Pressure relief tapping

hot_rod

Being that I'm a relative "newbie" to the steam and hydronics field, I have a question regarding the pressure relief valve on a hot water boiler. Is it okay to bush down the tapping to a smaller size or do you have to match the tapping to the inlet size of the pressure relief ? Is this according to a national code, I couldn't find it in the ASME CSD-1 standards ?

Unknown

The relief valve

outlet tappings are not supposed to be bushed down as far as I am aware Mike. You may want to run this one by the folks at Watts or ConBraCo. By the way....are you the Mike Downey of University of Rhode Island fame?

Glenn Stanton

Burnham Corp.

seabee570

RELIEF TAPPING

as an operator of high pressure steam boilers and license holder of several steam engineers licenses,you are never to reduce the relief valve fitting..i.e.-if a 3/4 inch relief valve is supplied,the opening into the boiler/device should be the same...I know the ASME covers this but do not know what section...reason is that the relief valve relies on a certain size surface area in order to operate properly

Tony Conner

If You Check Into..

...the sizing of safety and relief valves on things like boilers, you'll find that the codes leave it up to the manufacturer to size these. There is no set, approved way of performing this calculation defined in the ASME codes. It's left up to the designer to provide adequate safety or relief valve capacity.

It's not that you CAN'T drop the size of the relief valve on a boiler, I believe you can. However, you'll likely have to go through some sort of "code calculation dance" for the inspection authorities, and that will probably cost you far more than the valve is worth.

I'd be VERY reluctant to get involved with basically re-sizing a boiler safety or relief valve, even in a situation where the burner input has been significantly reduced.

October Home

I have a relief valve question

and found this website:
http://wattscda.com/pdf-files/F-52Q&A-9948.pdf

But I can't figure out if this piping is correct: This is a Slant/Finn L 30 P and shouldn't the valve be comming directly from the boiler? and aren't two elbows one too many? There's also a coal auxillarly boiler with this system. An HS Hedler-Tarm, Model T 202. I forgot to get a shot of its relief valve but it's on the supply side piping. I wonder how that relief valve should be piped? The Home Owner says that it spits periodically.

Thanks for your help, Wetheads, always,

Arlene

Tony_8

valve location

(1) As far as I am aware, as long as the relief cannot be isolated from the boiler (by a valve) it is ok. Have seen many in the piping and Watts Dual Controls are still made and installed and are not "on" the boiler.
(2) Most solid fuel, pressurized boilers "runaway" to an extent, occaisionally. Mostly when the weather warms quickly and the system is hot and has nowhere to go. It just can't be shut off as easily and completely as other fires. This is one of the reasons most solid fuel boilers are "open" systems, that and ASME.
I have the "joy" of dealing with many solid fuel units operated in tandem w/gas, oil & LP systems all the time. The Tarm equipment is one of the best and cleanest, IMO.

October Home

This coal boiler

I inspected yesterday is lovingly maintained by the homeowner who installed and piped it. When the new homeowner moves in she'll need to find someone who can maintain the system. I told her I'd try to find her someone. Glad to hear you like Tarm.

Thanks for the feedback.

Arlene

Don_4

Relief valve

regardless of the code issues the relief must at least be sized for proper capacity (btuh)to be safe. The reason the valve may be spitting could be in part due to improper mounting. The relief valve should always be mounted in a vertical position and then pipe close to the floor or preferably to a drain. No reduction (pipe size) is allowed on the discharge of the valve.

Bob_19

Clarification;

A safety valve and a P/T valve operate on different priciples and are coded seperatly.
A safety valve has to relieve a set amount of lbs/steam/hr, it can not let the boiler raise 6% above it's MAWP, and can not blowback more than 4% of it's popping pressure, but more than 1% if running 200# to 300#, excessive blowback is very dangerous.
Safety valves pop open and slam shut smartly and you can NEVER reduce the valve fitting nipple in the field. Unless you are a PE familier with pressure vessels and ASME codes you should not alter any safety device.

P/T valves are either pressure or temp, which ever raises first above set point it will open, problem is they only have to keep from going over the valve setting and that's it, if you reduce the input fitting how are you going to know if this will happen with-out first doing capacity calculations.

I will most definitly agree with seabee, never under any circumstance are you to alter in the field, the consequences are tragic.