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Gauge glass question

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HNewlen
HNewlen Member Posts: 1
in Strictly Steam
We have an old (converted from coal to gas) furnace, single pipe. About 2 weeks ago I noticed a whistling/hissing which came from where the gauge glass goes into the metal nut above it. Today steam is noticeably escaping when the furnace runs. The furnace has been running significantly more as the temperature has been colder the past couple of days than we've been - in the teens - and tomorrow is expected to be single digit. Is this a concern?

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  • BobC
    BobC Member Posts: 5,478
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    Is the pressure any higher than normal? If it is your pigtail may need to be cleaned.

    The rubber gauge glass washer is probably deteriorating and my have to be replaced. You can try tightening the bonnet nut to see if that stops the steam leak. Be gentle, you don't want to break anything.

    If tightening doesn't work you will have to remove the gauge glass and clean off both the top and bottom fittings and install new rubber washers. The boiler has to be off and the top and bottom valves have to be closed when doing this. I would have a new gauge glass on hand because you might break the old one.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
    Answerman
  • Fred
    Fred Member Posts: 8,542
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    After a number of years, the bottom side of the gauge glass can have some erosion. I would replace both the rubber washers (top and bottom) and replace the glass as well.
  • JUGHNE
    JUGHNE Member Posts: 11,062
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    Before trying to tighten the glass nuts, I would be sure the isolation valves for the sight glass will close. It may take a little force to close them if not moved for years. I would get them loose and then exercise them in out as you close them. If cold weather you could close them and just crack them open for your inspection. Make sure your low water cut off device(s) work.....they should shut down the fire when tested or activated.

    When warmer weather arrives then you could attack the sight glass washers. There is often a thin brass ring under the nut and then the rubber washers. The ring keeps the nut from distorting the rubbers.

    Often sight glasses have to be cut to length.

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