Set Pressure for PRV

You will need system information, not pump information to complete this task.

If it is a centrifugal pump it may not need or benefit from a PRV.

The job of the PRV is to protect the downstream pipework against overpressure, about which no data has been posted.

The tags indicate optimum performance of the pump. You need to tell us what the system performance is. Along with all the other information such as fluids/temps./flows/pressures that you have ommitted.

Do your y and o keys not work?

"A pump doesnt increase pressure of any liquid ..."

SAY WHAT?!?!?

Please explain what happens when you dead-head a centrifugal pump then.

There is an article, very recent one, but unable to trace it at the moment, possible from Pump & Systems magazine or another. (the result of subscribing to too many ).

The gist is

The only purpose of a pump is to create a flow.

_{the pressure is created by the down stream connections}

And the article ends with ... _{(in case of a false premise like the one being made here)}

Read paragraph 2 again understand it thoroughly (ie the above one, a part of which i have reproduced) and write 500 times.

Still searching that, will give the link when available. But this (http://www.pumpworld.com/contents.htm - sorry, link no longer available) answers your assumption.

A centrifugal pump is one of the simplest pieces of equipment. Its purpose is to convert energy of an electric motor or engine into velocity or kinetic energy and then into pressure of a fluid that is being pumped. The energy changes occur into two main parts of the pump, the impeller and the volute. The impeller is the rotating part that converts driver energy into the kinetic energy. The volute is the stationary part that converts the kinetic energy into pressure

or here

A centrifugal pump converts the input power to kinetic energy in the liquid by accelerating the liquid by a revolving device - an impeller.

And though I have searched only for centrifugal, the above article as I remember was about PD pump.

I have recently read somewhere:

"A wise man told me don't argue with fools. Cause people from a distance can't tell who is who."

Is it why you are hidden under the cover of guest, not logged in ?

Why do pumps have characteristic curves, then?

After careful consideration of all the responses to the OP, I must admit that I believe that piping_engineer has given the most responsive answer to the question at hand.

In this case, I believe that the quality of the answer was commensurate with the quality of the question.

But he is 2-OT points . Is it how it works over here?

He is appropriate but not most.

does it sense that u need a PRV at pump discharge.

Does not convey much meaning But I assume he masns

"Does it make sense to have a PRV at pump discharge?"

In that case I disagree. Most of the pumps in our systems (we buy out the systems for our equipment, but drawings, specs are ours) do have a PRV at pump discharge. And that's what I hav seen in the systems that are in our capital machines too.

This is required, especially in case of PD Pumps to ensure that the flow restrictions (choked filters, choked lines,... ) do not build up the pump utlet pressure to unmanageable level.

The pumps are procured with inbuilt safety valve, the additional PRV in the outlet line is kept just below the pumps internal.

Just to give an example,

Expected Line pressure 4-6 bar (at outlet) of system.

Pump designed to carry 18 bar.

Drops (filter, cooler, pipe line, instruments..) makes the back calculated pump outlet pressure 7-10 bar.

Pump relief valve (inbuilt) set at 14 bar.

PRV setting - 12 bar.

(This will have to ensure the protection to filter in case of choking too- you don't want that a maintenance man not heeding to alarm (there are too many, pressure, Diff presseure, flow,... but still it does happen) and letting it run till the filter element collapses and clears the alarm(s)- _{(I have seen it happening quite a few times when I went to attend equipments at site).}

WHATEVER!!!!!!!

Check the shutoff head+max suction pressure. If it is above the discharge pipe/component rating then provide a PRV set at design pressure of the discharge piping.

Your PRV should be szed to discharge flow required to bring down the dischrge pressure to design pressure.

Dear ,

there is no relationship between pump and pSV set pressue .

you check design pressure of pump discharge line and PSV set valule will be the same as piping design pressure.

ex - ppdischarge piping design pressure -54 kg/cm2

PSV set presure - 54 kg/cm2

with regards

thank you "lynlynch" for appreciation we are here to get correct answers to the questions. Everyone participated very seriously to get the answer and shared their knowledge and experience. the asked question was really interesting and demanding more knowledge about pump "PIPING SYSTEMS SELECTION".

Does the term sarcasm ring any bells?

Dear Friends,

A. I agree that in 'free flow' the pumps do not create any pressure energy, but the pumps convert the mechanical energy into kinetic energy which causes the flow of fluids.

B. On restriction of flow, the kinetic energy is converted to pressure energy which is commonly known as 'Discharge Head' or 'Discharge Pressure'.

But the question is for installation of a 'Pressure Relief Valve', not for my these answers which are totally irrelevant.

1. The PRVs are always installed in pressure lines and that is why they are called 'Pressure Relief valves'.

2. The PRVs are installed to protect the pipelines, actuators, operating systems and the pump from getting damaged due to excess pressure and to keep the pump running regularly during system actuation as well as rest. PRV unloads the pressure and relieves the pump during non-actuation periods.

3. The pumps have a certain discharge pressure range and are seldom manufactured to cater exact discharge pressure requirements, i.e., a pump of 20 bar discharge pressure can be used for all systems of up to 20 bar operating pressure. Here, PRV is installed to reduce the pressure for a particular system designed for lower pressure.

4. For systems, the setting of PRV depends on the "designed working pressure" of the system. For pumps the PRV can be set just above the working pressure of system or just below the maximum discharge pressure.

5. In case of high pressure pumps, it is better to set the pressure at 10 - 12 % above the system's working pressure. For low pressure puumps the operating pressure of PRV can be set below the maximum discharge pressure of pump but above the system's working pressure. A good judgement is needed to determine the PRV pressure setting.

Regards.

Dear Friends,

Thanks for rating my answer, but it was not 'Off Topic'. I think all points written by me pointed directly or indirectly to NRV and to the question asked.

Regards.

So far you have not provided enough info. most safety relief valves are factory set and you should not try to adjust. You do not need a relief valve if the pump is centrifugal type, but if pump is positive displacement you need to go back to the system equipment and look for an ASME inspection stamp on tanks or vessels that are under pressure. Next look for the design or manufacturers data on the tanks in you system and the maximum working pressure information should be listed.

Now order a relief valve to release at a lower pressure this will protect that tank or vessel. Also inspect equipment for a flanged or threaded connection to install the relief valve. If the existing relief valve is currently on the tank leave it alone and have sent out to be tested and recertified............

Finally you need to register online with ASME and ANSI and look up B31-1 and -3 and study the codes on designing systems.

I don't know your background but you must follow the codes exactly otherwise if your system should fail due to improper or illegal tampering of the relief valve you could be held responsible and find yourself in court being sued.

I often see the following design applications:

1) For centrifugal pumps an ARC (automatic recirculation) Valve is installed on the discharge line. This Valve is set to allow the pump to maintain the minimum flow required to avoid running into shut-off pressure when the main stream flow is restricted. The recirc line is typically piped into the tank were the fluid is being pumped from.

2) For positive displacement pumps a PRV is required at pump discharge and should be set at Max. design pressure of the pump or the system, whichever is lower.