Myth or no

Bobby_2

Very good question. Interpretation of code (seeing is how I've found no absolute number)would be by the AHJ and in my opinion would be on a case by case basis. Depending on the state and code used.The 2003 National Standard Plumbing Code, Section 10.16.6f: If the point of disposal is outside the room or space in which the relief valve is located, an indirect gravity drain shall be provided from the room or space to the point of disposal. Indirect waste pipes shall be sized according to Table 10.16.6 . A visable air gap shall be provided in the room or space in which the relief valve is located.

According to the 2003 IMC Section 1006.5 the intent of this section references situations of "additional lenght". Any lenght of piping and fittings would cause a pressure drop between the boiler and the safety or relief valve, allowing the boiler pressure to rise above the opening pressure of the safety and relief valve. The requirement to drain by gravity is intended to prevent water from standing in the discharge pipe and causing corrosion damage to the device and/or creating a blockage or restriction. Water or condensate trapped in a discharge pipe would also act as an obstruction by creating a backpressure that would affect the capacity and operation of the relief valve. In the case of a steam safety valve, any standing water in the discharge pipe could cause severe water hammer and therefore damage the piping because of the velocity of the steam and rapid expansion of the standing water. Because the discharge from any safety or relief valve is a threat to both the building and its occupants, as I've stated above should be individually evaluated to prevent the potential discharge from being hazardous.


Robert O'Connor/NJ

Johnny Hamilton

Myth?

I have heard that only so many elbows can go on a relief valve but no one seems to be able to find a written requirement about this. Has anyone else found any written confirmation or is another myth?

Dale

fittings

> I have heard that only so many elbows can go on a

> relief valve but no one seems to be able to find

> a written requirement about this. Has anyone else

> found any written confirmation or is another

> myth?

Dale

fittings

I found language in my states pressure vessel code on the inlet to the relief "directly on or as close as possible" the discharge piping must be pitched down from the valve and at least valve size, no mention of elbows.

jackchips_2

How many

were you thinking of using Johnny?

Jack

Johnny Hamilton

Myth?

Dale,
There was no particular number but the myth keeps coming up and we were trying to determine if there was some magic number of feet of pipe or elbows.
Thank,
Johnny

Johnny Hamilton

Myth?

Thanks for the answer. Often drawings called for discharges to be taken the closest floor drain but that might be in the middle of the floor which would make it a tripping hazard. I think you are right in deciding that the best answer depends on the layout and situation of each occasion.
Johnny