Design of pump, prv, dir. valve to operate a double acting cylinder.

[sarakhan]

Hi all.
I have a practical question, to work with a double acting piston cylinder (1m Stroke length).
If i want to have a cylinder velocity of 0.5m/s, run by a Internal Gear pump operated with a 4/3 valve, and a prv.
1.Is having a pump displacement of 1.5e-4 m3/rev feasible ? alongwith
2. a PRV operating at Pmax= 3e+007 Pa?
3. Hence the pressure that develops in the hoses goes around 5e+7Pa ?


Are these good values practically????

I want to adjust these 1,2, 3 values to depict a real hydraulic system. The problem is if i try to make the hose pressure to be around 3 e7 pa then I have to operate prv at 1e7 pa and then the pump displacement goes really high. (4e-4 m3/rev to achieve 0.5 m/s ) and I cant calculate/design the hoses drops as no equation is available. Peter here suggests to use some equation for calculating pressure drops but i cant find any relevant scientific papers on it. Please suggest ....

Regards,
Sara.

 

[zeusfaber]

A diagram would be helpful. Are you just using the PRV to limit system pressure when the ram hits the end stops (and maybe using an open-centre DCV to absorb the pump flow when the valve is closed), or are you relying in the PRV for both jobs?

150 cc/rev is a pretty big gear pump (something like a size 6 Bucher pump) - and though I've seen these running into 300 bar reliefs, the fluid warms through pretty fast when you do.

A

 

[sarakhan]

The piston velocity is 0.5m/s
I cant really have a high pump displacement Im sure of that, now i have to adjust the prv and hose pressures.

 

[zeusfaber]

Once you get up to that sort of scale, you would normally see an altogether more intelligent collection of valves. Although this adds apparent complexity, it allows you better control over the pressures in the system and lets you choose a more realistic pump size.

I'll attach a simplified schematic of a real system of roughly similar scale I was working on recently:

The compensating valve is set to no more than size or seven bar, and unloads the pump when you don't need full working pressure,

When you load the system up, pressure from the shuttle valve stops off the compensator, allowing the pump to develop full pressure

When you hit the stops, the Main Line Relief limits the pressure to 200-300 bar.

The counterbalance valve stops the load running away from you when you try to let it down (your system will struggle with this)

You can ignore the POCV, which isn't necessary in your example application.

A.

 

[sarakhan]

SO you suggest me to add some valves to my systems? Thats something new... Well what do you think about the values I have mentioned here. Are they realistic?

 

[vpl]

Sara

Is this a school assignment?

Patricia Lougheed

******

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.