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low water cutoff controls - redundancy?

elfieelfie Member Posts: 264
here are two lwco controls

why are there two?

seems that when ball valves are opened (below the cutoff devices), the water flow comes from boiler and not pushed down thru the LWCO devices - is this ok?

is one used for high water cutoff?


  • SteamheadSteamhead Member Posts: 11,323
    On a boiler that size

    Code requires two LWCOs and two pressure controls. One of each is a manual-reset unit that trips if the first control fails.

    On that boiler, the larger LWCO is probably also a boiler-feed pump control. the smaller should have the manual-reset feature.
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  • JohnWayneJohnWayne Member Posts: 27
    The piping is correct

    That piping is correct.   As long as you have a head of steam on the boiler when you open the ball valves it will push through the LWCO.  If you don't feel like it is passing through you may want to open them up and make sure they are not clogged with mud.  Don't forget to check the piping as well.  The taller of your two LWCO has the three test cocks on the back.  You can use these to check the water level in the boiler if your sight glass (gauge glass) ever is to dirty to see.  The bottom valve should be straight water, the middle should be a combination of steam and water, and the top should be straight steam. 

    What Steamhead said about the code is correct as well.  One should have a manual reset on it.

    Also I noticed the gauges and pressure controls are straight piped into the header up top.  You should install siphon tubes (pigtails) to help prolong their life.  These will help create a buffer between the steam and the controls.
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