ARE CONSTANT TENSION HOSE CLAMPS EFFECTIVE?

Our tests show that JCS’s Hi-Torque hose clamps outperform industry-standard constant tension hose clamps. We are sometimes asked by clients how our hose clamps compare with constant tension hose clamps – a different design of hose clamp to the hi-grip and hi-torque worm drive clamps we manufacture at JCS. DESIGN FLAW The idea behind constant tension clamps is that during tightening the Belleville washers compress, acting like a spring. When the rubber relaxes the spring action pulls the band through the housing, so making the clamp smaller to compensate for shrinkage in the rubber hose. However, we believe the basic engineering principles underpinning this design are flawed. The idea that a spring can modulate the amount of pressure a clamp exerts over time and under a range of extreme environmental conditions just doesn’t hold water – in some cases literally!!! In effect you are putting a spring in a pressure system and when the pressure of the fluid exceeds the spring tension you have a leak.(See below) NO SUBSTITUTE In our experience, there is no substitute for clamps that are made to the highest quality and strength combined with innovations such as JCS’s ‘straight line’ housing, which ensures that every thread of the screw is fully engaged with the band to provide more torque. We are constantly running tests at our workshop and we recently carried out a number of laboratory assessments on a sample of industry-leading constant tension hose clamps as well as our own clamps to compare how the different designs perform. TESTS PROVE CONCLUSIVE We tested six constant tension hose clamps of different sizes made by a respected clamp manufacturer from the USA. They claim the Belleville washers enable the clamps to cope with ‘fluctuating and extreme temperature applications and thermal compensation’. We ran a number of tests recording at intervals the grip of each clamp on a calibrated test rig to measure the clamping force. These included a 24-hour rubber cold flow test, and a test where the assembly was heated to 125°c for five hours. Both types of clamp were then tested on a hydraulic pressure tester after the cold flow and heat cycle. In addition, our test professional performed a salt spray corrosion-resistance test, where the clamps were bombarded with salt water. While the JCS clamps remained unaffected, we found rust forming on the constant tension screw in under 24 hours. The tests also revealed what we’d known all along – that the constant tension ability of the clamps is quite limited and the capacity of the springs to compress can be a liability. On most tests, under identical conditions, our conventional HTM clamp substantially out-performed the Belleville design.

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