Float & Thermostatic Steam Trap Tutorial

Description of the operation of an Armstrong Float & Thermostatic steam trap.
When steam pressure may vary from maximum steam supply pressure to vacuum, Armstrong F&Ts are your most energy-efficient choice. Our line of F&Ts brings Armstrong performance, dependability and long life to trapping services requiring continuous drainage with high air venting capacity. Thanks to separate orifices for condensate and air, they provide continuous condensate drainage and air venting-even under conditions of zero pressure.
All the benefits detailed here have been designed into Armstrong F&Ts through long experience in the manufacture of pressure float-type traps. They assure you of optimum operating efficiency for long periods with minimum trouble.
How they work
Float and thermostatic traps are mechanical units that operate on both density and temperature principles. The float valve operates on the density principle. A level connects the ball float to the valve and seat. Once condensate reaches a certain level in the trap, the float rises, opening the orifice and draining condensate. A water seal formed by the condensate prevents live steam loss
Since the discharge valve is under water, it is not capable of venting air and non-condensables. When the accumulation of air and con-condensable gases causes a significant temperature drop, a thermostatic air vent in the top of the trap discharges them. The thermostatic vent opens at a temperature a few degrees below saturation, so it's able to handle a large volume of air-through an entirely separate orifice-but at a slightly reduced temperature.
Built as tough as the jobs they do
Armstrong float and thermostatic traps are unique in their super heavy duty construction. Armstrong uses high quality ASTM A48 Class 30 cast iron or ASTM A216 WCB cast steel-normally found in pressure vessels rated to 250 psi (17 bar) or 465 psi (32 bar). Internal mechanisms are made from stainless steel and are heavily reinforced. No brass cotter pins here. Valves and seats are stainless steel, hardened, ground and lapped to withstand the erosive forces of flashing condensate.
Why go to all this trouble for traps normally recommended for low-pressure, modulating service? The operative word here is modulating. Modulating pressures mean widely varying loads, thermal cycling and high air and non-condensable gas loads.
In other words: tough service. Inferior, lightweight construction in this kind of service is a mistake waiting to happen. Trap failures on modulating pressure may lead to water hammer, corrosion and even damage to heat exchangers.
Armstrong's published capacities are based on actual measurements of traps handling hot, flashing condensate. Competitive F&Ts may utilize theoretical calculated capacities. Armstrong uses its own steam lab to give you actual capacity-especially important on high-capacity traps such as those in our ultra-capacity line. Not only does Armstrong offer super heavy duty construction for long life and reliability, but we also supply the data to back up performance. Here's a simple, easy-to-remember summary: The more your pressure varies, the more you need Armstrong F&Ts.

[@Julia-jz5wt]

Wow thank you so much for sharing your knowledge with the world in an understandable way

[@nascar211288]

I also installed new wye strainer . Also the condensate tank has a chemical feeder , would this cause a problem in a f&t , air locks ?

[@Julia-jz5wt]

Wye strainers should go before F&T traps

[@nascar211288]

I install a new f&t steam trap , they don't have that tapping on top . Should I put one in,? I'm having trouble , condensate getting trapped , gallons of water comes out of clean plug on bottom of trap

[@ferozsanders989]

Maybe the selection is wrong or maybe possible sizing issues.

[@Ratman_Bejo]

operation of an Armstrong Float & Thermostatic steam trap.

[@Jughead55]

No. The thermostatic air vent is for venting air in the system. More likely the valve is not seating correctly anymore. Even with a through cleaning, these traps can go bad. You can change out the internals, but F & T's are usually not repaired in that they are cheaper to to just replace. You can contact your local Armstrong rep and they would be able to help you.

[@steventasker235]

I used to work in a hospital. All along the main steam line there would be a chitter chatter tapping noise, it sounded like morse code but not beeps. A guy I worked with said it was the traps on the drip legs. It seems like the only plausible explanation, the valve opening and shutting. However, if there are hundreds of taps/chatters a minute, the valve flickering open and shut like that, does that not suggest something’s wrong with the valve? Or is it normal for a trap to chatter like this? Any help would be greatly appreciated, I tried google but can only find pages discussing using electronic listening devices to hear through the static whether or not a traps functioning correctly

[@steventasker235]

Something wrong with the trap*

[@PyroDR]

I have these traps in the boiler room, after the lines that run through the rooms in the building. While I have taken all of these traps apart, and cleaned them, I am still getting a lot of steam coming from my condensate tank. My question is... Can failure of the thermostatic part of the trap cause steam to pass through the lines, even if the float is working properly?

[@Julia-jz5wt]

yeah you probably need to add an air vent

[@alexanderbelluccia599]

I am having the same issue, was wondering if you ever figured it out, I’m in the same boat and have steam dumping into my buildings condensate tank, but the float seems to function. I’m wondering if the thermostatic valve has failed and is stuck open

[@thesage823]

If I remember correctly, I turned off valves to find which line the steam was coming from, then replaced the tap on the line, and that solved it. That's been a long time ago, so I'm not that clear on it.

[@jgottardy]

mislabeled - does not discuss float