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This weeks case, The case of the flooded lag boiler and bonus videos added

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RayWohlfarth
RayWohlfarth Member Posts: 1,518
This weeks case, The case of the flooded lag boiler is about a school with two low pressure steam boilers, each set at 2 psi. The lead or primary boiler failed and the lag or idle boiler didnt start. When I arrived, the lag boiler had a pressure reading of 3 psi and the pipes were cold. What happened here and how could it be resolved? As usual, I will hold my comments until Friday at 6am EST when the video is released.

As an added bonus, I uploaded two new videos for help sizing combustion air for a boiler room The first video is using wall openings and how to meet the code. https://youtube.com/watch?v=NmeIZ-VzyQA

The second video is using other methods for determining the combustion air. This includes indoor air, mechanical ventilation, and direct connected combustion air like on condensing furnaces. https://youtube.com/watch?v=Ss18q3pWfvE

Hope you enjoy them
Ray


Ray Wohlfarth
Boiler Lessons

Comments

  • ratio
    ratio Member Posts: 3,652
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    The boilers weren't properly twinned & the lag boiler was filled with water.
    ethicalpaul
  • ethicalpaul
    ethicalpaul Member Posts: 5,735
    edited May 2023
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    Not just the boiler, but all the piping above it, right up to the main I bet. The solution is to remove the lag boiler, it probably wasn't needed anyway. And as shown by this case, if and when it might actually be needed, it's been so long since it's run that something is probably failed anyway and it won't start.
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el
  • mattmia2
    mattmia2 Member Posts: 9,747
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    Not just the boiler, but all the piping above it, right up to the main I bet. The solution is to remove the lag boiler, it probably wasn't needed anyway. And as shown by this case, if and when it might actually be needed, it's been so long since it's run that something is probably failed anyway and it won't start.

    Or it works if the lead boiler is already firing.

    This sounds like a check valve somewhere keeping the condensate from the system from leaving the non-firing boiler.
    GGross
  • retiredguy
    retiredguy Member Posts: 915
    edited May 2023
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    This is a case for liquid drainers or traps mounted on the water tree piping between the normal water line and the top of the sight glass. It was flooded from setting idle and the steam in the boiler above the water line condensing. By the way, attempting to drain that flooded boiler could lead to a disaster if done incorrectly. I have seen many cracked sections on cast iron boilers from that same condition. I once was present when that was tried by the "chief engineer" on a cold, flooded, Keeler lag boiler at a hospital running 100 PSIG steam. I lost many years that day. Boy, was I scared.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,622
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    @retiredguy beat me to the punch and has this right in my opinion. Lag boilers on steam will always fill up unless equipped with an overflow trap. The condensed water in the lag boiler may build enough pressure to trip the pressure control

    That is one reason Preferred Utilities made an alternating lead lag control for steam.
  • RayWohlfarth
    RayWohlfarth Member Posts: 1,518
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    The issue with this project was the boilers did not have high level spill traps. ASME code recommends installing them when using two or more steam boilers. The traps are installed about two inches above the normal water line. It keeps the lag boiler from flooding. In this boiler room, the steam takeoff rose about twenty feet. The weight of the water column fooled the lag boiler into thinking it was up to pressure. In the old days when steam boilers had large steam chests, they used to use an equalizing pipe between the boilers and the condensate was fed into that. The new boilers cannot be done that way now due to the smaller boilers.

    @EBEBRATT-Ed Someone just sent me a lead lag panel he used to alternate the steam boilers every few hours. I thought it was interesting.

    Here is the link for this weeks videohttps://youtube.com/watch?v=3VleZMGdm4k


    Ray Wohlfarth
    Boiler Lessons
  • PC7060
    PC7060 Member Posts: 1,175
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    glad your voice is back, Ray!
  • retiredguy
    retiredguy Member Posts: 915
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    Wow ray, a 350 smith. I probably was in that boiler room a few times but I can't guess the name of the school.
  • RayWohlfarth
    RayWohlfarth Member Posts: 1,518
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    Thanks @PC7060 me too
    @retiredguy figured you would like that
    Ray Wohlfarth
    Boiler Lessons
  • JUGHNE
    JUGHNE Member Posts: 11,075
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    So the lag boiler had probably almost never run since install.

    Apparently no one at the building thought too exercise it every month or two, no surprise to that.

    And never checked the LWCO's on the lag boiler.
  • RayWohlfarth
    RayWohlfarth Member Posts: 1,518
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    @JUGHNE The system was set up to change lead boilers once a year. The controls were checked before the heating season When this happened, it was toward the end of winter although it was still cold. The onsite people apparently did nothing as fas as daily or weekly maintenance
    Ray Wohlfarth
    Boiler Lessons