SUPPORT LOADS ON A 12" STEAM LINE 1

[JTHEVENET]

Iam working on the flexibility of a steam line going from an existing manifold(Ti-in)to a steam turbine. Here are the calculation conditions: 490°C(about 900°F); 3Mpa; Pipe: 12" thk:0,885".
This line runs along a rack, I designed some loops (2 loops) to improved the flexibility. I guided and blocked the line on each side of the loops to let the loops work correctly. When I look at the result the stress is Ok (well bellow the allowable stress). But the restraints on each blocked support(block the axis pipe displacement)on each side of the loops are about 60000N (Newtons). Can a normal designed support hold this load ? Is there a rule that exist that gives the maximum restraint a support(shoe type) can hold?.
When I looked at some others report calculations that we have done on others projects, I see that for the same type of conditions and the same type of pipe, the axial restraints are about half what I got (about 30000N).

Thank you very mush in advance, any advice will very welcome!. I really appeciate this site!

 

[DSB123]

JTHEVENET,
60000N is a very small load in reality (6 Tonnes) and should easily be accommodated. Any reasonable Structural Engineer/Civil Engineer should be able to design a support to accommodate the relatively small load. The only problem could be where the pipe is routed. If its local to the ground then 60000N is nothing whereas if its 10metres up in the air then it can still be accommodated but the structure could be significant. The limit on the level of load is dependant upon the locality of pipe (i.e. up in the air or at ground level) and the actual wall thickness of the pipe since local stresses in the pipe wall have to be accommodated without exceeding Code allowable stresses.

 

[StressGuy]

With your conditions, your anchor loads do seem unreasonable. You will find, particularly as the line size increases, you will more often run into the structural steel as the limiting factor on your loads before you overstress the pipe. I've often has to make loops larger than required for stress in order to reduce the anchor loads.

Your wall thickness is pretty high, so you probably don't have a problem, but one other thing to be aware of is the local stresses at the shoe/pipe interface. With a typical 4" shoe height, you don't have a lot of bending moment for an axial load, but particularly with a single web shoe, you can easily overstress when you have a lateral (guide) load.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.

 

[JTHEVENET]

Thanks a lot, actually I took the option to design 3 loops instead of 2 along the rack.That way I reduced the restraint at 25000N (axial force)wich seems more reasonnable for me in term of stability of the line.