weld joint strength reduction factor for A358 pipe & A403 fittings 1

[insider79]

Hello members,

Can you kindly help me out with below query?

1. I have to calculate the WT for A358-321 CL.1 pipe at design conditions of 800degC at 49.7psig. Am I correct in understanding that value of W must be linearly interpolated from values in the row "Austenitic stainless grade 3xx and N088xx nickel alloys [Notes (7) and (8)]"in table 302.3.5, which mentions 0.55 at 788°C and 0.5@ at 816°C?

2. If I use A312-TP321 EFW, I can substantially reduce the thickness since W=1 for all temp ranges. However, If I chose A312-TP321 EFW pipes, then should I specify that the welded wrought fittings A403-WP321 are mandatorily fabricated or made from welded mother pipes that have been fabricated without using filler metal? ASTM A403 gives the option of both. I am worried about the WT wrought fittings being affected due W factor stated in point 1.

Thanks
Regards

 

[jojoyohan]

1. You should interpolate.
2. You also need to ensure that your piping has not been weld repaired, which is allowed by A312 to be done with filler metal. A312 requires that it be noted on the test certs so you should be able to check that it is acceptable.
What is the cost difference between welded and seamless fittings at the size you need? Unless you are ordering a mill run already, I don't see how you get the information you need to use W=1 on welded wrought fittings.

 

[MJCronin]

At 800 degrees C (1472F) you are at the bleeding edge for that material. What happens when the operators "accidently" let the system run a little hot ...

The allowable stress curves end at 1500F ... as I recall...

MJCronin
Sr. Process Engineer

 

[GD2]

Insider79,

There are couple of warning notes under A358 TP321 in Stress Table A for usage above 583 C. Make sure that you have considered the appropriate basic allowable stress value while calculating the WT.
Linear interpolation is allowed by note (e) in Table 302.3.5

GDD
Canada