90 Year Old B&J Trap Design Increases Performance of Today’s High Tech Systems

Steam Trap
Barnes & Jones was founded before the turn of the century by two engineers, Walter Barnes, a graduate of The Massachusetts Institute of Technology, and Bill Jones a graduate of The Worcester Polytechnic Institute. Around 1897, the two joined forces to design and layout two pipe central steam heating systems for new construction in and around Boston, New York City and Chicago.


By applying their engineering expertise, the partners built a reputation for quiet, trouble free and efficient systems. Most steam traps of the day were inefficient fixed orifice types or troublesome carbon post or bi-metal designs. The inherent limitations of this type of trap defeated the efficiency of the systems designed by Barnes & Jones, so the two contractors became inventors and introduced their own improved thermostatic trap in 1902.

The new traps featured a bellows, containing a small amount of distilled water, with a ball and seat to provide rapid venting and positive closure at the exact flash point of steam. Barnes & Jones traps were an immediate success. Not only did systems operate more efficiently, but the traps seemed to be almost immune from failure. Soon, Barnes & Jones began to supply traps to other contractors and plumbing suppliers in Boston, Hartford and Providence.

Trap failure, however, is inevitable. After more than twenty years in service, the original traps began to lose their efficiency and pass steam or fail to vent. Worse, the delicate bellows required precise alignment within the trap body for a repair to be effective. Walter Barnes and Bill Jones recognized that the only way to properly maintain their traps was to pre-assemble and calibrate the repair kits at the factory. This one piece, calibrated repair kit was given the name “Cage Unit”.


By 1930 these Barnes & Jones thermostatic Cage Unit inserts had become a recognized standard in the steam heating repair kit market. Working as a complete trap within a trap, the new inserts made trap repair as simple as changing a light bulb. Best of all, the new inserts made every trap perform like new.

Within a year of the introduction of the Cage Unit insert, Barnes & Jones expanded their Cage Unit repair kit line to repair other manufacturers’ traps.

Today, Barnes & Jones Inc. manufactures 100% Calibrated Cage Unit inserts for every heating steam trap body ever made. Barnes and Jones products are available throughout North America, Central and South America and most of Europe by over 10,000 representatives. The operating principle, introduced in 1902, remains unchanged as Cage Units emerge, today, as the preferred automatic valving solution for high-tech environmental control systems.

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