Constant effort spring support and Variable effort support. 1

[07071975]

Hi Dear all,


I am little bit confused with Constant Effort spring support and Variable Effort Spring support.

What is basic difference between these? What is the selection criteria.

 

[BigInch]

Constant effort springs put a constant force on the pipe no matter what the actual movement at the point is, whereas vairable springs put a force on the pipe that is more proportional to the spring deflection.

A constant effort spring, for example, is often used to support only the weight of the pipe and constants with little actual dependence on how much the pipe moves at that point.

A variable effort spring is convenient to use when you want to resist the pipe's thermal expansion, because the more the pipe tends to move, the increased tension or compression of the spring will deliver a larger countering force to the pipe.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[ApC2Kp]

07071975,
The selection of spring supports would have requirement of the load to be carried, and the vertical movement of the load. Hence, spring support manufacturers have a variety of standard production models, and the support for a 0.500 inch displacement variable spring is much smaller unit than the support for 5.0 inch displacement constant effort unit. Also, the cost is much more for the complexity of cams and gears in the constant effort spring support capable of 5.0 inch displacement. You will have additional requirements of installation height as the spring support progressively adds travel capacity from the old Grinnell Figure 82, to the B-268, then Figure 98, and then the constant effort type supports.
The constant effort spring support will corrode and bind up after a moderate time in typical chemical plant environments. The cams and gears will have a chance to survive within the possibly cleaner atmosphere of a powerhouse, but cleaninng and maintaining lubrication of a constant support spring unit is recommended by their manufacturers and users like B&W boiler.

 

[JohnBreen]

Hello 07071975,

Perhaps you might benefit from reading the Anvil (Grinnell) manual regarding design of pipe supports. It is a free .pdf file that you can find here:

http://www.anvilintl.com/db/datasheets/Pipe_Hanger_Design-05.pdf

Regards, John.