDF 286K)

Single Bellows (PDF 152K)

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Service Data Sheet (PDF 290K)

Two Tandem (PDF 112K)
Service Data Sheet – Bel O Just (PDF 289K)
Service Data Sheet – Standard (PDF 294K)

Three Tandem (PDF 112K)
Service Data Sheet – Bel O Just (PDF 303K)
Service Data Sheet – Standard (PDF 307K)

Single Stroke (PDF 128K)
Service Data Sheet (PDF 224K)

Heavy-Duty (PDF 124K)

Dial-A-Flow^® (PDF 116K)

Part Selection Guide (PDF 236K)

Bellows Pump Accessories (PDF 120K)

Replacement Kits (PDF 200K)

OEM Options (PDF 2.6 MB)

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