Unified Thread Standard Question

[sbush]

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

S. Bush

http://www.water-eg.com

 

[metalonis]

No.

 

[OTHGWayne]

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.

 

[ApC2Kp]

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.

 

[KernOily]

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.