13 Nov 2000 at 7:34 pm #273873MasterPlumbersKeymaster
how often should a pressure relief valve be opened i have various answers from profesionals? thanks
13 Nov 2000 at 10:59 pm #288739
You will receive a variety of answers to your question because:
1. there are many different applications of relief valves; such as:
a. water heaters
c. pressure vessels for chemicals
d. refrigeration machinery
2. Each manufacturer of relief valves specifies on an attached tag the recommended frequency of opening.
3. A manufacturer of a machine may specify the frequency of examination aside from the valve manufacturer’s recommendations.
4. Each person you ask may be from a different vocational background. A plumber may recommend once a year for a water heater. A boiler operator may recommend once-per-week; etc. The answer depends upon the circumstances of their occupation.
This question is similar to asking how many licks you may take of a lollipop. – It depends on the manufacturer and the circumstances.
14 Nov 2000 at 3:32 am #288740
Harold dear sir, and heating guru.
According to the ASME a “Relief” valve is liquid and a “safety” is vapor (POP)
With that out of the way Section IV of the ASME and the National Board Of Boiler Inspectors (NBBI) clearly states during the heating season these devices should be tested weekly.
As a Certified low pressure boiler and unfired pressure vessel inspector I had the pressure vessels tested BI yearly and fired vessels weekly.
The problem with either a pop or safety test is the inherent danger involved by
doing this test properly.
This is exactly why I wont have a helper ever go to these tests as these wanna bee’s would end up blowing away the building or killing themselves.
When I perform these tests I do the following.
I close the “king valve”
then jump out all safety controls electrically and set the operating controller on manual.
I take a nice position looking at the steam boilers gauge and watch the gauge climb and climb and climb when the pressure gets around 14 PSI it gets to be kind of nerve wracking wondering if the safety valve(s) is going to POP
If two valves are present you keep going to make sure BOTH discharge POP to see that under a run away firing condition the firing rate input will not exceed the safety output.
On a hot water system is much less dramatic, sort of like a water balloon plopping open.
On an air compressor the pressures can exceed over 300 pounds before they POP but 150-175 is average and this I test once per year.
Most of the journeymen are NOT Qualified for these tests and they should only be performed by either a licensed Qualified Stationary engineer or certified boiler inspector Or a LMP (I being all three know what can happen if a non skilled person tried this)
What these inspections try to duplicate is a very dangerous condition where your building up enough pressure to force a safety/ relief device to open full flow.
This is not for the faint of heart BUT someone has to do it.
Harold imagine doing it on a high pressure boiler say 1,500 PSI Steam OPERATING pressure. I DID IT ONCE NEVER AGAIN
After that the 15 pounds doesn’t seem so deafening LOL
Testing these devices is very important BUT have it performed ONLY by a licensed and highly skilled person.
14 Nov 2000 at 6:22 am #288741
Dont let this lot baffel you with ballshit, just follow the manufactures instructions on your hot water system
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