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Differing Pipe Schedules

Differing Pipe Schedules

Differing Pipe Schedules

(OP)
Hello All,

A project I am working on now is a valve replacement in a 24" bypass line at one of our dams.  The bypass line and valve has been in service for about 50 years.  

The original specs we have state that the bypass pipe is to be carbon steel pipe (equiv. to ASTM A 53, Elec. Resist. Welded, Grade A) to be manufactured from 1/4" thick steel sheet.  Looking at the charts in the ASTM, this would indicate SCH 10 for a 24" pipe.

A majority of the pipeline is located within a concrete wall.  Only a small portion of the line is exposed where the valve is located.  The piping protruding from the wall is coupled to the exposed piping with Dresser No. 38 couplings at each end.

If reasons dictate that a different schedule pipe is required (for example SCH 20, aka Std Weight for 24" A 53 pipe), will there be a problem due to the 1/8" difference is wall thickness (erosion, flow problems, etc.)?

Thank you,
 

RE: Differing Pipe Schedules

Are you still going to use a Dresser Coupling to connect the two pipe sections together?

If you use the coupling all I would taper (3::1) the .375" wall down to approximately the .250" existing. The pipe faces should be as square as practical.  

RE: Differing Pipe Schedules

Mismatch of up to 3/16" will usually suffice for welding without taper bore.

http://virtualpipeline.spaces.msn.com

"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain

RE: Differing Pipe Schedules

(OP)
Thanks for the input guys!

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