Pressure Relief Valve Settings

You don't!

Safety pressure relief valves are set to max system design pressure to keep from damaging equipment!

You need to concern yourself with the high temperature issue, could be caused by a safety relief valve not being set correctly or valve with improper spring or damaged seat.

Leakage in valves cause sharp temperature rises in the oil due to friction. Check your system for oil bypass and repair these issues then your high temp issue should go away unless you have an extremely high system design pressure then you are going to have to add some sort of cooler in the system be it air or water cooling

Once you get the temp under control the rest of it is easy.

Heat is detrimental to hydraulic oil and systems so fix the heating issue first.

The problem comes in when your safety is fitted to a heat source (eg boiler), the safety start heating up from the energy coming from the boiler. We always hot set out safety valves on the boilers with our inspectors. The springs starts losing tension as the temperature goes up. Ussually a 1 bar early lift is normal.

But the reason for my question is that we have another safety valve that sits on a oil heating system that protect the heat exchanger from over pressure. The oil goes up to 180 degrees celsius and it hold safety risk to hot set this safety valve. I was looking for information from the field for alternative solution.

Thank you

OK, clarification on your question was good, please from now on include important things like what exactly it is you are working on.

As you can see I misinterpreted your question and headed down the wrong path due to lack of information.

Sorry I cannot/ will not help with boiler pressure relief issues without putting my hands on the system. Too much liability involved.

Seek help from a qualified technician.

Or, the valve makers.

Only a fool manager would ask strangers questions relating to potential deadly safety issues.

If you get it wrong, people could die!!!!!!!!!!!!!!!!!!

ASME VIII div1 UG-125 to UG-140
WP

Thank you Whitephone, helpfull information.

Are you kidding?? je

I was being sarcastic....

https://www.google.com/#q=cold+set+a+pressure+relief+safety+valve+

Got me some hits with suppliers. I deem it best to contact them and ask directly.

There should be an interest on their end to help you with this.

Cold setting of relief valves to account for the difference between testing the valve on a rig in a workshop at room temperature compared with the temperature the valve actually operates at is standard practice. As you have observed, the set pressure will generally tend to reduce at higher temperature due to the thermal expansion of the valve topworks allowing the spring to relax slightly. The required cold set pressure offset relative to operating conditions is specific to the valve hence generally the hot and cold set pressures should be included on the datasheet for the specific valve and application by the original manufacturer. If this data is not available then you could either seek it from the original supplier or, failing that, work with your competent (certified) valve overhaul shop to determine the correct cold setting by means of hot field testing - the test results then being used to inform future cold setting in the workshop.

I understand you do not want this valve to discharge while testing in service, and I am assuming you have carried out such hot testing on boiler valves utilising some variant of a hydraulic load measuring system eg Trevitester. Some of those systems claim to be able to determine the set point by load reduction at 'float' pressure immediately prior to the valve popping open i.e. testing without the valve actually discharging. I leave you to assess such claims in your situation. Also, a liquid relief valve such as on your heat exchanger will not have such a clearly defined 'pop' point (ie high lift) as would a steam safety valve for boiler applications.

Also, what is the purpose of the relief valve? Is it actually to protect against process conditions (which may be incapable of overpressuring the HEX) or is it installed just for the fire release case ie external heating while the fluid is locked in the exchanger? If it is the latter, then as long as the reduction in hot set pressure does not cause you any problems with spurious discharge during normal operation, then the reduction in set pressure relative to the design case may be a conservative result that you decide to live with - the valve will just open at a slightly lower pressure in the case of those extreme conditions arising.

Whatever approach you decide to take, ensure you keep your local regulatory inspector informed as they will presumably have to certify the resultant settings.