Pressure/temperature ratings of fittings

[ncstate86a]

We are currently investigating the installing a 16" nps 0.500" wall pipe to carry 1200F air at 450 psig. Due to the manufacturing dimensional tolerances of SA312 Type 316, the maximum allowable working pressure calculated per B31.1 is below the design pressure of 450 psig. Instead we have decided to use SA358 Type 316 Class 1. SA358 maintains much tighter manufacturing tolerances as it is made from plate rolled and electric fusion welded (class 1 requires 100% radiograph). Due to the tighter tolerances, the maximum allowable pressure at 1200F is 471 psig.

My question is this: How can I ensure that the fittings I buy (elbows, tees, conc reducers)will meet the pressure/temp requirements? SA403 WP-S/WP-WX is what we normally use with SA312. How can I be sure it will meet the higher pressure allowables of SA358. According to B16.9, the manufacturer calculates the pressure ratings...is this something that the fitting manufacturer provides? Is there a certain specification for fittings that is more in line with SA358?

 

[vesselfab]

About the only thing that is really different is the 12.5% mill tolerance in the pipe and is also considered in the fittings.

I would think that this may become big problem to overcome.

I would ask your local athority about it.

 

[GenB]

fittings need not cut 12.5%
the Mfr can provide calcs
purchas the ASME ANSI Stds for the fittings you are using
you have it all now.