How Can I regulate pressure in reciprocating pump

[jor1492]

Hello all,
I have a reciprocating pump with a discharge pressure of 4400 psi and I want to regulate that to 3000 psi without losing the fluid in the line. That is because the final destinantion can not hold on that pressure level.
How Can I do that?

Thanks in advance.

 

[Compositepro]

Tell us more about the pump. How is it now limited to 4400 psi? The simple answer to your question is change the 4400 to 3000.

 

[hydtools]

I would say you will have to accept less flow to reduce the need for 4400psi required to push the current flow through your system demand.

Ted

 

[georgeverghese]

Maybe install a backpressure- recycle valve on the pump discharge set at 3000psi? With a recip pump, sensed pressure for the PCV will have to be damped to cancel out pulsations - a dampener will help. The recycle valve should return excess pressure back to source tank or vessel.

 

[LittleInch]

Don't know what you mean by losing the fluid in the line?

Just set a pressure regulator to feed back to pump inlet or source tank.

Reciprocation pumps are essentially constant volume flow pumps. What are you using this for?

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

 

[jor1492]

Thanks guys , your answer are helpful

Sorry about the poor description about my issue, with more details, my pump is for liquid Oxigen, it is for cylinder filling for industrial welding and medical service.
I just have this pump and I have to fit it to the pressure of 3000 psi because that is the maximun limit of the cylinders. The source of my pump is a cryogenic vessel with a MAWP of 250 psi.

 

[hydtools]

Are you saying you have a pump rated to 4000psi and you want to limit the maximum delivered pressure to 3000psi?

Ted

 

[georgeverghese]

You'll probably need 2 devices that recycle excess pressure back to the source vessel:
a) This backpressure PCV set at no higher than 90% of 3000psi - this manages your normal max filling pressure operation.
b) A backup liquid service safety relief valve set at 3000psi also discharging back to the source vessel.

Talk to a process engineer who should assist with the P&I D for this and help to fill in process data / design conditions for the datasheets for these devices for procurement.

Also check that the design pressure for the downstream LO2 vaporiser is equal to or exceeds 3000psig.

 

[MortenA]

Pay attention to what Littleinch says: A PD pump is a volumetric pump. In "theory" it can deliver infinite pressure, in reality the mechanics set a limit (and then some safety device cut off before that).

In any flow system pressure and flow is interconnected. If you pump against "zero pressure" you cant create pressure without adding resistance (e.g. a valve). If your source has infinite pressure upstream this wont limit your flow since pressure upstream the valve will just increase until your valve delivers the flow from yur source. Downstream the valve the pressure will still be zero.

If on the other hand your flow decreases with increasing pressure (e.g. a centrifugal pump) then your upstream pressure will increase and your flow will decrease until dP and Q matches the capacity of the valve. Downstream still zero. Say you are filling a vessel. Your worry is that once the vessel is full then the pump can over pressure your vessel. But until its full you wont see much pressure increase. What you then need is a safety valve that will remove the liquid (this could be to the inlet of the pump). If your current pump has such a device and the S/P is too high you will then need to adjust this down (and make sure it has sufficient capacity). If it cant be adjusted then you can add an external PSV with the right S/P and the right capacity. I assume that you know liquid oxygen is a dangerous fluid to transport in piping systems?

Best regards, Morten

 

[LittleInch]

~Are you sure you know what you're doing here??

Without sounding pessimistic, I don't get feeling.

Liquid O2 is -183C. You don't pump that liquid into a standard high pressure gas cylinder.

I can only assume therefore that what you're doing, which needs to be regulated and designed and operated correctly, is gasifying liquid O2 and then compressing it into bottles.

A PD pump will just pump gas or liquid at a constant flow. The pressure comes form the back pressure of the vessel or system into which you are flowing.

In your system the pressure will slowly rise as you fill it - think of a car tyre if you need to - when it's flat the air pressure form the compressor is very low until the tyre gradually inflates.

What you need are pressure switches to cut out the pump below the 3000 limit and some relief valves. Given that the relief valves should not lift if you operate this system properly, then the valves should vent to a safe place as they are a protective device.

you don't need to "regulate" a PD pump - just turn it off once it's reached the pressure you need and put in some safety pressure relief devices.


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