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Posted by GeneratorGrrl on April 04, 2005 at 14:49:09:
At our compost bunker, I've got a small low-pressure hot-water boiler system, running ethylene glycol at 85C in a closed loop. Air is entering the system, causing foaming and cavitation of the pump. The air seems to be entering through the bleeder valves, which is the opposite of what an air bleeder is supposed to do :) What appears to be happening is that as the liquid cools and shrinks in the system (which does have a cushion expansion tank), the lowering pressure is causing the bleeder valve to open, sometimes shooting liquid out of it.
I've never seen this problem on any of the straight-water systems I've worked on in the past, only on this glycol system. Is there a type of air bleeder valve specifically for glycol systems? When the glycol spurts out, it does dry to a sticky residue and it occurs to me that this could clog a normal bleeder valve and cause it to stick open. Is there a way to overcome this problem?
Any thoughts or suggestions are quite welcome.
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