Flow + Flow

[Robert128]

Hydaulic Question:
Will adding the flow from on hydraulic pump to the flow of another Hydraulic pump increase the GPM rate. Or will the pumps work against each other. - Will the pressure stay the same.
Thank You for any help on this

 

[mmurphy]

During periods of low pressure I would only imagine that it would be yes. I work in water treatment and on certain things you may have 2 pumps in series that would get you better "head" pressue. (Water column height) In parallel like you are asking you will get the flow of each pump minus the restriction , minus friction, and minus "head. At some point one pumps head will stall out other if one is not of same head pressure. I had never been around anything like in the way you are talking, but I would run them as seperate circuits before running them together. I hope to hear from the other guys on this.

 

[J_J]

Hydaulic Question:
Will adding the flow from on hydraulic pump to the flow of another Hydraulic pump increase the GPM rate. Or will the pumps work against each other. - Will the pressure stay the same.
Thank You for any help on this

I would think that if the pump are identical, that one could combine the output with a check valve on the output. If the pumps have different pressure ratings, not sure about the outcome.

http://www.engineeringtoolbox.com/pumps-parallel-serial-d_636.html

 

[AKKAMAAN]

Hydaulic Question:
Will adding the flow from on hydraulic pump to the flow of another Hydraulic pump increase the GPM rate.

YES

Or will the pumps work against each other.

I would have a check valve on each outlet line, to secure a "forward bound flow" from both pumps, if something happens with the drive of each pump....

I does not make any differens if the two pumps are of different size

- Will the pressure stay the same.

YES

Edit: This method is NOT good for some vane pumps that do not have spring loaded vanes......

 

[oldnslo]

Hydaulic Question:
Will adding the flow from on hydraulic pump to the flow of another Hydraulic pump increase the GPM rate. Or will the pumps work against each other. - Will the pressure stay the same.
Thank You for any help on this

Yes you can combine flows provided you take the precautions that otehrs have stated.

1) Have seperate relief valves for each pump located before the check valves for each pump.

2) Pressure is a result of resistance to flow so pressure will remain the same for the same load provided line sizes are appropriate. Make sure your line sizes are correct for the increase flow rate.

3) Make sure both pumps are drawing from the same reservoir.

In theory this what a hi-lo pump is for log splitters.

Roy

 

[J_J]

The question might be, if one of the pumps has say a pressure of 2200 psi, and the other one 3000 psi, and different GPM's. What will be the result? Log splitter pumps switch over from low pressure and high GPM, to high pressure and low GPM.

 

[AKKAMAAN]

The question might be, if one of the pumps has say a pressure of 2200 psi, and the other one 3000 psi, and different GPM's. What will be the result? Log splitter pumps switch over from low pressure and high GPM, to high pressure and low GPM.

Pressure will be set by the relief valve, and you do not set the pressure higher than the weakest link can handle......

And when you say "one of the pumps has say a pressure of 2200 psi, and the other one 3000 psi"... why should one pump "have" or make higher pressure than the other one, if they are mounted parallell into the same pressure line????



Oldnslo suggests a relief valve on each pump, before the check valve.....that is recommendable, but it possible to live with one RV too .....as long as the RV on the combined pressure line can handle the total flow from both pumps.....
(common industry code is to NOT have any valves between pump and RV, the check valve could break down in a way so it plugs the presssure line)

If you set individual pressure on the pumps, that means one pump can by pass while the other one keep "working"....the check valves makes this possible....but it would be big waste of energy, that will overheat the system...I would definately NOT use different pressure setting on the two or more pumps that are combined into the same system.....

 

[mmurphy]

Robert, you got some of the best advice from the guys you can find. Now like the curious little kid I am!!! Is this just hypothetical question,or a project you are thinking about?

 

[J_J]

Pressure will be set by the relief valve, and you do not set the pressure higher than the weakest link can handle......

And when you say "one of the pumps has say a pressure of 2200 psi, and the other one 3000 psi"... why should one pump "have" or make higher pressure than the other one, if they are mounted parallell into the same pressure line????



Oldnslo suggests a relief valve on each pump, before the check valve.....that is recommendable, but it possible to live with one RV too .....as long as the RV on the combined pressure line can handle the total flow from both pumps.....
(common industry code is to NOT have any valves between pump and RV, the check valve could break down in a way so it plugs the presssure line)

If you set individual pressure on the pumps, that means one pump can by pass while the other one keep "working"....the check valves makes this possible....but it would be big waste of energy, that will overheat the system...I would definately NOT use different pressure setting on the two or more pumps that are combined into the same system.....

The issue is not why two pumps have different pressures, but what if that is what you have to work with, and you want the GPM's. Just suppose you have two pumps that you want to put in parallel, and each develops a different pressure. Does anyone know the outcome. A pressure gage on the combined flow will probably show the highest pressure available.

Just had a second thought, and that is since the pressure is based on load, and the one hyd motor will develop 3000 psi, then the smaller 2200 psi pressure pump will relieve to tank, when the relief pressure is achieved.

I believe that if the load is within the pressure limits of the smaller pump, then the outputs will be additive. Any system relieving in a continuous mode, will develop a lot of heat.

 

[oldnslo]

If you set individual pressure on the pumps, that means one pump can by pass while the other one keep "working"....the check valves makes this possible....but it would be big waste of energy, that will overheat the system...I would definately NOT use different pressure setting on the two or more pumps that are combined into the same system.....

Depending on how complicated he wants to make his system he could use an unloading valve to unload the lower pressure pump using the higher pressure pump as a pilot pressure source. Makes this a glorified hi-lo system.

Pretty much anything is possible, boils down to how complicated do you want the system and how much money do you have....

Roy