Steam boiler 2 pipe system questions

JoshP

Traps

Thanks for the help all. Sounds like a plan. I will get to replacing the elements in the traps.

I pulled apart the one I removed already and found it pretty simple. Pretty similar to a carburetor needle and seat. I restore cars on the side so I have the tools and it won't be difficult.

Again thanks. Once I finish I will repost the results.

Jamie Hall

On vapour systems and vents

The only one I can speak to from hands on experience is the Hoffmann Equipped system -- but many others had similar quirks.



In the Horrmann Equipped system, for example, one of the objectives was to avoid having the water pushed out of the boiler into the returns by excess pressure in the boiler (excess being defined, for these puppies, as anything over about 8 ounces!).  One has to remember that when many of these were installed, you were heating with coal, not oil or gas, and despite some really interesting contraptions to control the draught over the fire it was quite possible for the pressure to rise too much -- no vapourstats in those days!  So what they did was create an arrangement where, if the pressure got too high, the returns would be pressurized as well -- equalising things and getting the water back in the boiler (and, not trivially, taking the pressure off the traps).  The Hoffmann Equipped does this with the Differential Loop, which is a most ingenious arrangement with no moving parts. There is a kind of U trap arrangement, about 18 inches deep, with boiler pressure on one side and the dry return on the other (if there is more than one dry return, they are all hooked together at this point).  At the top of the assembly, where the dry return enters, is where the main vents are located.  If the pressure gets too high, it pops the water out of the trap arrangement, and steam zips up and hits the main vents, which closes them -- and puts boiler pressure on the dry returns (but without steam actually getting in there; the returns stay cool).  This allows the water to get back into the boiler from the wet returns.  The U trap arrangement -- the Differential Loop -- promptly refills with condensate coming back in the dry return and closes the steam flow and, as soon as some condensation occurs and things cool a bit, the main  vents open again and everything is back to normal.



As I say, simple and ingenious.



The steam mains are vented at the ends with crossover traps -- which are just radiator traps (sometimes one size larger) which are piped above the steam main and over and down into the ends of the dry returns, so that they never see condensate -- just air (condensate is handled by drips to wet returns).  They flow, of course, a lot more air than a vent does, even a big one.  The dry returns tend to be pretty generously sized, to reduce any pressure drop to a minimum.



That help any?

MTC

Yeah, I think I get the basics of the system...

will have to do a little more research on it. Diagrams help me visualize this kind of thing, but your description got me at least most of the way there. Thanks for the edumacation

Dennis Foley

Fix the boiler piping

If this is truly a 2 pipe counter-flow, then that boiler piping is probably causing most of the problems. Yes, there may be bad traps, but in my experience traps mostly fail in the open position. In my opinion, there is a significant amount of water being drawn up into the mains. A counter-flow should be piped so that the feed from the boiler is heading down into the equalizer, with the supplies to the system coming off that horizontally. I would have to think about how to do that with 2 supply loops, but I know from experience that it works on one supply loop, which is how most of the counter-flows I've done are installed. I am pretty sure from the pictures that the header piping is undersized, although we would really need to know the EDR of the rads to determine pipe sizing. The importance of boiler piping should not be minimized. It's the source of most of the problems that I find here in Boston. Fix the boiler and then it's just a matter of fixing individual radiators.

Rod

Counterflow Boiler Piping

Hi- Attached is a pdf on counterflow boiler piping and some pictures of really nice  counterflow boiler piping done by Steve Gronski, a Rhode Island steam pro.

- Rod

JoshP

I'm back

Hi guys

I'm going to start a new thread with my results and a couple more questions. This thread has gotten too long. I will label it "steam 2 pipe phase 2"