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Float and Thermostatic Steam Traps (F&T traps)

Yarway™ F&T steam traps are well suited for process applications due to their wide rangeability.

What are Float and Thermostatic Steam Traps?

Float and Thermostatic steam traps (F&T traps) are included in the mechanical trap category, operating off the density difference between steam and condensate. These F&T traps are actuated by a ball floating on the condensate. As the condensate level rises, the float opens the valve, removing condensate. Although it is one of the oldest types of steam traps on the market, the float trap is still in widespread use.

F&T traps are energy efficient, continually discharging condensate close to the saturation curve, and can operate with high backpressure. Float traps respond very well to changing condensate loads and pressure swings and the built-in thermostatic element removes air efficiently, making F&T steam traps the number one choice for process applications.

When selecting a trap for a process application, one common limitation to consider is floats can be damaged by freezing during shutdowns. For drip applications, alternative technologies are preferred whose predominant failure mode is in the open position, preventing water hammer damage in distribution equipment. Similarly for tracing applications, alternative technologies are preferred whose predominant failure mode is in the open position, ensuring the heated equipment stays warm.

Steam Trap Selection Guide

Stream Trap Selection Guide

Reliable Solutions for Steam Generation & Distribution Applications

Reliable Solutions for Steam Generation and Distribution Applications

FAQs

When the trap is empty, the weight of the ball float closes the trap. As condensate enters the trap, the float rises and opens the valve, allowing condensate to be discharged. The float is designed to provide sufficient force to overcome the differential pressure across the valve. The internal float and valve configuration is such that the condensate level is always above the valve, thus creating a continuous water seal at its seat. While most designs employ a pivoting lever, leverless designs are also available.

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Float and thermostatic traps can fail in either a closed or an open position. They fail to close if the float is ruptured by a water hammer and can no longer rise to open the valve. They fail to open when the main valve and seat or thermostatic air vent valve and seat are worn or eroded so that they leak steam.

If the F&T trap is hot: Because the trap is designed to drain condensate continuously, verification that it is not leaking steam is difficult unless the leakage is very large.

  1. Examine the trap discharge pattern for evidence of steam leakage.
  2. if possible, drain condensate through the strainer blowdown vent in front of the trap to determine if both trap and air vent valves can close tightly in the presence of dry steam. Tight shut-off establishes that the trap is functional.

 If the F&T trap is cold:

  1. Verify that the system is pressurized.
  2. Open the strainer blowdown valve to purge it of debris.
  3. Verify the system pressure does not exceed the rated pressure of the steam trap. This can prevent the float from opening.
  4. Close block valves and disassemble the steam trap to inspect for obstructions and examine internal parts for damage especially the thermostatic air vent.