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Tag Archive: close loop

Manifold for motors in close loop.

Just a note about one direction motors (not reverse!) in close loop applications.

There are a lot of different ways how to proceed with a hyd. motor in close loop applications to make motor work safe and reliable. From my experience, almost each one direction motor application is required to have the next items:

  1. Anti-cavitation check valve
  2. Pressure relief valve
  3. Case flushing valve
  4. Test ports

Each motor manufacturer has own solutions for their motors, but here are problems you can meet:

  1. OEM solution usually is not flexible: you can use only what they have. If you need for example flushing of the motor case – you have to design something external anyways.
  2. Price for these options is unreasonably high;
  3. Delivery time increased on 2..6 weeks;

Here is how I like to proceed for one direction motors – with an external manifold, mounted by hoses flange botls directly to both motor ports:

Motor Flushing

  1. The manifold is designed with through “A” and “B” SAE Code 62 ports with grooves for O-Rings from both sides. Using gender changer plates (for example, solution from Inserta) the manifold can be mounted in any direction/position and ports can be easy swapped if it required.
  2. Anti-cavitation valve is integrated to pressure relief valve is a very compact cartridge, which saves space in the manifold. Like an example, here are solutions from Hydac (DBRV16P) and Rexroth (MHDBN).
  3. Flushing flow control valves examples: HYDAC (SR06-01 or SR08-01) or SUN Hydraulics FDCB-LAN. The benefit of Hydac SR valves is SAE ORB cavity: if you do not need flushing valve you can still use this universal manifold but jut plug cavity with the regular ORB port plug.
  4. And of course test ports. I like to involve as many test ports as it is possible to make easy maintenance.

The benefit of using flushing flow control valve (vs fixed orifice) is you can adjust required flow for any motor size specificly for application conditions, you do not need to pick the size and replace the orifice with each new motor.

The only thing you have to be careful about is a motor case drain pressure. Therefore, before adjusting a flow put a pressure gauge between the manifold and port “D1” and increase flow slowly to reach the required flow rate but not exceed max case pressure.

Flushing line from the manifold needs to be connected to the bottom case drain port of motor. From the top case drain port, the line needs to be plumbed directly to a tank.

SANFAB Injector

What is a wonderful gadget I met today! Will try to use it in next applications. It used for oil recirculation, but it seems like you can make a close loop system with open loop pump, and get almost all benefits of the close loop:

  • reduced tank size
  • lower weight
  • higher pump work rpm

With benefits above this device is really welcome at the mobile applications where open loop pumps need to be involved. For example, at the project I’m working now, I got a situation where the open loop pump has to work at high 2500 rpm (2100 diesel engine + PTO ratio) and by some reasons open loop pump I need to use. And it isn’t easy to find not expensive open loop pump for so hight cont. work RPM.

If it is interesting here the link for the gadget: https://www.sunfab.com/products/accessories/injector/