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A constant hanger supports a pipe over a larger range of movement with an almost constant supporting force.
A spring carries less the further it relaxes. A constant hanger compensates for this with a mechanism: a lever or cam arrangement changes the leverage so that the force at the hanger rod stays almost the same over the entire travel although the spring force changes. Other designs achieve the same with additional compensating springs.
The pipe can thus rise and fall without its weight being redistributed among the supports.
With a variable spring hanger the change in load grows with travel. For large vertical movements – for instance on long vertical runs of hot lines – or very tight limits on load variation, no spring can be found that satisfies both. The constant hanger is then the right component.
Typical locations are main steam and hot reheat lines in power plants and lines at turbines and other machinery with very low allowable nozzle loads.
The advantage of the constant hanger is also its weakness. A variable spring adapts to some extent: if the line is heavier than assumed, it deflects and carries more. A constant hanger carries exactly the set load, no more and no less. Every difference between assumed and actual weight ends up entirely on the neighbouring supports and connections.
The weights of pipe, insulation, valves and contents therefore have to be determined accurately. Constant hangers can be adjusted on site within a range stated by the manufacturer – as a correction for small deviations, not as a substitute for a weight balance.
A constant hanger is specified by load and total travel. The travel is chosen with a reserve beyond the calculated movement so that the hanger does not reach its stop if the line moves slightly differently from the calculation. Like a variable spring hanger it is delivered locked and stays locked during erection and the pressure test.
A constant hanger has a travel scale. In the cold and in the hot condition the indicator should be at the intended marks. If it is at the stop, the hanger no longer carries a constant load; the line is then supported rigidly or not at all.
What Entracon offers here is on the matching page.
See what we offer| Support | Supporting force over travel | Suitable for |
|---|---|---|
| Rigid hanger | Permits no vertical movement | Locations without significant vertical movement |
| Variable spring hanger | Changes by spring rate times travel | Small to medium travel, limited load variation |
| Constant hanger | Stays almost the same | Large travel, very sensitive connections |
Almost. Friction in the mechanism and manufacturing tolerances cause a small deviation over the travel, which the manufacturer states for the design. It is much smaller than the load change of a variable spring hanger.
Technically yes, but it rarely makes sense. Constant hangers are larger, heavier and more expensive, and they do not forgive an inaccurate weight assumption. Where a variable spring keeps within the load variation limit, it is the more robust solution.
The hanger has used up its travel: the line moves further than assumed, or the load is not right. In either case the cause should be established before any adjustment is made.
One short conversation usually settles more than three quotations. Call or write — you will reach an engineer directly.
Start typing – for example “balancer”, “SAP” or “pipe stress”.
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