"Pressure regulating valve" need help with what happens at no flow
"Pressure regulating valve" need help with what happens at no flow
(OP)
We have installed a pressure regulating valve from ARI in our thermal fluid system. The point was to reduce the pressure in a secondary heating loop to about 70 PSI to keep a relief valve from opening downstream that is set at 85PSI. There is a centrifugal pump after the ARI valve with a check valve after that prior to returning to the primary loop.
We tested the system today with both the primary loop pump and secondary loop pumps running. The Primary pump produced about 120 psi on the inlet of the ARI valve. A gage after the ARI valve read 60 PSI which was great.
Problem came after we shut off the secondary pump and left the primary pump running which still showed 120PSI at the inlet of the ARI. However after the ARI valve gage now shows 85-100 fluctuating alerting us that the relief valve was opening spewing oil out into our vent tank. Luckily we caught this before there was any mess but I am trying to understand what happened. I have attached a diagram of the pressure regulating valve
We tested the system today with both the primary loop pump and secondary loop pumps running. The Primary pump produced about 120 psi on the inlet of the ARI valve. A gage after the ARI valve read 60 PSI which was great.
Problem came after we shut off the secondary pump and left the primary pump running which still showed 120PSI at the inlet of the ARI. However after the ARI valve gage now shows 85-100 fluctuating alerting us that the relief valve was opening spewing oil out into our vent tank. Luckily we caught this before there was any mess but I am trying to understand what happened. I have attached a diagram of the pressure regulating valve





RE: "Pressure regulating valve" need help with what happens at no flow
RE: "Pressure regulating valve" need help with what happens at no flow
However, your description of the relative positions of pumps and the ARV PRV are not 100% clear to me.
If you could attach a system sketch that would be most helpful.
For example, what is at the "end of the line" for the secondary loop that maintains the 70 psig operating pressure?
RE: "Pressure regulating valve" need help with what happens at no flow
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: "Pressure regulating valve" need help with what happens at no flow
If you get a proper tight shutoff control valve not this cheap relief valve then you might stand a chance, but the other posters are right, generally you can't rely on these valves to reliably seal on no flowt.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: "Pressure regulating valve" need help with what happens at no flow
But this point certainly doesn't explain the system's behavior (other than it has no chance of working as intended).
All the more need for a system sketch.
RE: "Pressure regulating valve" need help with what happens at no flow
So it seems like we either have to install an automated shutoff valve prior to the valve or install a different unit. We have 3 of these so this is going to be a pain. I am guessing a new unit is the best option. Any more thoughts? Or advice on a brand/model recommendation?
RE: "Pressure regulating valve" need help with what happens at no flow
So what do you want it to do?
RE: "Pressure regulating valve" need help with what happens at no flow
Only a drawing will sort this out.....
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: "Pressure regulating valve" need help with what happens at no flow
You need a new unit. At running pressure you have just got lucky and the pressure drop across the valve you currently have when open and flowing is apparently enough to reduce your downstream pressure to the right amount. An orifice plate would have done the same thing.
You need a regulator controlling on downstream pressure. Google "pressure regulator" and ensure it controls on downstream pressure when you talk to the vendor. If you specify tight shutoff you might get that to start with or at least it might limit flow past the valve to an acceptable level or time to go and turn the loop off manually with an isolation valve. If you have clean fluid which is well filtered and the seals are good it might seal for quite a while, but there are very few people who would rely on a regulator to isolate flow.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: "Pressure regulating valve" need help with what happens at no flow
RE: "Pressure regulating valve" need help with what happens at no flow
RE: "Pressure regulating valve" need help with what happens at no flow
Pic1 was the secondary loop pump
RE: "Pressure regulating valve" need help with what happens at no flow
RE: "Pressure regulating valve" need help with what happens at no flow
Looking at this again though the valve MIGHT be acting as a constant DP valve if it takes account of the downstream pressure on the surface of the disc. The spring then adds up to about 60 psi so added to the 60psi you want d/s you want gives you 120. This depends on the upstream pressure being fairly constant and hence what you actually have is the upstream pressure minus a fixed amount as provided by the spring. It's not easy to tell if this is the case and nowhere near as good as a proper downstream regulator which will give you a fixed downstream pressure regardless of the upstream pressure.
If this is the case then either the valve is passing (quite likely) or your NRV on the pump is passing (also quite likely).
Your diagram is fine, but the control line from your pressure reducing valve is correct as far as this is what you want, but isn't correct as far as the valve you have which is a pressure relief valve, albeit probably being influenced by the downstream pressure.
I think you have a constant Differential pressure relief valve installed but with the difference between what you want (60-70 psi) and relief pressure (80 psig) there isn't a lot for the valve spring to play with and seat the disc.
does that make sense?
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: "Pressure regulating valve" need help with what happens at no flow
RE: "Pressure regulating valve" need help with what happens at no flow
In such applications, the minimum flow should be routed back to the supply tank.
You can fix this by installing a tee where the valve is currently located and taking the branch to feed you min. flow valve back to storage.
The valve is working fine, but it needs to be piped correctly.
Good luck...
RE: "Pressure regulating valve" need help with what happens at no flow
The design looks workable. To prevent the PSV from lifting I'd put actuators on the first valve off the loop and the last valve off the loop (after the check, which is just as prone to leak in a no-flow situation as the PR) to slam on pump down (restriction orifices on the main loop and secondary loop might have allowed natural convection, with the pump off, but you didn't provide them so in a pump-down scenario you aren't going to get any flow to the heat exchanger loop at all).
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: "Pressure regulating valve" need help with what happens at no flow
Sorry but what you have written makes no sense at all (at least to me).
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: "Pressure regulating valve" need help with what happens at no flow
Please correct me, but I can't see any sensing port either on the drawing or on the photos. What I can see is a spring acting via a spindle onto a disc. The thing making the disc overcome the spring force via the spindle is differential pressure across the disc no?
If the OP had gone a bit further down the fig 753, it would have been much clearer. See attached and go to page 3 where it says the application is a "spring loaded differential pressure control valve".
http://www.ari-armaturen.com/_appl/files_tb/files/...
I agree with you that it could work and apparently does when flowing and you have 120psi in the inlet, but needs better isolation, but the valve is still not what the OP asked for.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: "Pressure regulating valve" need help with what happens at no flow
Yes, the valve in question does respond to differential pressure and the down-stream pressure must be taken into account when adjusting the pressure setting. So it says in the operating instructions. But note the following:
"Pressure regulating valves, spring loaded" are quite distinct distinct from
"Pessure reducing valves." One controls upstream pressure and used for minimum flow relief on pumps as the current installed valve does and the other controls the down stream pressure.
RE: "Pressure regulating valve" need help with what happens at no flow
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: "Pressure regulating valve" need help with what happens at no flow
We can check the spring force tomorrow. I did not really get a chance to play with it much yesterday and maybe if I would have made the spring force higher it would have shut
Since our primary pump is always at 100% and the pressure really doesn't change much, I guess I don't see a problem with using the pressure reducing valves if we verify the ARI and Check valve shuts 100% - or maybe we install electric actuators on our gate valves before the ARI and after the pump
Definitely agree the pressure regulating valve would have been the correct choice. However, according to ARI their regulating valve can not handle the 400F temp of the thermal fluid so they are recommending a control valve which is even more money but we will get it one way or another.
RE: "Pressure regulating valve" need help with what happens at no flow
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: "Pressure regulating valve" need help with what happens at no flow
RE: "Pressure regulating valve" need help with what happens at no flow
Of course the root cause is the pressure difference between your loops. DO you actually need to operate the primary loop at 120psi instead of 70?
If you do you might want to consider putting a single control valve on the secondary loop line down to 70 psi and a pump to get it back to 120 psi (where your two vertical arrows are in the sketch) and just getting rid of the three reducing valves? Just a thought.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: "Pressure regulating valve" need help with what happens at no flow
RE: "Pressure regulating valve" need help with what happens at no flow
My guess is that you are leaking through the PR, the check, or (most likely) both.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: "Pressure regulating valve" need help with what happens at no flow
let us know how it goes with whatever changes you make.
good luck
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: "Pressure regulating valve" need help with what happens at no flow
RE: "Pressure regulating valve" need help with what happens at no flow
-spring loaded check valve of some design maybe the kind with 2 flaps? not sure.
-actuated butterfly shutoff valves with high temp elastomers - ball valve as alternative
-regulating valve to replace the reducing valve
We think this will put is in a good position. Any thoughts or suggestions?
We will be reviewing all the cut sheets prior to accepting anything
RE: "Pressure regulating valve" need help with what happens at no flow
Now sounds like a proper system to me. You might still get an initial flow from the relief valve, but should be lower and stop once you close the butterfly valves.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: "Pressure regulating valve" need help with what happens at no flow
so question - in your experiences is a class IV valve good to prevent pressure from equalizing from one side to the other? I know the description of what that class of valve does and it sure doesn't seem like it would work good here...
"Intended for single port and balanced single port valves with extra tight piston seals
and metal to-metal seats.
• 0.01% leakage of full open valve capacity.
• Service dP or 50 psid (3.4 bar differential), whichever is lower at 50 to 125oF.
• Test medium air at 45 to 60 psig is the test fluid."
So if there is 120GPM water should you expect some amount up to 1.2GPM to leak by? Assuming less since the test medium was air.
Or should I be looking for strictly class VI? Thanks
RE: "Pressure regulating valve" need help with what happens at no flow
Class IV is pretty good and should do fine for your purpose, but as we've all said a lot of times before control valves are not as good at isolation as isolation valves. Horses for courses and all that.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: "Pressure regulating valve" need help with what happens at no flow
The only way to get absolute system isolation is with double block and bleed arrangement, not practical for many applications.
An rule often overlooked in fluid system design: The fluid system must be designed to operate satisfactorily with valves that leak, or with valves that do not leak. Good engineering practice generally dictates this rule be followed.