Priming a Dynex checkball pump when flooded suction is NOT available.

Sometimes, a hydraulic power unit is laid out in such a design that the pump and electrical motor must be mounted on top of the reservoir. In the case of a Dynex checkball pump, this is not the most advantageous situation for the pump. A checkball pump has a lot of great attributes, but one of its limiting performance factors is the ability to pull a vacuum.

When this happens, customers sometimes try different methods to prime and plumb the checkball pumps. This article will share some of our experience and provide a proven method used by our system builders.

When the above scenarios occur, Dynex mounts the pump with the inlet still facing upward or at the “12 o’clock” position. In many cases this is the highest point in the pump, so we want any air to have the easiest path to escape.

The next step is to plumb in a “Suction J line”. This is done by installing a 6” run of tubing or pipe. This is installed vertically up from the pump housing. This will allow for a column of oil to be available when the pump starts.

At the highest point of the “Suction J line”, we install a tee fitting with the topmost port capped with a plug. After that, we extend horizontally from the tee fitting away from the pump, and then finally down into the reservoir. You could add a piece of hose here for this as well (designer’s choice).

Once all fittings are tight and ready for start-up, follow the next steps to bleed any air and prime the pump:

  1. Remove the plug at the top of the tee fitting and use this to fill the pump housing with oil. You will see air bubbles start to push past the oil being filled into the pump and inlet hose.
  2. Re-install the plug and make sure it is tight to ensure no entrained air would enter the inlet plumbing.
  3. Turn on the pump for about 15-20 seconds. This “burping” of the pump will help push any residual air through the pump and allow you to determine if you need to open the plug at the top of the pump to remove any additional trapped air.
  4.  Additionally, you want to make sure the outlet of the pump is either fed directly back to tank with no restriction, or that the pressure controls are at their lowest possible setting.
  5. Repeat the above steps 1-3 as needed until you feel that the pump is fully primed.

This provides a functional method to install and use a Dynex checkball pump when flooded suction is NOT a viable option.

If you are unsure of the installation best practice or are interested in a power unit option from our team, please contact us and we would be happy to assist.

For more information visit our Power Units page, or feel free to contact us.

Tip Ninja

Applying his legendary skills toward answering tough questions, defeating difficult hydraulic related problems, and sharing his vast knowledge of Dynex hydraulic products with the world.