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Preventing Tandem pump crosstalk

Preventing Tandem pump crosstalk

(OP)
I am looking for ideas to eliminate cross-talk in a hydraulic system with tandem pumps in parallel.
To start, I will be using two X variable displacement pumps that are HP and Load sense controlled.
The pumps will feed into a common manifold and be diverted to a multitude of valves.
The general idea is to have two independent pumps feeding the system with the ability to take one of the pumps offline while allowing the system to run at reduced flow capacity.
I have utilized tandem pumps before in a similar situation, the problem was setting up the pump controllers so the pumps didn't "Chatter" which required setting one pump controller up at 100-200PSI
below the other pump so one would be on standby until the flow demand saturated the pump, dropping the pressure and bringing the other pump online.
Both pump control signals come from the common pressure manifold.

Does anyone have any suggestions to eliminate this Chatter?

Thanks

RE: Preventing Tandem pump crosstalk

What pumps are you using? I assume this is a constant pressure system?
Use a common pressure controller for both pumps. Or is that what you did? Rexroth has a controller option called DRL for the A11VO, see RE 92500/10.09.
Check valves on the pumps P ports of course.

On another A11VO pump there is mentioned a minimumdisplacement damping, RE 92510/07.2013 page 20. I'm not sure if that would help you but I assume the chatter occurs when running with pressure and 0 flow.

Parker may have something similar for the PV series, I haven't checked.

RE: Preventing Tandem pump crosstalk

Agreed, some pumps are more susceptible to this phenomenon than others so you need to tell us which pumps you are using.

There are two schools of thought on staggering the compensator settings. Some say it's best to set them at the same pressure and even out the work load whereas others say that if you do that the chances are that both pumps will wear out at the same time. There are merits to both points of view.

RE: Preventing Tandem pump crosstalk

(OP)
Thanks for the response.
The previous application I ran into this problem was on a HPU with combined distributed flow to three large hydraulic motors. any of the three motors could handle most of the flow on their own or all three could operate a reduce flow capacity. at times, they required little to no flow.
I used the tandem Rexroth A11V0 160 setup with charge impeller and power limiting hydraulic controllers. (LRDH2) (It was coupled to a diesel engine for background) Both controllers were connected to the distributed pressure manifold.
Checks were installed on each pump outlet as well as a custom unloading/relief manifold.

I'm wondering if electronic control is a better solution to remove the chatter.

RE: Preventing Tandem pump crosstalk

Your best bet would be the DRL (parallel) control (as mentioned by Jacc) but I don't think you can combine that with the power limiter on the A11V.

When you say 'electronic control' are you talking about electronic pressure control or electronic displacement control? If it's the latter I don't think you can do that with power limiting either on the A11V, although you may be able to with the A4V.

Best to talk to Rexroth direct really.

RE: Preventing Tandem pump crosstalk

We use external proportional pressure reducing valves to directly control the pressure of our six Rexroth pump system. Admittedly not a cheap option, but we don't have interactions and we can adjust the pressure on the fly. ISZ

RE: Preventing Tandem pump crosstalk

(OP)
Thanks for everyone's input,
I will have to review my options and approach vendors for a solution.

Cheers

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