Feedwater tank, but no traps...

Mike_Sheppard

Building in NW DC. Built in 1910. Standard one pipe system piped back in the coal days. Two Long mains wrap around the basement. One main has three other small mains that feed off of it. Mains end at the other side of the building right next to each other. Old wet returns were abandoned and above ground lines were run. Boiler was replaced. Feedwater tank added. No traps added to the ends of the mains or returns from the 3 small mains on the south side of the building.

They’re lucky they run their boiler at 10 ounces and there was enough of a water seal from the condensate dropping down and going back up to the tank to stop steam from blowing out of their tank.

Two of the three small mains are now dry returns whereas they used to be wet returns. One main short circuits to the other through the return.

The ends of the mains are tied together with no trap. One main short circuits to the other.

One main is about 200 feet long and the other is 150. Both are vented with a single Gorton #2. Only other vents are on the radiators.

I need to refresh myself with Dan’s book for sizing traps in a one pipe system. It’s parallel flow so the ends of the mains are going to have to handle the condensate. Also need to size air vents for the ends of the mains.

My current main question is, is it alright to use a loop seal rather than an F&T in a situation like this?

Mike_Sheppard

Pictures are coming. Every time I try to upload it gives me an error.

Jamie Hall

Why not use a loop seal? Well... one thing. Make sure that the pressure is low enough and stays that way to avoid blowing the seal.

JUGHNE

I am trying to picture this in my mind.
Just a crazy idea here from the less experienced....
If all the dry returns are hanging high, is it feasible to raise the feeder tank up to create more of a water seal?
Then add massive venting on the end of mains or dry returns.
To avoid any F&T's.

Steamhead

What you need is a False Water Line. This is covered in chapter 3 of Lost Art.

Mike_Sheppard

Two of the little mains that come off the large main are dry returns (now). The ends of mains and the third little main are all wet. They drop down to the floor, run down the hallway, drop under the slab at the boiler room, run over to where the tank is and rise back up out of the slab into the tank.

I will look into the false water line.

Mike_Sheppard

Will definitely have to change the end of main returns. They come off and tie together directly below the mains then drop down to the wet return. Definitely above the old water line.

Mike_Sheppard

Here you can see the ends of the mains tie together in the ceiling, well above any possible water line.

Steamhead

Mike_Sheppard said:

Here you can see the ends of the mains tie together in the ceiling, well above any possible water line.

Looks like that was done much later then when the system was installed.

Mike_Sheppard

> @Steamhead said:
> Here you can see the ends of the mains tie together in the ceiling, well above any possible water line.
>
> Looks like that was done much later then when the system was installed.

That’s what I was assuming. That will have to be corrected either way.

Thank you for reminding me about the false water line, Steamhead.

EBEBRATT-Ed

If you put traps on each return I would size them base on connected EDR + weight of pipe and fittings x a 2-1 safety factor.

If you use false water lines or loop seals I would think you need one on every return. If the returns are tied together above the false wl /seal steam will back up into the other returns. Would have to vent the inlets of FWL/seal

Mike_Sheppard

Got it. Read this a long time ago and have never seen it used before. I think this will solve the main problem they have. Then the ends of the two mains need to be re-configured to connect below the water line.

One main is 200 feet of 3”
So 10.6 cubic feet of air

The other main is 150 feet of 3”
So 7.95 cubic feet of air

The two mains each have a 1/2 inch tap that was added at the ends with main vents. Looks like changing the 150 foot main to a 3/4” tap and the 200 foot main to a 1 inch tap would allow me to vent them both at approximately the maximum venting capacity for open connections and have them fill with steam at about the same time.

I still need to measure those other 3 small mains coming off the 200 foot main. Each of the three has a single Hoffman 40 at the end. Unfortunately two of them are in a crawl space under the building. So that will be fun..

Mike_Sheppard

> @EBEBRATT-Ed said:
> If you put traps on each return I would size them base on connected EDR + weight of pipe and fittings x a 2-1 safety factor.
>
> If you use false water lines or loop seals I would think you need one on every return. If the returns are tied together above the false wl /seal steam will back up into the other returns. Would have to vent the inlets of FWL/seal

The ends of the two mains tie together above the water line. Like Steamhead said, looking at the picture it doesn’t look original. If I re-do that and make them tie together below the water line (of a false water line) then that will be solved. The other two small mains that tie together above the current water line will be covered once again by installing a false water line. I think the false water line and fixing the ends of the two mains will solve that problem.

Mike_Sheppard

Here’s a picture of what I am talking about with the ends of the mains.

This is almost exactly what their system looked like before the new boiler and feed tank where installed however long ago.

BUT, where I circled in red, someone at some point in the past tied the ends of the mains together almost right at the top, well above any possible water line they had. If I do a false water line I still need to separate those and make sure they connect below the water line.