Strange steam "equalizer"

Gary Elovitz

Hi all -



I saw something in the field that I can't figure out.  The system is a one-pipe steam system with a wet return that runs along the floor.  The boiler is a Weil 1188 (bout 3,000 MBH).  As you can see in the attached simplified sketch, there is a 1" "equalizer" line that connects from the side of the steam header (so it takes steam, not condensate) to the wet return.  (This is in addition to the normal equalizer line and Hartford Loop.)  There is a big (1-1/2") trap just below this 1" line, and the trap dumps to the boiler feed tank, which pumps into the boiler.  It is the only trap in the system, and it is below the boiler's water line.  I can't see what this 1" line is for, unless it is to allow the boiler to run at a pressure above 1 psi - i.e., to prevent boiler pressure from pushing through the return, through the feed tank, and out the feed tank vent.   Any ideas?  When the boiler is replaced, do we keep the 1" equalizer and trap, or eliminate them?



Thanks!

Dave in QCA

Alternating Receiver, perhaps?

A picture would do wonders here...    It sounds like some of the old equipment was not removed when an older boiler was replaced with a boiler and a condensate receiver.

An Alternating Receiver does the same job as the receiver tank, without the need of a pump to put the water back in the boiler.  There should be 4 connections, or perhaps 3, if the condensade line coming in and the boiler feed lines are fitted with  check valves.  The 2 top connections consist of 1 vent and 1 steam connection.  The bottom connection is for condensate.  As the condensate comes back from the system, it rises through the bottom port into the body of the receiver.  Air is exhausted throug the vent, the steam connection is closed.  As the the receiver fills, a float mechanism causes the vent to close and the steam connection to open.  Now the receiver is at the same pressure as the boiler, and since it is at a higher elevation than the boiler, the condensate runs out, and into the boiler.  Check valves prevent the condensate from flowing backward to the system, and also prevent the boiler water from flowing backward into the receiver when the receiver is at atmospheric pressure.  

Look at the low pressure diagram on page 2 of the Sarco Alternating Receiver brochure.  I found it posted on this fantasic site!  Here is the link,  http://www.heatinghelp.com/files/articles/1323/58.pdf 

Not sure if this is what you have going on, but it sure sounds like it.

gerry gill

if the wet return bypasses the feed tank

as the drawing suggests, when its time to do some replacement or repiping i would just install an equalized reservoir tank in the wet return to hold extra water for the boiler, and thats only if it was found that there wasn;t enough water for the steaming process..in the current configuration the line you question makes no sense to me either..

Steamhead

Is the trap

higher than the boiler's water line?



If so, what you have is a False Water Line. It is designed to keep the standing water in the wet returns higher than the boiler, so water will fill the returns up to a point and keep steam from going places it shouldn't. The waterline of the existing boiler is probably lower than that of the original, and the FWL makes up the difference.

Charlie from wmass

Gary was this near Boston?

Seems to be a few "old" steam guys adding those traps out there. They say they need them when they add the pumps to keep the system from banging and the receiver tank from flooding. I think they need new returns and the3y are doing this to postpone changing out the half clogged returns. But since it "works: no one wants to fix it.

Gary Elovitz

Thanks!

Thanks for all of the input.  The building is near Boston, and the trap is below the water-line.  I'm still scratching my head, but I appreciate all of your suggestions.