Replace boiler pressure relief valve after it blows?

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#1: Post by itsallaroundyou »

after reading and scanning literally hundreds of threads here and at CG, knowing this question is answered somewhere, i have to just ask: how many times can a safety valve blow due to over pressure before its kaput? mine popped for the first time this morning (i bet its because i've been toying with the idea of replacing the livia with a cremina, and now i have to keep it around to fix it).

i'm confused because i've read threads that talk about them blowing everyday (?!) before they were replaced, and others that blew once and were replaced. some threads say the spring can wear out, some say it won't. of course i'd like to err on the side of safety, but if there's no need to spend $50 on a new one, i'd like to go that route.

tips, comments, advice, and stories of machines going haywire just before they are replaced are welcome :)
"If it wasn't for venetian blinds it'd be curtains for us all"

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#2: Post by another_jim »

I don't think the number of times it opens has anything to do with it needing replacement. The spring might get a little looser, making it open at lower pressure, but that is not a safety hazard. Eventually it would open below 1.5 bars, and then it would need to be replaced.

The opposite seems more dangerous. If the spring rusts, freezes, or otherwise gets stiff from non-use, that would raise the pressure at which it opens. Fortunately, pressure stats go bad often enough so that the safety valve gets a test and a workout every few years.
Jim Schulman

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#3: Post by stefano65 »

Yes, like Jim says
the pressurestat and scale build up are normally causes for safety valve to go bad
it is true that the spring will became weak with years of pressure pushing against it
eventually it will start to leak
for 20 to 30 dollars
IF they are slowly leaking is worth the expense versus
a pressurestat and heating element over working because of the leak
and also the mess they can create when they blow
Stefano Cremonesi
Stefano's Espresso Care
Repairs & sales from Oregon.

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itsallaroundyou (original poster)
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#4: Post by itsallaroundyou (original poster) »

Thanks for the feedback. i pulled the valve off today, and checked that the spring would move freely under pressure, and added some teflon tape to the threads and reseated it.

i still get the occasional hiss from it (not even enough for me to see any steam or liquid though), so i think, stefano, your advice fits to just replace it to save the wear on my other components. i think it blew in the first place due to a sticky pstat. i managed to breath a little life into the diaphragm with my needle nose pliers (i have a MA-TER) so for now that seems like it did the trick.

i've watched the pstat/element cycle about 20 times now, and its very consistent, and stays in range on the gauge, though i'm still a little weary of leaving it to come on with a timer (it might not be my alarm waking me up tomorrow morning :) what do you guys think--when is it safe to trust it is working properly again? i'll probably let it cycle for at least 2-3 more hours tonight before shutting it off.
"If it wasn't for venetian blinds it'd be curtains for us all"

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#5: Post by acquavivaespresso »

itsallaroundyou wrote:i managed to breath a little life into the diaphragm...
REPLACE that pressurestat, it is supposed to keep your boiler at 1.5bar, if it let the OPV blow that would have been at least 10bar (you should have that specified in your instruction booklet). Do not worry for the OPV spring : they are normally stainless and do not rust and should they loosen a little bit it would open say at 9bar? so what's the problem, and anyway most OPV are adjustable and you can always put that back to open at the original pressure: If your boiler had a resettable safety thermostat you could always make sure (it is actually the manufacturer who makes sure) that you do not even get close to that 10bar(?) limit ( you know, the higher the pressure the higher the temperature)...and the OPV would just sit there, just in case everything else goes bad. Also the OPV will not get clogged with lime scale since steam is scale free, having already deposited as water got heated....

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#6: Post by fredfal »

10 bar seems quite high.

I don't recall exactly the indicated pressure of my Brewtus when the P-Stat quit, but it was still indicating (i.e. not off-scale) and the scale for the steam boiler only goes up to 2.5 bar. It must have been around 2 bar when the relief valve kicked in.

I'd imagine it's in that 2 bar neighborhood.

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#7: Post by HB »

acquavivaespresso wrote:REPLACE that pressurestat, it is supposed to keep your boiler at 1.5bar, if it let the OPV blow that would have been at least 10bar...
I think you misunderstand; the steam boiler pressure relief valve opened, not the hydraulics system, which is gated by the OPV (also referred to as an expansion valve).

A bit of background for those following this thread... Most espresso machines include a pressure test certification of the boiler from the factory. The steam boilers I've seen were tested at 2.0 bar and the pressure relief valve opens ~1.6 bar. The expansion valve on a rotary pump is typically regulated to 12 bar; it's purpose is to (a) relieve pressure when the boiler heats the water in the (closed) hydraulics system and (b) relieve pressure if the pump bypass valve fails to open, preventing the system from pressurizing beyond 12 bar. For vibe pump machines, they're typically regulated to 11 bar in conformance to ESE pod standards (or so I've been told, I don't use pods).
Dan Kehn

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#8: Post by Instinct »

8) As per safety standards the boiler safety valves are preset to open at 2.5 bar, if it is a good quality valve subjected to safety tests it will come with a certificate. It blew simply because the PRESSURE STAT has failed to open the contacts at 1.1 or 1.5 bar (Depends on what you set this at on set up). It has Nothing to do with anything else. Scale built up will cause it to leak but not blow! And as these are preset to safety standards it is Dangerous to dismantle and clean. NOT WORTH THE LAW SUIT if someone is injured. They are also meant to be tested every 12 month.
As for the 10 bar ????? Do you know how much pressure is 10 bar. 140 psi, at 140 psi your boiler temperature would equal approx 170 Deg C your heat exchanger temp would exceed 200 Deg C, At this stage you and all around would be covered in boiling hot water.