NFT250 Series Float & Thermostatic Steam Trap

March 2023 in Condensate Return, Energy Management, Heat Transfer, Multimedia/Resources


NFT250 Series Float & Thermostatic Steam Trap

NFT250 Series Float & Thermostatic Steam Trap. NFT250 Series are float and thermostatic steam traps. Float is free of levers, linkages or other mechanical connections. This float is weighted to maintain orientation and acts as the valve being free to modulate condensate through the seat ring. Air vent is balanced-pressure design with stainless steel welded encapsulated bellows capable of discharging air and
non-condensable gases continuously within 15°F / -9.4°C of saturated temperature.

Principle of Operation

On startup, the thermostatic air vent, caged stainless welded bellows, is open, allowing air to flow freely through the vent valve orifice. When condensate flows into the trap, the float rises, allowing condensate
to be discharged. Once air and non-condensables have been evacuated, hot condensate will cause the
thermostatic vent to close. Condensate will continue to be discharged as long as condensation occurs. During normal operation, an increase in the load causes the liquid level in the trap to rise. The float then rises and rolls off the seat ring, allowing more condensate to flow out. The float sinks as the condensate load decreases, moving nearer to the seat ring, decreasing the effective size of the orifice and allowing less condensate to discharge. This provides smooth, continuous operation that reacts instantly to load
variation while maintaining a water seal over the seat ring to prevent live steam loss.


Install the NFT250 Series Float & Thermostatic Steam Trap upright and in a horizontal line with the arrow on the body pointing in the direction of flow. Allowable inclination is 5° or less horizontally and 5° or less at right angles to the plane of the pipe line.


Due to normal wear that may occur, inspect the parts periodically and replace if necessary. The frequency of inspection depends on the severity of service conditions.

For more steam system tips, please go to For more information on the types of steam boiler room equipment, please visit

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