Two Stage Hollow Valve Rod Pump
    This pump has become the most popular pump design invented by Harbison-Fischer. It is a rugged pump which overcomes most gas locking conditions and has the ability to produce a moderate quantity of sand or other particulates. The secret to the success of the Two Stage Hollow Valve Rod Pump is its modified upper compression chamber.

    At the beginning of the downstroke, the upper traveling valve on top of the pull tube holds back the hydrostatic head and allows the lower traveling valve to open without the need to compress the fluid/gas mixture to a high pressure. As the downstroke continues, the fluid/gas mixture from the lower compression chamber moves through the plunger to the upper compression chamber.

    At the start of the upstroke, the lower traveling valve closes and the standing valve opens to admit new fluid to the lower compression chamber. During the upstroke, the fluid/gas mixture in the upper compression chamber is compressed to a higher pressure until the top traveling valve opens and allows the fluid to be discharged into the tubing above the pump completing the pumping cycle.

    The valve rod guide has a generous clearance to allow sand and other particulates to be flushed from the upper compression chamber during the upstroke. This characteristic gives the Two Stage Hollow Valve Rod Pump its versatility in gas locking applications which also produce sand or other particulates.

    The Two Stage Hollow Valve Rod Pump is available in a wide variety of materials, surface treatments and configurations. The configurations use mainly stock parts to create this special pump.