Replacing Relief Valves on a Boiler

boiler safety valves

The valves that need to be replaced.

Our #3 Boiler to be exact.  I guess the county boiler inspector came out a few weeks ago and made a strong “recommendation” that we replace the safety relief valves on #3 boiler.  He asked the building engineer on duty when the last time was that either the reliefs had been tested or replaced.

Apparently boiler inspectors don’t really like the answers “never” and “never.”  But this obvious dereliction of maintenance was before my time.  It’s crazy how much stuff gets overlooked at places.  Maybe the facility or maintenance staff is too busy or an emergency came up.  But the ASME (American Society of Mechanical Engineers) has codes, rules, and regulations for a variety of reasons.

Safety being the main one.

What is a relief valve?
relief valve exploded view

Internals of a relief valve.

A safety valve is a valve mechanism which automatically releases a substance from a boiler, pressure vessel, or other system, when the pressure or temperature exceeds preset limits. (wiki)

And why are they important on boilers?

Because they prevent the little pressure vessels from becoming overpressurized and causing damage.  If you are having trouble picturing what a relief valve is or looks like, your hot water heater at home has one on top and the cap to the radiator on your car kind of has one.

Boiler Code Requirements

I have no idea what the code regulations would be in your area.  You can look into it.  Around here though, pressure relief valves on boilers should be manually exercised at least 1x/month.  Yeah right.

They should be removed from the system and bench tested like 1x/year.  A bench test like this would involve raising the pressure of a closed, test system to the lifting pressure of the relief valve to ensure it lifts at the proper time.

Boiler safety valves should just automatically be replaced every so often as well, maybe every 5-10 years.

And when the county boiler inspector heard the answer that the lead building engineer gave him, never and never, he had some simple instructions.  Shut down that boiler, #3, and replace the valves.  Until you do, don’t run it.

Alrighty then.

Replacing Them
boiler pressure relief valves

Another angle of the old ones. See those welds? Idiots.

I come in Saturday night expecting a nice, quiet night of babysitting the campus and facility.  I have been a bit sleepy lately and the past few weekends have been anything but quiet.  Yeah hard work makes the shift go by quicker but sometimes you just want to be lazy right?

Walking into the shop, getting ready to do passdown, turnover, and relief with the offgoing engineer, I noticed 2 cardboard boxes on a counter.

Being the observant guy that I am, those boxes weren’t there when I left earlier so I knew the day shift engineer either had done them, was supposed to do them, or was going to ask me to do them.  Which one do you think it was?

Would I be writing about it if he did it?  Ha ha.

The Procedure

Removing the old boiler safety valves.

Removing the old boiler safety valves.

There is no real procedure for changing out the pressure relief valves on boilers.  #3 boiler has been offline for a good month or two after a weld on the feedwater inlet piping failed.  It was leaking slightly and being a pressure vessel…

Both main steam stop valves were shut, so was the feedwater line.  Pumps were off, yadda yadda yadda.

All I basically did was make sure that the boiler was vented of pressure, I did this by making sure it was vented to the atmosphere somewhere.

I then broke the unions free one at a time and then spun each valve a little to the side so I could either remove the pipe nipple or the entire relief valve.  For the first valve, I left the nipple on and it was a pain in the behind.

After getting both valves off, I started prepping the 2 new valves.  Once again my favorites, teflon tape and pipe dope.

Does it seem like where I work is a joke?

For comparison purposes.  Not too small but not big either.

For comparison purposes. Not too small but not big either.

It does to me sometimes.  Of course the 2 relief valves that were ordered weren’t the same as what was on the boiler.  One valve was identical but the other was taller.  So now, of course, like usual, poop went sideways.

Since this valve had different dimensions, the outlet piping was going to have to be altered.  Yay.  Fun times.  This was supposed to be 2 unions, 2 valves, and 2 unions – done.

Nope.  4 hours later, 2 pots of coffee, and a plethora of curse words…

It is done.  I just hope to the Dear God o’ Lord that I am not here if that relief valve ever lifts lol.  Nah, it should be fine.  I think.

And what is with every single mother flippin’ pipe joint at this place being welded together?  I am beginning to wonder if some engineer way back didn’t get his welding certification and just went apeshit welding anything and everything.

Speaking of which, have you ever heard that cute little saying – “give a boy a hammer and everything he encounters requires some amount of pounding.”  Same thing.

For the first valve, I just took it out, prepped the old fittings.  Like I said, everything changed for the 2nd valve.  I had to make a new outlet section of piping so that it could connect to the drain.  After removing the old one and putting in the new one, not only did the new one sit higher on top of the boiler but it was less deep as well.  The section of piping that had been on it was now like 2″ too short.

pressure relief valve pic

Taped & ready for the install.


After 3 hours of climbing onto and off of the boiler, I finally got it.  I needed to get 12″ of piping in between the relief and the drain piping.  It needed to have a union installed in case we ever had to remove the valve.

The discharge outlet on the larger relief was 1.5″.  Obviously us being a professional and prepared workplace, we didn’t have any 1.5″ piping.  JC.

And that is why you see that little metal looking sleeve thing there.  I needed to have 12″ of piping exposed and since we lose .5″ inside pipe fittings, it had to be at least 13″.  I prefer a skooch longer because you can always make it fit.  Too short and you are screwed.  Measure twice cut once right?

I needed to cobble together 1.5″ piping pieces in order to make a length of 13″ or so.

Wrapping Up

New valves in baby!

New valves in baby!

Thankfully I am outta here.  This is my weekend.  I did this work on my Friday night so in case anything goes wrong I won’t be here.  Just kidding.  Doing projects like this get you all hot and sweaty.  It makes the shift go by quicker plus you feel way more accomplished.

How about you?  You have any projects at work or home you’d like to share or discuss?  Come on, it would be cool to see some stuff from other people.  Let me know in the comments.  Until next time.  Stay frosty.

More Pics

I went a little crazy with my phone taking pics.  I can’t just let them sit in my library on here!  Here you go.

A piece of garbage old one.

A piece of garbage old one.  See that discoloration?  That’s a weephole.

A different shot of the new one installed.

A different shot of the new one installed.

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