Vacuum assisted prime

Vacuum assisted priming:

As most people in the pumping industry know, pumps are not compressors and can have major difficulties when air enters the suction line or when dealing with intermittent flows. In fixed installations, these factors can be controlled and measures can be taken to avoid circumstances where air enters the suction hose. With mobile pumping equipment however, this is not the case.

There are a number of types of pumps that are capable of handling air. If we ignore the positive displacement pumps and focus on the centrifugal pumps, we find two types of pumps with self-priming capabilities:


  • Self-priming pumps (a.k.a Wet prime)
  • Auto-prime centrifugal pumps (a.k.a. Vacuum assisted centrifugal pumps, or dry prime)

The self-priming pumps have been around for ages and any pump professional has encountered them in the field somewhere. Although there is still a place for these pumps in today’s market, we have seen how the auto-prime pumps have made their way into the market.

When focusing on the BBA auto prime pumps, the BA range, we see that we are dealing with an end-suction pump that is fitted with a MP diaphragm pump and float box assembly combined with a non-return valve fitted on the discharge port.

Upon starting the engine, the MP vacuum pump creates a vacuum in the pump by removing the air. As the discharge line is sealed off by the non-return valve, this vacuum draws the fluid through the suction line into the pump casing. As soon as the pump casing is filled with water, the centrifugal pump takes over and starts discharging the fluid through the non-return valve into the discharge line. At that same moment, the float rises up thereby closing the priming system and preventing carry over of the fluid. Should the flow stop for any reason, the float will drop down again, re-starting the priming sequence.

BA Pump Cutaway

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