Another reason to always check relief valves!

Dale

Always look at the relief tag. We have seen hot water relief on not only hot water boilers but steam boilers, pressure was low but relief was blowing a little steam, hmm steam at 212 hot water heater relief temp at 210.

Glenn Harrison_2

And always check their ratings too.

I thought I would pass this along to everyone. I was talking to one of my co-technicians, and he told me he was working on an old Amer. Stndrd. boiler last week. The call was no heat, circ not running, new customer. Bad motor on a B&G Series 100. He quoted new motor, and new NRF-22 with draindown and refill. Customer went for motor. He replaced the motor, then was looking over the rest of the boiler, and noticed the pressure guage was at 55 psi, and the relief was dry. So he carfully drains some pressure off the boiler, to test the guage, gets to 0, and opens the fill and fills to 12 psi automatically. So guage must be ok, and relief bad. He looks at the valve and can't find the pressure rating. So now he calls me, and I ask him to read all the info to me. Starts reading , blah blah blah, 210º, 125 psi, long pause as we relise what he just read. Then I say "some idiot put a water heater relief in that boiler. No wonder why it didn't blow". Thanks god that motor went bad, or I can't even imagine what would have happened, but it sure would not have been good. So he imediatly tells the customer that it has to be replaced. Drains the boiler and replaces it, and drains the expansion tank which was obviously water logged.

Moral of the story, watch out, and check everything. You NEVER know what the guy before you (or homeowner) before you may have done, that is just plainwrong and stupid.

Mark Eatherton1

Makes you wonder...

How many of these things are out there. Also makes one wonder if the American boilers aren't somewhat under rated in thier vessels capacity to withstand prressure. German boilers are typically higher rated, and I know they typically test at pressure 2 X the rated capacity.

I am in now way condoning the operating pressure of a vessel being higher than what it is technically rated for, but makes ya wonder...

I've seen roughly half a dozen of the relief valves you mention on misapplications. Never seen a boiler that died an early death due to excessive pressure though. Usually oxygen involved.And associated corrosion.

Makes ya wonder...

And I thoroughly agree with relief valve testing. If it sticks it NEEDS to be replaced. It's in the code.

ME

Dale

Boiler manufacturer can change

One of the manufacture reps said almost all boiler manufacturers will sell a regular boiler special ordered to a higher test pressure tag. Say you had a 6 story building you could get the same boiler that had a 30 pound tag with a 50 pound tag, the factory just subjects the boiler to a higher test pressure, I don't know how high they'll go. Maybe Glenn S. can comment.

Unknown

It Varies

Our Galaxy GG water boilers are rated at 100 PSI working pressure, and can be ordered with a 30, a 50, or a 100 PSI relief valve.

Our Galaxy GX series water boilers only go to 50 PSI working pressure.

These are written on the rating plate label.

Noel

Mr. Smith

well I think

I have you guys beat!!!

I serviced a boiler a few eeks ago, laars mini therm.

they were complaining of banging noises in the radaint floor systems. they had just had it serviced by someone else about a month prior to me, but didn't trust the guy that was there, so they called me.

the pressure on the boiler was running 55lbs, ex tank was water logged, and where there should be a pressure relief......had been capped off and removed!

funny thing, but the drain line that ran to the outside was still there! the owner told me she was worried about the thing exploding!

pay attention out there!

jim sokolovic

No \"custom\" pressure testing allowed...

All boilers that are ASME certified have to be factory pressure tested at 1.5 times the heat exchanger's rating (for us, the ratings are 50 and 100 psi, as Noel said). We offer various relief valves that discharge at or below the heat exchanger's rated pressure. The only tests that are done at higher pressure are during the prototype phase of development, not for any customer's specific request.

Dave DeFord

Just a (not so) silly suggestion..

Is there any reason that the tapping for the relief valve needs to be a standard thread? In know in the steel mill that I worked in the oxygen was always a LH thread so you couldn't hook an air hose up to it. It seems to me that the same thing could be done for relief valves. Make some sort of unique thread so you couldn't cap the relief tapping. You could still make nipples etc. if they were needed just make it illegal to make caps for that size thread. Would it be fool proof? Probably not, I guess you could still have someone machine up a cap for that size thread but it would keep the idiots from blowing themselves and their neighbors to kingdom come with something they bought at HD! Just a thought.

Kal Row

2x pressure

is there a record, of a court marshal of a submarine captain who went to twice the pressure depth rating of his sub? - as far as i can recall, we lost two subs - one to a fire, and one, to being hit by it's own torpedo -
never heard about a 2x pressure depth crush - and we have had our share of stuck plane accidents taking subs way down (past 3x), where we lost people to individual compartment flooding but never the whole sub as far as i know

most hot water boilers ship with 30lb valves but would work fine at 30lbs with 60lb valves - which you would need on a 8 story hotel with an array of staged small boilers - the manufactures would never stick their neck out though - that's why lots of people out there are using good old fashioned gas domestic hot water heaters, it's the least expensive heat source with a high pressure rating!!!
i am expecting to get completely chewed up on ths one!!!

Unknown

Wasn't that one the Thresher?

Maiden voyage, dove and crushed?

Noel

Jim S

Braze joint let go

Sprayed the electrical panels on the sub,I beleive they had started to head towards the surface ,but with no power it just slid backwards until it imploded.

I believe that was also the first and last time that they used brazed joints in that application now everything is welded.

Glenn Harrison_2

Same Tech Found another one with wrong relief

Went to a call to repair a water leak, and found 50 pound rated Bryant boiler with 75 pound relief valve and prv set to fill to 35 psi. He replaced the relief with 30 pound rating and replaced prv, filled to 12 pounds, bled radiators, and all working well. This was a 2 story house with basement. Ms homeowner says her husband did work on that boiler before his passing. Must have been from the Tim Allen school of boilers, More pressure argh! argh! argh!

Kal Row

pump away, + maintain NPSH to prevent caviation...

in most older systems the pump was on the return, (for cooler seal operating temperatures), and the expansion tank was on the discharge side, - the problem with this system is that, the pump is pumping toward the point of no pressure change, so it can't increase the pressure, so it must create a suction, which gives you two problems:
1) if there is a return restriction, you will drop the system pressure to the point where you suck in air,
2) with higher temperatures, the pump will cavitate because of the sudden drop in pressure in the eye of the pump, even if the temperature/pressure is above the boiling point of water, the sudden drop causes a exploding/collapsing bubbles in the eye of the impeller, eventually disintegrating it (see note 1),

the quick'n'dirty solutions to both problems was to greatly increase the system pressure - the correct solution, would be to put a wet rotor pump past the expansion tank - (HOME DEPOT only charges 57 dollars for a taco 007 - so it's not exactly an expensive solution)


note 1) water has unique properties due to it high surface tension, it is the best refrigerant - IE it absorbers/releases 970btu per pound on a state change (liquid to vapor - etc) as opposed to a regular fluorocarbon refrigerant's 144btu per pound, under pressure is resists state change, for eg, water from a warm cloud layer falling through freezing air wont freeze because of the increasing pressure, but the minute it stops, the super cooled water freezes instantly, producing those beautiful but deadly ice storms, conversely water at 190 degrees and 12lbs, going into the eye of a pump, will explode due to the sudden pressure drop, even it the mean pressure is above the boiling point of water, because it was the surface tension that keeps it from boiling in the first place, the flow into the eye of the pump breaks the surface tension and the water goes boom!!!,
thus manufactures tell you to keep the NPSH (NetPositiveSuctionHead) as high as passable - the sudden collapse of the bubbles, even tiny ones, send a shock wave into the impeller, wreaking it in short order, funny thing though, those cheap, soft and flexible plastic impellers they use today, handle this much better, the shock wave goes right through them, and exits right at the outside edge, where the faster/denser water, deflects it, of course if the cavitation is strong, the shockwave will continue to the pump shell and blow it up
- dan holohan tells of the time he pressure tested a pump by closing the isolation valves and walked away forgetting to open them, and in 5 minutes, the whole show went boom!!! with pump shrapnel everywhere. So if the system is air free, and the pump has good bearings, but still sounds like it's moving gravel, then drop the water temperature or increase the suction pressure - before it blows!!!

Glenn Harrison_2

I completely understand the concept of

raising the boiler pressure to reduce air noise and possible cavitation. I've done it my self a few times. But putting the 75 pound relief on a 50 pound rated boiler is just unsafe and wrong in my book, especially when nothing else is rated for over 30 pounds. Plus this system worked fine after heating up and going from 12 psi cold to 15-16 hot. If I remember correctly, the expansion tank was almost water logged creating the 35 psi pressure. Maybe I'm being anal and overprotective, but I would much prefer it this way than being a slacker and having a tragedy occur.

Kal Row

ok

it's not anal to stay within the namplate rating
cause if anything goes wrong and you were outside the
rating, - lord protect you from the legal system

on the other hand if you have a have large and tall
multi-dwelling, and the pump bypass dumps 60lbs of head
into your boiler loop, and pops the relief valves on a
warm day with most of the zones closed, the fresh water
flowing into the system will destroy your cast sections,
the very thing was on one of dan holohans basements tapes
on hvactv.com

so now your choices are :
1)very expensive high pressure boilers
2)cheap regular hot water heaters
3)flat plate heat exchangers to mechanically isolate the
boilers from the high pressure load

i dont like any of the above solutions - i would rather put
in a primary/secondary with a closely spaced tee injection,
so that the system pump in bypass mode doesnt dump it's
head into the boiler, and run the whole show at 5.8lbs per
ten feet of height with an extra 15 pounds for the reliefs,
i would feel real comfortable with a 5 story system at
25psi and 40psi relief, with oversized expansion tank or
two smaller tanks and an alarm sensor on the relief
slant-fin's manuals say, you can run it 5psi below the
relief vave rating,
ziggi's new book says most residential units wont blow
until 3 to 4 time the pressure vessel rating - so running
it to the edge of the rating shouldn't be a problem - especially if you have a second relief in the water
feed's backflow preventer

the problem is that i haven seen or heard of a lot of
overpressure ruined systems, most of the time the reliefs
open too early, my sister-in-law's 30psi relief starts to
drip at 20psi, i leave that one alone since it's a larrs copper convector, and have no idea howmuch pressure it
can handle,

i am waiting for people to relate their stories of
overpressure ruined systems, so that i can learn from
their experience