pressure and flow control variable displacement pump 3

[naphty]

Hi Members
Need some tips on this subject.
If the flow controlled is opened in pressure and flow control variable displacement pump, the flow will increase due to pressure drop. How does this occur?

 

[BigInch]

System Curve resistance decreases when any valve is opened. Decreasing system resistance results in a lower required inlet pressure necessary to maintain the same flowrate. If no other control variable is changed, the pump tends to produce the same head as before the valve was opened. That trend will increase the flowrate until decreasing output head with flowrate (in the case of a centrifugal pump), or power balance (in case of a positive displacement pump) is reached and a new operation point is found. Once that new flowrate is found, you may adjust the pump's displacement until the volumetric_displacement/unit_time matches the new system flowrate.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[hydtools]

First comment: you would not have an independant flow control device if you have a flow and pressure controlled/compensated variable volume pump.
If you open the flow control, system pressure drops and the pressure feedback to the pump causes the pump displacement to increase in an attempt to increase flow and therefore system pressure to raise the pressure to the pump control pressure setting. If the required flow exceeds the pump flow control setting, then that control will limit flow and also system pressure.

Ted

 

[Oldhydroman]

Hi naphty

As your other question was about a pump with a DR controller, would I be right in thinking this question is about a pump with a DFR controller?

DOL

 

[naphty]

Hi Memebers

Yes Oldhydroman it is a DFR. By the way thanks everyone for the tips.
Have a great day.
Naphty

 

[RobertHasty]

Everybody is talking about orifice and proportional valves which limit the pump flow. I was lately in a debate with a colleague of mine. He said to me that if we use a non-proportional valve (ordinary DCV) the pump compensator will swivel and adjust it's flow to the load. Somehow this doesn't sound convincing to me. I highly doubt that the pressure drop on DCV will be sufficient enough so that pump swivels. Non proportional DCV would not make the pump to swivel because he is fully opened and by that fact the pump is delivering it's maximum flow?

 

[hydtools]

When the non-proportional directional control valve is opened, the pump will sense a drop in pressure from its near-zero flow at its holding pressure and increase flow(swivel the piston plate) to attempt to increase the load pressure up to the pump pressure control setting. The pump will cease swiveling when the flow through the load creates a pressure to match the pump control pressure setting. If the load does not create sufficient pressure back to the pump control, the pump will continue to stroke up to maximum set flow.

Ted

 

[RobertHasty]

Hy hydtools,thanks for reply.

I'm not quite sure I have understood this well. let's use for example DFR control with 4WE valve.

According to DFR control, the flow control is set at 15-20 bar (if I understand it correctly). Maximum pressure drop at 4WE valve is ~11 bar. So, according to this, there should be no swiveling of swash plate by using this 4WE valve. Correct?

 

[hydtools]

11 bar is less than 15-20 bar, so the pump swash plate will swivel to increase flow in an attempt to increase pressure to the 15-20 bar setting.

Ted