11.0 Impulse Tube/Sensing Line Support

Following principals should be followed while designing the instrument sensing line supports.

Hanger, support and clamps design should include provision for seismic, pipe whip and thermal expansion of process taps and instrument sensing lines to which the hangers, supports or clamps may be subjected during normal operation, seismic or other credible events.

Material for hanger, clamps, pads and spacers in contact with sensing lines should be compatible to avoid corrosion.

From the consideration of seismic qualification the following supporting criterion should be followed:

a) Supports should be placed at a distance of about 150 mm from each end of tube fittings as well as bends in the tubing layout.

b) Instrument isolating valves or other instrumentation valves coming in the sensing lines should be supported with suitable clamps.

c) In the intermediate tubing runs supports should be located in such a way that the maximum unsupported span is not more than 1m.

From the consideration of thermal loading, tube fittings and bends coming in the sensing lines should not be supported. This criterion will be applicable for sensing lines/tubing where temperature cycling is expected.

Tube Clamping

Once you’ve taken the time to make good bends and installed them, it’s not enough to just let them lay suspended in mid-air. When tubing is left unsupported, shock and vibration will cause the tubing to shake, and in turn, cause the fitting to loosen and leak or even allow tube to fall through fatigue.

Tube support and clamping is a necessary requirement in the fluid power industry. Tubing can be clamped individually, in sets, and can also be stacked. The most important part of any clamping system is having enough clamps to attain the final result. That being, a well supported, vibration and noise free system.

Also, most manufacturers specify SAE and JIC approved components on their equipment. The best way to meet these specs concerning clamps is to utilize a clamp that employs both an upper and lower unit made of metal and a rubber split bushing which surrounds the tube or pipe and fits on the inside of the clamping units.

Parker Hannifin offers a tube clamp support system by the name of “ParKlamp”. ParKlamp can clamp and support tube fro m 1/4” to 2” and pipe or hose fro m 1/4” to 1-1 /2”. It comes standard in steel and uses a rubber grommet around the tube for vibration dampening.

Alongside Table-11-1 is showing maximum permissible spacing between clamps. It is recommended to clamp as close to each bend of the tube as possible; and one must clamp each side. This eliminates thrust in all directions. The tube should be clamped at 1 m distance preferably. (See class-1 Tubing design)