Spring can or just bolt it? 1

[bigsteve80]

I am developing a vent to allow us to superheat a steam export line during startups (to be used 1 or 2 times a year). It will be a 3" SHC40 carbon steel pipe, with a silencer at the top (95 Lb). It will vent up to 50,000 Lb/hr of superheated steam, up to 750°F. I have a pipe rack structure available, with supports at 12, 17 and 22 feet up, and am thinking of continuing 3 feet above the structure, with the silencer on top of that. My concern is on thermal expansion; with such a large temperature differential, I show a thermal expansion of 1.5 inches. What is the best way of mounting the pipe? Do I need spring cans at the top and bottom, and u-bolt it at the 12 foot height? Or can I rigid-mount everything? Rigid mount at the top and let everything hang? Thanks.

 

[pennpiper]

How about a sketch of your proposed plan?

Sometimes its possible to do all the right things and still get bad results

 

[Ehzin]

For whatever reason the explanation regarding it's purpose is confusing me some. Regarding the pipe routing could you explain it a bit more. You've mentioned supports at 12, 17, and 22 foot elevations but what's the arrangement at grade. Does it come off directly off an exchanger and run vertically upwards? Would request a sketch of the piping if possible.

Thanks,
Ehzin

 

[BigInch]

No spring cans should be used. The silencer is not motion sensitive. I'm pretty sure that it can be allowed to move upward 1.5in. Direct all growth of vertical pipe stack to the up direction.

NO U-BOLTS!!! If there is any lateral velocity component of the exhaust it might cause turbulence which may eventually add lateral load to the top of the pipe. You should use a more substantial form of guide whenever there is potential for something more than a nominal forces, such as a full collar clamp made of plate steel as thick as the pipe's wall.

Hold up this pipe near the bottom of the stack using a vertical guide and stop that will prevent any lateral and downward movements. Design the stop to take the full weight of pipe and silencer plus exhaust thrust load. The pipe, connecting the stack from the exhaust take-off point to this vertical stop support, should have enough flexibility so that the vertical exhaust stack and silencer does not lift up off this first support when the stack heats up. The connecting pipe should be free to move downward at the vertical stop point without experiencing any overstress.

Place guide collars at 12, 17 and 22 ft elevations, only to limit lateral movements. They will not be designed to restrict vertical movement of the stack, nor take any vertical loads.

Allow for movement of flashing around the pipe where it goes throught the roof.

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