Constant-tension Clamps Outperform Adhesives

Feb. 6, 2003
Basics of Design Engineering - Fastening & Joining

Constant-tension clamps outperform adhesives

Constant-tension-band hose clamps (above) offer quicker assembly, better quality, and a cleaner appearance than glued pipe connections (below).

Adhesives are often touted as being better than mechanical fasteners. But they are not always the best solution when it comes to meeting consumer demand for quality products at low cost, according to officials at Sundance Spas, Chino, Calif. (, the world's largest manufacturer of acrylic hot tubs.

Part of the company's success lies in their ability to assemble products efficiently. Sundance recently improved manufacturing efficiency and quality even more by switching from glue to self-compensating, constant-tension-band (CTB) hose clamps from Rotor Clamp, Somerset, N.J. (

Previous to using CTB clamps, Sundance glued pipes to plastic fittings. The lengthy process involved applying primer, then glue, to the male and female ends of the fittings, mating pipe to the fittings, and finally waiting for the glue to dry. In addition, pipes had to be inserted inside the fittings, which made it difficult to determine pipe insertion depth and increased the chance of error. To further complicate the process, inspectors had a difficult time determining whether the proper amount of glue had been used, and if the pipe was seated against the fitting socket or had partially backed out.

With CTBs, workers simply slide the pipe onto fittings and tighten the clamps. Connections are clean and neat, and CTBs connect pipes on the outside of the fittings. This ensures proper seating and good connections, which cuts down on defects. The design is also more flexible, permitting a wider tolerance range on pipe and fittings, as well as post-assembly adjustment. If permanently glued fittings and pipes need to be adjusted, they must be taken out and replaced.

Switching to CTB clamps offers several other benefits. Instant-use plumbing eliminates hour-long waits required for solvent welds to dry before testing. Fewer steps shortens assembly time, making manufacturing more efficient and consistent. And workers are no longer exposed to volatile organic compounds - the plumbing process is now fume-free.

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