boilers flooding

tekmar

have 3 -60hp low pressure steam boilers used for heat and hot water ,one lead, next one lag and next one lag ,one boiler can carry the load ,two others for backup just in case , the two lag boilers are constantly flooding ,only one boiler has a non return valve,connected to a common header ,after maybe two days the two lag boilers start flooding ,should there be non return valves on all boilers or any idea on how to stop the flooding   thanks

jpf321

maybe ..

maybe study the pictures of boilerpro here: http://www.heatinghelp.com/forum-thread/128612/This-years-Steamers .. i know that he has several twin systems in ..



when you say "non-return" valve .. do you mean a one-way-check-valve?

perhaps they are flooding from header connection rather than from return connection? could condensate/foam/surge be pulling water up the live header and dropping into the other units? do you have iso valves on the individual boiler risers, this would be a way to test.



i'm also trying to be clever and see how pressure differences may affect things .. i closed the bottom valve on my gauge glass last week and forgot to reopen it .. the next time i looked, the water was nearly at the top of the glass .. HOWEVER, this was a false reading .. once I opened the bottom valve on gauge glass again, the water bounced back down .. this may have been the case of the condensation from the open top end (steam exposed end) condensed in the glass and has nowhere to go but fill up the glass ..



maybe that's what's happening on a larger scale on your side .. you are sending steam into the backup boilers through the joint header .. and it's condensing there with no way out...i would think that if you have offline boilers in a shared connection condition, you would need to have installed iso valves to prevent this problem...otherwise the steam is entering the backup boilers and condensing with no way out.