steam riser untrapped and connected to wet and dry

Christian Egli

Now I'm running out of imagination. I'll have to start making up things.

When you go look at your mystery location again, look at it from these three angles.

First, how does steam get there. Pay careful attention at every point where the lines hit a low stop. An exit for condensate should be provided.

Secondly, look for how condensate goes away and how steam is prevented from traveling along a wet or dry return.

Thirdly, and there is a third wheel in this marriage, look at how air is shown the way out. The air must be removed for a harmonious relationship to develop. It can get out through a vent, a vacuum line, or a dry return, but not a wet return.

Pat Linhart's Field Guide is a nice book about these relationships.

Your picture shows maybe there was something feeding off of that drip at some point in the past. The drip and cap is not original to the rest of the piping. Do you have any idea of what was there before?

Two things worry me at this point.

1 - With a wet return at the bottom and two confusing steam lines, where does the air get out?

2 - You mentioned earlier the building had converted from wet to dry returns. Is this now a converted return too? If so, then what prevents steam from going down where only condensate and air should go?

So, Steamhead, you often go on adventurous trips around the beltways? You know them enough to know their number, wow. I once drove as far as I could east on the I-70 just because I thought it would be sooo exciting, well, it ended like a steam main with plugged air vents: it becomes a park and ride lot, from which I promptly got lost, luckily Baltimore is a nice city.

Should have taken the beltway, should have paid attention to that sign:

End I-70

joe barone

steam main untrapped and connected to wet and dry

I'm working in the basement of an eighty year old building with a two-pipe vacuum system (whose vacuum pump hasn't worked in years). All of the steam risers (there are about 45) are dripped and trapped normally into a (an originally) wet return line except for one. This riser is not trapped at all, but is connected both to the wet return near the floor and the dry (return riser) return higher up the wall. I cannot make sense out of this arrangement in this context. Can anyone help?

Thanks very much.

Christian Egli

Special one way pipes for steam, condensate and vacuum

This last riser is a steam riser? for sure? or is it just full of steam leaking trough a faulty trap?

Return risers ending up differentiated between wet water return and dry vent return is common.

Was there ever a steam engine in this building?

There were setups where there were two return systems running together, one at atmospheric and one under vacuum, and crossover links (with traps) between them.

In your description it doesn't make sense that a live steam line would be piped directly into a return. These wet and dry return, are they the exact same as the ones that serve the 44 other risers. Is it possible that these special returns lead to a crossover trap that links them to the rest of the returns, the main returns, if so, then it's all ok.

For a time, feedwater pre-heaters were popular. These made a final use of the return condensate before returning it further. Maybe these special returns led to such a gadget that could use whatever remaining steam came down this last riser.

If steam from this last riser is causing problems in the return, I would suggest installing a common thermostatic trap as a crossover.

One last thought.

On vacuum systems there is a crossover link somewhere that connects the mains directly into the return, via a check valve. This is only to guarantee that the return vacuum is always deeper sucking than a vacuum in the steam main and the boiler.

If so, it still does not harm this anti-deeper vacuum crossover line to have a thermostatic trap along it. Check valves are not always foolproof.

Look for a check valve somewhere on this dry line. They can look just like a coupling. The old wet, now dry line might still need a f&t trap.

Is this a Webster system?

Boy, more questions than answers! Very helpful.

joe barone

After reading Mr. Egli's excellent suggestions, for which I am very grateful, I spent more time tracing the lines from this aberrant riser. Large sections of the paths of the various pipes are obscured by banks of tightly packed gas lines, so this is not easy. In any case, it seems that what I thought was a dry return line actually traces back, after some distance, to another steam main (we are dealing here with just a single boiler). So if we look at the riser from the top down, we have connected a steam main (close by), then just below it another steam main connection (long, main far away), and then a drop to the "wet" return. I also forgot to mention yesterday that the connection to the wet return is via a horizontal 1 1/2" pipe, with the drop to the wet return teed off; this pipe then proceeds some six or eight feet and reconnects back to the second pipe (the second steam main connection). I was unable to find a check valve anywhere, but, as I said, some areas are hard to see.
So it is quite likely that Mr. Egli is correct, though I still can't prove it.
Further ideas would be most welcome.

Christian Egli

The David Letterman beltway

Aww, I was on a roll

Anyway, I am posting a picture of what an end of steam line can look like. You'll notice the wet return and the dry return. You'll find a thermostatic trap on the highest point in the dry return. Therefore, it is not always obvious to see the trap. The same goes for a check valve which should be level with all the others in the wet return.

But,

What you seem to have now, is simply an obstacle skipping piping arrangement. Like you would have for a steam main needing to cross a doorway at chest height.

To do that, you simply create a big beltway all around the doorway, going north and going south of the obstruction. Just like we do when avoiding the drive through a congested downtown. Traffic finds its way around, the condensate piles into a jam on the lower portion of the beltway while the smarter steam finds the open passage provided by the upper piping.

Traveling horizontally on the I-70 through either Columbus or Indianapolis is a perfect example of this. Both cities have totally circumventing beltways. You'll remember David Letterman wanted the one around Indianapolis named after him.

No traps needed for this set up.

Steamhead (in transit)

Ahhh, but

to my knowledge they don't call them "beltways" even though they are, just I-270 or I-465. When I'm in those cities and mention "the beltway" I get blank stares........

Joe, can you post a pic of this setup? I think Christian is right, it's either a way to get around an obstruction of some sort or it might be a "rise and drip" to bring the steam main to a higher elevation without trapping condensate in it. But I've seen some unique piping arrangements especially in Webster systems, so it would help to see it.

Also, where are you located?

joe barone

picture and more details

Once again, thanks very much for the help. I attach a picture. The upper horizontal pipe, barely visible, attaches to a steam main nearby which also serves risers on either side of it and others. The second horizontal pipe is the one that runs some 35 feet back toward the boiler and ultimately attaches to another steam main much closer to the boiler. The lowest pipe, as is clear from the photo, tees off down to the wet return, continues briefly, and then turns 90 degrees to follow the second pipe toward the boiler. After six or eight feet (on the other side of the wall, so not visible), it attaches back to this second pipe.

The building is located in New York City (Manhattan). There is absolutely no issue of obstruction: no doorways, pits, humps, or anything like that are traversed by any of the pipes involved. All the pipes are located along one wall of the basement, which in the area is divided up into a number of rooms (storage, gas meters, workshop, etc.). This means, of course, that the pipes must pass through walls, but in all cases suitable holes have been broken through for that purpose.

I am very grateful to the responders for their help.

Joe

Ed_33

'Steam pipe untrapped and connected to wet and dry'

The picture shown is a common configuration on the end of mains on vacuum systems. To 'vent' air from mains on vacuum systems there is a trapped line connecting the main to the vacuum return. At the same time the bottom tee is dripped to a wet return, which should gravity feed back to boiler or boiler feed tank.

joe barone

further details

All three responders seem to feel that this is a steam main to vacuum "crossover", and I have no reason to doubt their opinions. I went and bought a better flashlight and studied everything again. There still seem to be a few peculiarities:
(1) This riser is not at the end of any main.
(2) I absolutely cannot find any trap of any kind connected to this riser or even vaguely associated with it.
(3) The mysterious second pipe seems to trace back to a steam main, as I have noted, and so there really isn't any crossover.
The only conclusion I can reach is that my tracing must be wrong. I will try to get a younger person to trace it within the next few days and report the results here.

Thanks again to all responders - Joe

Steamhead (in transit)

Actually the sign says

"I-70 Ends at I-695". If you go the other way (westbound) there's a sign with mileages to St. Louis, Denver, and the west end of I-70 at Cove Fort, Utah. I have family in Indianapolis, that's why I've been out there as often as I have.

Joe, that might just be a drip, clearing condensate from the mains. Have you found any manufacturer's info on the system's original hardware such as traps, valves, vac pump etc? This may help us identify it, especially that strange piping arrangement.

Steam Bunny

Any possibility the bldg might be a wee bit older than 80 years?

If so & you still can't find any mysterious gizmos down in the basement, have you taken a look at the radiators to see if their traps hold any clues? If there's no visible writing, a mirror would help to confirm nothing's on the back side either.

Just a shot in the dark from a 1 system home owner.

joe barone

final resolution (sort of)

I found a younger person to trace the configuration. Unfortunately, it appears that I was correct. So this is what we have decided. As one of the responders surmised, we think that the second steam main (the second pipe definitely goes back to a steam main) was connected because not enough steam was getting through from the top one, which is relatively close to the end of a long run. The extra connection from the wet return drip back to the second main was to remove condensate accumulation in the (new) branch (we think). The whole arrangement was untrapped because it was done when the wet return was still wet. After the boiler feed tank was added and the return became dry (and all the other risers were trapped) this one was left alone because nobody involved at the time understood what was going on.

Our solution: repipe the lowest section and make a simple (F&T) trapped drip to the wet (now dry) return. We'll leave the double steam connection for now, and keep a close eye on the whole thing this winter.

Many thanks again to all who responded. Joe