FT Traps

scott75

There are returns after the FT traps that go back to the boiler. There is an air vent there, as well as a vacuum breaker valve. After you clean out the pig tail, is it okay to put it back in service without water in the pig tail and just let condensation form from the steam, or should you put water in it before firing the boiler again? What do you use to clean the out the FT traps? Do you just scrape out the rust and scale or do you use a chemical? I need to see a new one to see how it looks so I have something to aspire to.

If all the rads were hot, and burner was cycling off the pressurtrol, and stat wasn't keeping up, is it likely the air valve on the return main was bad? I am not familiar at all with vapor systems. What would be the purpose of the vacuum breaker valve?

scott75

Steam- FT Traps

Hi guys. I need a little help. I looked at a 1930's residential steam system today and I don't see many. This was one pipe with a separate return line. It had 2 FT traps, one at the end of each horizontal main. The burner was cyclying properly off the pressurtrol. When I arrived pressure guage read 2.5psi, burner not on. Pressurtrol dialed down all the way. Stat was calling, but system was not keeping up. Rads were hot all the way accross, except those where the adjustable air vent was dialed down, those weren't as hot accross as the others, but felt consistent. I took apart the FT traps, and cleaned the junk out. Are these meant to be cleaned? What is the expected life of FT trap? If it's working properly, should the return pipe after the trap get hot or not? I would think not because then it would be letting steam through when it shouldn't. When I put the FT traps back together, they drip water now. Can the gaskett be replaced? I then dialed the pressurtrol up a hair to get the burner to kick on, the pressurtrol never turned it off. The pressure guage was reading 8.5psi and the relief valve was going off. I'm thinking it needs a new pressure guage, pressuretrol, and 2 FT traps. They all seem suspect. This is a heavy bill the customer and I would rather not do guess work. I did clean the pigtail. It didn't have any crud in it but it was full of clean water. Is it okay to have water in the pigtail? I've never seen one piped like this. It was piped directly off of the McDonnell and Miller float style LWCO. The pressure guage was piped completely separate, not tee'd off the pressurtrol like I usually see. Sorry for the long post. Any help would be appreciated.

Scott

Al Letellier_9

F/t traps

Are you sure it was a single pipe steam? If so, why the F&T traps at the end of the mains? You can buy rebuild kits for the traps that will include a new gasket. In a pinch use some Permatex Form-a-gasket to fix the leak.
Try replacing the pressure gauge first...they are notoriously bad on steam...it just eats them up

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Tom R.

Trapped

Yes, you should clean & inspect traps. Replace what's needed and install scale traps in the line ahead of them. For a quick check of suspect traps, they sell a crayon to mark the outlet with. They come in different temperatures. If it melts, the trap is leaking. Trap body should last forever, unless you freeze it. The pigtail is supposed to have water in it - steam condenses in there and protects the device from heat. If the pressuretrol is piped from the LWCO, check the LWCO for mud inside or blocked connections before replacing the control.

Christian Egli_2

One question raises another

But then there are radiator air vents too.

What brand are the two F&T ? They may not be necessary at all. Where does air escape to the atmosphere from the returns piped after the F&T?

Otherwise, if these F&T are not the common modern brands, it is possible these could be what used to be called air eliminators (but I doubt it since you have radiator air vents)

Is it possible the radiator air vents are an aftertought? Are there no radiator traps at all? maybe some type of seal trap?

Figure all this out first, because rather than a pressostat your system may need a vaporstat. It seems clear your current one is not 100%. There is no reason at all to be up at 8.5 PSI.

The Lost Art should give you identifying pictures.

John S.

I agree with Al...

Is this one-pipe or two-pipe steam? What does the 'seperate return line' consist of?

How many pipes connected to the radiators? Air vents on them or traps?

Sounds like maybe those F&T traps aren't necessary. A templestik crayon won't help with testing those F&T either as the condensate can be as hot as steam.

More info needed about the overall system.

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scott75

It is one pipe

There is only one pipe connected to each radiator. Every radiator has an air valve. The end of the horizontal mains enters a FT trap, and then there is a return line from that back to the boiler. There is no air valve on the horizontal mains, only at the end of the returns right before the boiler. There is also a vacuum breaker valve.