VVR & hydraulic system fill/bleed procedure

Filling up a network using the VVR should only take about 20-25 minutes the first time the system is used to allow for the addition of new oil and bleeding off air pockets. When changing fittings, hoses or filters, it should take less time as only the air bleeding would likely be required and minor fill to compensate for filter housing volume.


The following procedures are recommendations for optimum results

  1. The VVR should be installed near the pump inlet. Piping & VVR orientation to optimize air collection. i.e. forcing air return to escape inside the VVR for later bleeding.
  2. Fill system at the return line using a manual or electric pump equipped with a filter (strongly recommended).
  3. Filling must be done with all actuators in retracted position.
  4. Monitor the filling and VVR level. Fluid and air pocket will appear through the VVR top cover.
  5. Open the VVR top bleed valve (bleed tube end into a fluid container).
  6. The air pocket should disappear since the bleed valve is opened*.
  7. When the air pocket is dissipated (fluid only) and the VVR level is at 75%, stop the filling and close the VVR top bleed valve (see note 2).
  8. Start the main pump drive system. Monitor the VVR level and activate one directional valve. At this point the system network will partially be filled with fluid thus making the VVR level to go down. Most of the network returning air pockets will gather on top of the VVR*.
  9. If the VVR oil level reaches ≤ 25%, stop the drive system.
  10. Refill the VVR to 75% level and open the top air bleed valve until fluid only appears through the VVR top cover.
  11. Close the bleed valve and restart the drive system. Operate the directional valve in both directions and monitor the VVR level (Do not allow the VVR level to go under 20-25 %).
  12. If needed, refill the VVR to 75% and bleed any air pockets.
  13. Operate your equipment and after 15-20 minutes, check if any air pockets have returned to the VVR. If it's the case simply rebleed the system one last time.

* Some residual air may collect inside the VVR. Bleed if necessary.

Note 1: The remaining 25% level is used for thermal fluid compensation.

Note 2: If differential cylinders are used, they should be in a retracted position before filling the VVR.

This video shows the bleed procedure for our VVR, it's the system first oil fill and commissioning.

Fill procedure using a conventional
hydraulic unit

This procedure allows for easy bleeding and VVR fill. The proposed procedure is very similar to the way aircraft hydraulic network are bled and bootstrap reservoir are filled.

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VVR bleeding procedure

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