NPT pressure ratings 4

[CajunCAD]

Is there are reference source on the net that I use to find the pressure ratings for NPT connections?

Specifically, I need to know the ratings on 1/4" & 1/2" NPT connections.

Thanks

 

[EdDanzer]

The pressure is going to be controlled by the ID of the fitting, hose or pipe in most cases. At pressures over 1000 psi sealing the thread becomes a problem. The internal thread is usually tapped so you have a line at each flute that doesn't seal well.

 

[AJone]

Swagelok is a good safe reference for this. Check out the following link:

http://www.swagelok.com/downloads/webcatalogs/MS-01-147.pdf

Obviously the max rating will depend on the application, forces on the connection, connection material, safety factors, etc.

NPT threads are capable of sealing reasonably well at higher pressures but other connections types are much more reliable.

 

[abbver98]

ASME B31.1 114.2.1 :
NS < 3&quot; : max 27.5 bar
NS < 2&quot; : max 41.5 bar
NS < 1&quot; : max 83 bar
3/4 and smaller: max 103.5 bar

 

[EdDanzer]

The reason I stated the pressure limit is in relation to the ID is I have pressure transducers with ¼” and ½” pipe thread that have 20,000 psi ratings. I have tested ¼” pipe to 20,000 psi several times.
Barlow’s formula will determine pipe yield and burst, the thread will be limited by the yield of the male and female materials, and the tensile stress area of the threads. Again the bore will effect the tensile stress area of the internal thread.