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Hydraulics problem

Hydraulics problem

Hydraulics problem

Hello all, i have a problem i hope you can help me with ...

My hydraulics is basic at best and have been asked how we can control a 0-80 lpm pump when we only have the output of a NG6 proportional valve (0-40 lpm) valve to do it

We have access to system pressure (200 Bar/150 Lpm max) so what i really want is to use variable / proportional pressure to give proportional access to the system pressure/flow

Is this feasible? Is there a valve out there just waiting for me to purchase it? In my mind i see the proportional pressure driving like a spring return piston which is in turn giving access to "full fat" flow

Much thanks in advance

PS If there is a go to resource for all things hydraulic i'd very much like to hear about it ! afro

RE: Hydraulics problem

What do you want to control? Pressure? Flow? Both? Why? Is the pump a variable displacement pump? Does it have built-in controls? Is this in an existing system?


RE: Hydraulics problem

Hi ted

Good points and i apologize for not having these details in the post

The output will drive a reciprocating piston pump (dynaset 520 which is more commonly used as a pressure washer)

We are using the pump to perform pressure tests so it is beneficial to drive the reciprocating pump at its maximum flow until the test pressure is reached



RE: Hydraulics problem

I'm still not sure exactly what you are trying to accomplish.

Quote (Geoff GBeard)

hydraulics is basic at best
makes it hard to post an understandable question.

Quote (Geoff GBeard)

0-80 lpm pump
does this assume you have a 0-80 lpm variable displacement pump? If so does it have a pressure compensator with an "LS" input line on the compensator?

Here is a link to the Dynaset 520
Here is a summary of the specs

RE: Hydraulics problem

Hi Akkaman

I apologize for my lack of hydraulics background and appreciate your patience

So the equipment that we supply will have a pressure and tank supply from a host piece of kit (a triton xlx) which is in effect a subsea HPU. This pressure and tank is fed into out valve pack (solenoid valves on a gallery) but they are NG6 with a max flow capacity of 40 Lpm but as you can see from the dynaset spec it can take 85 lpm.

So my question is can this NG6 proportional pressure/flow valve be used to drive a valve with a higher flow capacity to draw the 85 lpm the dynaset needs

Thanks guys!

RE: Hydraulics problem

"Solenoid valves", does that mean there is more than one?
Pushing more than 40 lpm through the valve will significantly increase pressure losses. If you need the max "250 bar" at the Dynaset 520, you might need a 300-350+ bar" pump pressure to keep up delivering the 80 lpm to The Dynaset 520.

Can't you run 2x40=80 lpm NG6 in parallel? Or is the valve manifold a flow limitation by itself?

RE: Hydraulics problem

Yes the valve manifold is a flow

And Yes , there are 6 solenoid valves and one proportional valve, the proportional valve was meant to have enough flow to drive our pump then the dynaset was introduced and we are very much stuck with the NG6 proportional valve (it lives in a pressure compensated housing due to the external pressure).

Which leaves me trying to use the same (and only) NG6 proportional valve to control the flow to he dynaset ! That's the frustrating thing , there is up to 200 lpm available but how to control it ?!

I feel like we re about have a breakthrough moment or i m about to be told i'm screwed bigsmile

RE: Hydraulics problem

Do you need the 30 lpm water flow?


RE: Hydraulics problem

I believe the flow rating of the valve is at 100 psi, 7 bar, pressure drop across the valve. More flow would be at higher pressure drop across the valve. Run the test, see what you get. The valve flow rating does not mean you cannot push more flow through it.


RE: Hydraulics problem

Hi Ted

We are stuck with the pressure as it is set by the HPU which is not manufactured or set by us, its is 200 Bar

So we have to find a way of opening up more flow to our product

Thanks !

RE: Hydraulics problem

We did actually do a test to see what max flow we can get from the proportional valve , it was 42 Lpm fully open and we are looking for 85 :(

RE: Hydraulics problem

Hi Geoff,

I'm guessing you're dealing with Perry ROV system?

Quote (Geoff)

So my question is can this NG6 proportional pressure/flow valve be used to drive a valve with a higher flow capacity to draw the 85 lpm the dynaset needs
if your inlet only 40LPM, there is no way you can get the optimum speed of the pump which need 85 LPM.
you can still run the pump with the inlet pressure of 200Bar and 40LPM but the speed will be less than half i guess.

i don't know how is the configuration of your NG6 but what i can tell from Wanfluh catalogue, i found out that the M33x2 Proportional 2-way flow control valve (QNP PM33-80)
has a flow rate of 80LPM and you can use NG10 for it.

you said you have 6 other solenoids? why don't you use them and add the proportional control after that?
is there enough to get 85LPM from those 6 solenoids?


RE: Hydraulics problem

This is a classic case whereby a simply drawn diagram would have made it much easier for everyone to figure out what was going on.

I was completely stumped as to what fed what and what the purpose is.

As I now understand it and please correct me or draw your own diagam,

You have a 200 bar / 150l/min HPU
This feeds a rack of 6 solenoid valves ( presumably on/off?) of unknown size or flowrate plus one proportioing valve which I can only assume is controlled by means of a 4-20A signal or simalar?

This proportioning valve, lets call it PV1, has a max flow when fully open of 42l/min

The hydraulic fluid from PV1 feeds a hydrualic motor with a 0-80 l/min flow capacity. The hydraulic motor is coupled to a pump which can produce up to 520 bar?

This pump is used to pressurise pipiing and the slower rate means it's taking longer to pressurise it than if you could run at 80l/min.

So why don't you couple up one fo your solenoid pumps via a fixed control valve so that at you 200 bar, you get 80l/min. As you get close to your presusre limit then turn it off and start to use the PV1.

Or make the second one 40l/min and run PV1 flat out then when you turn the second "booster" supply on it won't stop dead.

you've discovered you can't get more than 42 l/min from your valve.

Or buy a proportioning valve which can supply 80l/min.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Hydraulics problem

Hi R.Efendy

Inlet can be up to 200 Lpm but the max out put of the NG6 has been tested an is 42 lpm

We cannot change the valve gallery / manifold for a NG10

I feel like if i just knew the correct valve terminology my googling would give much better results. When i think a bout a spool valve block with a manual handle your hand is varying the flow giving access to full main system flow , now if you change that handle for a hydraulic input with varying pressure we have a winner !

It is a perry system which is my background but i have an electrical / electronic background . Hence why i just know basics and no proper terminology ! The electrical equivalent for what i m after would be a transistor bigsmile

Thanks for your response dude

RE: Hydraulics problem

Hi LittleInch

You are 99% correct and thank you fr bearing with me to understand. The 1% is that its not driving a motor, its driving a reciprocating piston pump (dynaset 520 above)

You are also exactly where i am with my thinking, a higher capacity pilot operated valve

But the proportional valve is proportional flow AND proportional pressure so what i was hoping for was to use the proportional pressure to vary the flow as opposed to a "binary" output from the the pilot operated valve

I have a number of little sketches i would have posted if i thought they would have made sense to you my learned friends!

However and again , thanks for your patience , i hope to be of some use on this forum if i see a post that's more my background 2thumbsup

RE: Hydraulics problem

Good - it's a small point but infact the pump is actually comprised of a hydraulic motor and a pump in one body. The data sheet states the discharge side and the hydraulic input side. The issue being is that I initially thought you had an electrically driven hydraulic pump, not a hydraulically driven water pump.

Also "NG6 proportional valve" doesn't give us a lot of info.

Can you list manufacturer and type or post the datasheet for the valve you actually have please. without seeing it it's not really possible to see what the valve does, but if it is a simple control valve then yes it will change flow and pressure as the two are directly linked to each other.

I'm pretty sure you can find a valve which accepts a hydraulic input to vary flow if that's what you want.

Like I said - a simple diagram would help.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Hydraulics problem

Yes, a hydraulic diagram may help.


RE: Hydraulics problem


Not fully sure what the schematic looks like, but if you call the tech people at Sun they can tell what valve you may need. If you think you know what you want it to do. They have lots of press control valves.


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