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LP gas valve

lchmb
lchmb Member Posts: 2,997
Tim, asking for a friend so information is a little sketchy until tomorrow. Two other tech's have been working on a WM CGI boiler. Issue being is odor's in the building. A pressure test was performed, found  a drop in pressure. Check all piping up to the gas valve, no leaks found. Seem's like a simple thing, replace the gas valve. That was done, and still a leak. So one of the tech's replace's all pipes from the tank to the gas valve. Still leaks. Disconnect the gas valve, plug the line, no leaks. OK...so 5 gas valves later, the gas valve is installed, a pressure test done, no drop in pressure. Run the unit 15 minute's, perform a pressure test, drop in pressure (can you hear the head banging off the wall?) They indicate there is no stray voltage to the gas valve, and that proper voltage is going to the gas valve while it is running (after this, all wires were removed and still a drop in pressure). They also went so far as to disconnect and set in place a temp tank and replace all regulators. Pressure's are 11" flow to the unit and lock up is 11.4"...Any thoughts, suggestions?

Comments

  • furnacefigher15
    furnacefigher15 Member Posts: 514
    Leak when?

    During operation? If this is it, I would look at the pilot and pilot tubing, gas manifold and orifices. I would also look at the flue piping, and castings for blockages.



    During off cycle? Look at the piping, and pressure test ports.



    All the time? Any of the above.



    5 gas valves? Come on, that's crazy. Are they severely over tightening the valve, or have excessive pipe weight on the valve?
  • bob_46
    bob_46 Member Posts: 813
    Pressure

    What pressure was used for testing ? You are not supposed to test against a gas cock let alone a control valve. Always disconnect the appliance from the gas line and cap the line.

    Most gas valves are only rated for 1/2 psi max .
    bob
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    I assume they

    are testing after the second stage regulator with a water manometer located at the gas valve inlet or as close to it as they can get? They have pressurized the line then taken a little pressure off the line and isolated it away from the second stage regulator. How long does it take for pressure to drop?



    What is the make and number of the gas valve they are changing?



    Has anyone soaped the orifices when this testing is being done to see if they bubble? I would also soap the gas valve to see if there are any bubbles.
  • lchmb
    lchmb Member Posts: 2,997
    edited January 2012
    Hi Tim.

    As I said, this is not something i have been involved in, just being asked for thoughts. They are performing a pressure test at the second stage regulator with the appliance off. With a new valve, a test was taken and no leak indicated. After running the appliance for approximately 15 minutes (flow 11") they shut the unit off (lockup 11.8") the shut the second stage off and dropped the pressure to 10" (approximately) and it would not hold for 3 minutes. They did soap the orifice's and they were bubbling. There has been no high pressure test of the system (3lb or 5lb) and as I said, the tank was replaced and all line's leading up to the unit.....sorry was out chasing no heat calls or I would have answered sooner...

    I hope to meet with them tomorrow to get one of the valves to test it myself and see if I can find something going on...will let you know what model valve it is then..:)
  • Empire_2
    Empire_2 Member Posts: 2,343
    I'm currious....

    The orifices on the manifold should not be bubbling when soaped as you know.  The Q: is why?  I wonder if somehow  damage to the diaphragm on the GV is occurring somehow at some point?  I know it's not in your site, waiting to see what you find....From the outside tanks I look for 12:wc to the house, 10.5 fire rate on furnace.  Has anyone checked to see if the spring for GV reg. is actually Propane??? 



    Mike T.
  • Bob Harper
    Bob Harper Member Posts: 882
    leaks

    Gas cocks are rate either 3 or 5 psi depending upon mfr. However, you NEVER test at pressures over 14 wci past a gas cock with an appliance connected. Gas combination valves are allowed trace gas leakage by ANSI of 200cc/hr through the seals of the valve and 235cc/hr through the main operator leaking to the burner both at 3/4psi or 21 wci. You can check to see if gas is still leaking out of the main operator or the regulator vent when the burner is shut off and you're leak testing. Has anyone tested the vent on the second stage regulator to see if it is 'leaking' constantly. If so, you have a blown diaphragm. Note that lower pressure leak tests are more accurate than high pressure tests.A water manometer or bubble meter is what is used in the lab. Also check your hoses and connections on your manometer. Use a commercial soap soln. such as Big Blu with know characteristics and give it time.
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