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Unified Thread Standard Question

Unified Thread Standard Question

Unified Thread Standard Question

(OP)
Will a female connection having a 4" 8UN thread (per ASME B1.1-1989) screw on to a 4" NPT pipe nipple?

S. Bush
www.water-eg.com

RE: Unified Thread Standard Question

No.

RE: Unified Thread Standard Question

No.  A 4" UN thread is designed for a thread that is 4" OD.  A 4" NPT is much larger than 4", closer to 4.25"-4.44" OD.

RE: Unified Thread Standard Question

sbush,
You will need to find Nps-3.5 pipe (4.0 inch od.) to thread and fit into the 4-UN thread.  It will not be leak tight, so a flange + gasket, or a counterbore + O-ring seal would be needed for pressure tight joint.

RE: Unified Thread Standard Question

Easiest thing is to get a machine shop to make an adapter to transition from 4" 8UN to 4" NPT instead of messing with flanges and o-rings.  Easy greasy.

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