Using air to find a steam system leak

Jeff_44

I've read a few posts about using an air compressor to test for a leak(s) in a steam system. I have a small leak somewhere and need to track it down. I plan to exchange all rad vents with plugs and then fill the system with air - the question I have is - where is a good place to tie into the system? I have a port on the boiler for skimming, would that work? Or how about on the top valve of the site glass via the pigtail?



Thanks

pipeking

anywhere

convenient above the water line. be very careful not to put to much pressure in, 5-7psi max, i prolly wouldn't exceed 5psi. and then go around a spray all your joints with leak-detector. good luck

Hap_Hazzard

Icesailor is probably the expert on this

I'd try to isolate as much as possible. If you suspect the return, try disconnecting it at both ends, if you have a convenient union at each end, cap it off at one end and connect the pressure hose to the other end. This way you won't need to worry about limiting your pressure because you're only pressurizing pipe.



If you really need to pressurize the system, you have to either limit the pressure to < 15 psi or remove the PRV, and if you do that you should probably remove the gauge and pressuretrol too. Even then I'm not sure how much pressure you can apply to it. There's got to be a reason why they use 15 psi PRVs on them.

icesailor

Leaking air:

The way I see it, just pressurize it to anything under 15#. Pick a pressure less than the PRV. I have a portable air compressor that I could use with a nail gun or pumping up tires. It has a primary/secondary regulator. The pressure switch shuts it off at 140# but I can screw the regulator out so the outlet pressure is 0# (Zero pounds). There's a quick disconnect connection on the compressor. I have a 50' quality hose with 1/4" matching quick connects. I have a rig with a boiler drain on one end and a quick connect hose connector on the other. I have a ball valve between with a tee fitting and a 0-100# gauge on it. Connect the "rig" with a double hose connection (Washing machine hose) to the thing you want to test. Hook it on and let her rip. Start at zero and slowly open the regulator until you get the pressure you want. It doesn't matter where you connect it but you will want to have a hose at the bottom of the system so you can drain it. Any place I can connect to a 3/4" or 1/2" boiler drain.

You will find out which air vents work and don't work. Now is a great time to take the old ones out and put them back with PTFE tape and paste so the next time, it will be a gravy job.

Once pressurized, spray it with gas leak detector or soapy water in a spray bottle. If it bubbles, it's leaking.

Jeff_44

Thanks -

This is very helpful. I'll get to work.

Pumpguy

One trick

we use to find leaks in return lines in 2 pipe systems is the peppermint test.  We valve off the return at the condensate receiver and temporarily make a connection to the return line upstream of this closed off valve.  At this connection we blow in peppermint vapors and then walk the building sniffing for peppermint vapors. 



This is usually done on vacuum return systems where we temporarily convert the vacuum pump into a low pressure blower. The vacuum pump's air discharge is temporarily piped to the upstream connection.  Adding peppermint oil to the vacuum condensate receiver causes peppermint vapors to blow out the air discharge.



Maybe you can use this idea on your system?

icesailor

Peppermint Vapors:

I just pour the oil into the washing machine hose and let the compressed air blow it around.

There was a big blow yesterday where I work and I got stuck overnight. This AM, I photoed some of my "Rigs" for ideas to anyone. One is for air testing LP gas at 12# so if I find a leak, I'm not sweating a blow up. Another one is a 5# gauge for gas testing that the inspector likes to look at.

I replaced a boiler that gave up its life during the cold. I drained the house but the cold might have gotten it. and the heat was really suspect where the boiler had gotten religion and become Holy. So I couldn't blow out the monoflow piping. With one connection, I was able to test the hot and cold potable water and the boiler and piping at less than 30#.  I had no leaks. Thank Goodness. It would have been a dig/crawl.