internal pipe thread depth

bob16 · Jul 18, 2002

Given: Flanged discharge piping in high service potable water plant. Discharge piping is 30" and at 130 psi. Surge valve at end of run is 8". Desire is to install surge valve using 8" piping etc... We can get a 30" blind flange tapped for 8" pipe.

Question: Can we get a legal(spec) pressure joint by screwing a threaded 8" spool piece into a 2-1/8" tapped opeing? If not, any other ideas other than flanged reducers?

TBP · Jul 18, 2002

My old, old "Mechanical Engineers Handbook" by Marks shows the "Total distance pipe screws into fitting" as 1.46" for 8" pipe.

Can you use Victaulic or Gruvlok for this?

KernOily · Jul 18, 2002

Interesting question. I don't know as I've ever seen 8" screwed pipe.

If it's critical you can always get an FEM analysis done of the joint.

How about buttweld reducers? Remove the blind, then install a WN flange and a series of buttwelded reducers, then an 8" flange and then your valve. Thanks!
Pete

bob16 · Jul 19, 2002

Thanks TBP and 74Elsinore.
I like the fact that the thread depth is ok from TGP but I also wondered about 8" screwed pipe. We are using ductile iron (dip) in this project so butt welds may not be an option. Or is it? We have layed out two flanged dip reducers to get to the 8" size and it fits. that layout seems so wasteful.

Thanks for your help.

Bob

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internal pipe thread depth

bob16

Civil/Environmental

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