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Posted by Jerry Moore on November 24, 2004 at 11:59:38:
In Reply to: Re: water column and water level controller posted by Steaman on October 17, 2004 at 18:22:05:
: : : Recently replaced controller (McDonnell-Miller
: : : 150s) and seems to be extremely sensitive
: : : to water oscillation when feed water pump
: : : comes on causing numerous low water
: : : shutdowns. Have increased blowdown in that
: : : suspected TDS problems but indications are
: : : that has not significantly increased. Should
: : : I suspect my water column equalization lines?
: : : Any other obvious things I am overlooking?
: : IF this is an adjustable style that turns the pump on & off they really take a lot of tweaking to get things set up right.
The contractor that i work for just got finished installing 11 wiel-mclain boilers in 4 schools in NJ and we had the same problem on all 11 boilers. The boilers would fire for approx. 10 min and the water would drop right out of the sight glass and never to return. The condensate pumps were 3 times the size of the boil rate of the boilers. 25gpm pumps for 9gpm boilers. We have had countless meetings with the GC and the pump manuf. and the owners. We finnaly fugured out that the piping configuration in the header was piped so that the steam supply leaving the boiler header going to the common header was at the opposite side of the equalizer line. With the high velocity of the steam it caused a vacumme at the back of the header causing a suction effect on the water in the equalizer which actually SUCKED all the water out of the boiler and making them go out on low water. the rate of water leaving the boiler far exceeded the rate of flow from the condensate pumps.
I would take a VERY close look a the piping configuration and compare it to the manuf. piping schematics.
I cant take credit for finding the problem (unfortunatly) it goes to a boiler/welder that came to look at the problem.
Jerry