Two pipe steam question

adambuild

Hi Wallies,

I quickly looked at the two pipe steam system of my friend today. The rads are taking a long time to heat up and some were still cold with the boiler having been on for over an hour. I'm very experienced troubleshooting one pipe steam, but almost never deal with two pipe steam. Can I assume that the first places to look are the individual steam traps as well as the main vents? Any other quick advice?



Thanks as always, Adam

Rod

Probably a Bad Trap

Hi Adam- Sounds like a bad trap or traps and steam is then getting in to the dry return which then cancels out the pressure differential resulting in no steam flow into the radiators. Does the system have an F&T or cross over trap on the end of the steam main? 

Finding the bad trap(s) can be a bit of a problem. You can shut off all the radiators and then open them one at a time to check them. The one(s) that get an immediate hot return pipe means that the trap isn't closing properly when steam reaches it.  (Be Careful! Steam Pipes are HOT!)

Santa brought me a Ryobi infrared thermometer last Christmas Model # RP4030 available at Home Depot for about $70. Best invention since sliced bread! Great for checking traps!. Take the inlet pipe temperature and then the outlet pipe temperature and then compare the two. Small temperature differential equals a bad trap. 15 -20 degree differential equals a good trap.



There are rebuild parts available for most traps.

Here are some sources for you:

Source for complete traps & parts:

State Supply

http://www.statesupply.com/steamTraps.jsp



Rebuild parts for Steam Traps (Thermostatic,  F&T)

Barnes & Jones

http://www.barnesandjones.com/



Tunstall

http://www.tunstall-inc.com/tunstallsteam.html



- Rod

Jamie Hall

And don't forget

to check the main vent(s) -- if they aren't opening, you could get that sort of problem.



Which, if they were ever seriously overpressured, is a distinct possibility.



You may or may not be able to feel air moving out of the main vents -- sometimes you can, sometimes you can't.  If you're feeling greatly daring, you can simply take one of them off and see if that makes a difference -- just keep in mind when you do, that when steam does get to the vent, a) it's going to be very very very hot indeed and b) there's going to be a lot of it.  Don't try to put the vent back at that point!  A better plan is to use a known good vent and swap it in in place of one of the old ones and see what happens...