Radiator Steam Traps

Thermostatic Steam Traps For Low and Moderate Pressure Service


Thermostatic Steam Trap Specification Sheet


  • Heavy duty cast bronze or forged brass body
  • Forged brass cover, union nut and tailpiece
  • Corrosion resistant seat and plug with option of stainless steel
  • All working parts factory calibrated within “Cage Unit” ensuring absolute uniformity of performance
  • 100% factory tested under live steam & condensate
  • Available in angle, straightway or vertical piping patterns
  • 1/2”, 3/4”, and 1” pipe sizes
  • Also available, 1/2″ inlet x 3/4″ outlet design


The purpose of a steam trap is to prevent steam from passing its point of use and to allow condensate to be expelled as soon as it forms. Barnes & Jones’ thermostatic steam traps perform this function better than any other traps available today. Ours are the only factory calibrated thermostatic steam traps; a claim that cannot be matched by Dunham Bush, Sarco, Hoffman, lllinois or any other manufacturer. Calibration ensures that each of our thermostatic traps snaps shut to steam and opens to condensate with a uniform sensitivity that has been proven under live steam in our factory test facility. You no longer have to worry about the tolerances of individual parts, such as the “screw in” seat, lock washers, element and cover of other traps. lt is our one piece, fully removable, thermostatic element, the Cage Unit, that is the heart of our trap. The body of the trap acts merely as a housing for the Cage Unit, which performs all the work. Additionally, testing of this element can be performed out of its original trap body, in a test body, due to its stand alone, calibrated construction, thereby eliminating the need to take the trap off line for testing or repair and greatly simplifying your preventive maintenance program.


Using a diaphragm or bellows, within which is a volatile liquid, sealed under vacuum, the trap opens and closes in a modulating manner dependent upon the temperature affecting it. The trap’s normal state is that of being wide open to expel air and condensate. When surrounded by steam at saturated temperature, the volatile fill has flashed, creating an internal pressure equal to the surrounding pressure. This equalization of pressures allows the bellows to expand to its natural length or “closed” position, preventing steam from passing. The presence of condensate sufficiently cools the bellows to condense the vapor within. Once again the external pressure is greater and the bellows reverts back to its contracted, or “open” position, allowing the condensate to drain from the trap, permitting more steam to enter the radiator and thus, the modulating action of the trap.