Steam F&T Piping

BAB

We have a two pipe steam system. Most of the original steam main drip legs were piped correctly, except the steam traps at the bottom were always mounted directly to the drip leg (see attached photo). Reading here & there (Hoffman data sheets & books bought on this website) we learned that the piping before the trap should be at least five feet of horizontal before feeding the trap. We have changed some drip traps to have the horizontal piping & have noticed the better temperature difference & the cooler trap operation. Because of space constraints we usually use a loop, serpentine or zig/zag design. We have done 3-4 and have another 20 plus to do. We are doing them selectively for now.

My question has to do with F&T traps at the end of the steam mains. We have about 7-8 of them to update. We assume the same 5-6 feet of horizontal piping is also recommended. (also will put a Y strainer before each F&T trap)

Do we include the horizontal piping for F&T traps ?
Bromley

Jim Bennett

F&T......

traps don't need the 5' of horizontal piping. When using a radiator trap this way, the long pipe acts as a cooling leg so condensate gets to the approx 140 degrees where the thermostatic element will open.

F&Ts open with a thermostatic element and also a float so they pass condensate no matter what temperature.

BAB

radiator vs drip leg

We were referring to the drip legs from the main steam supply lines, not radiators. We have one steam main that goes the length of the building. It starts as 3" pipe size and eventually has three branches of 2" and/or 1-1/2" pipe size. The entire pipe run is about 350 feet. We have 3 midway condensate vertical drip legs from the steam main before the main end drip legs. Bromley

Steamhead (in transit)

Jim nailed it

in some cases, radiator-type traps are used on these main line drips, as shown in your pic. These need cooling legs. But if F&T traps are used on these drips, they don't need cooling legs.

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BAB

all clear now

I initially did not understand Jim's answer. Your clarification/confirmation/verification makes it all clear now. Thanks to both for the comments. Bromley