ASME BPVC Sec. I Table PW-39

[cnkn]

In ASME Sec. I Tabe PW-39-1 and PW-39-2 postweld heat treatment requirements are specified based upon the material thickness.The last colum of the table covers material thickness over 5 inch (125mm) but the explanation for the holding time is like this : " 2 hr plus 15 min for each additional ,inch (25mm) over 2 inch (50mm)"

My qustion is : The last column covers material thickness over 125 mm but the holding time refers to "over 50 mm "

Isn't this a contradiction?

If not , what is the explanation?

Thank you...

 

[metengr]

There is no contradiction. You have a range of nominal thickness for PWHT from 2" (50mm) to 5" (125mm). The holding time beyond 2" (50mm) nominal thickness is for each additional inch (25mm) of thickness is 2 hrs and 15 minutes. This same note is repeated to even thicker material above 5" (125mm).

 

[cnkn]

Let's go through an example.our material thickness is 75 mm.Which column i should take?i know the requirements for the last two column is the same.but the last column also covers the previous one? The explanation for the last column in the Table PW-39-1 should be "2 hr plus 15 min for each adfitional inch (25mm) over 5 inch (125mm) just as in the Table PW-39-3.

Did you understand my problem?

 

[metengr]

For a nominal thickness of 75mm, you would use the column in Table PW-39-1 between 50 mm and 125 mm. The hold time would be 1 hr per 25mm thickness, so for 75mm, it would be 2 hours (1 hr per 25mm) + 2 and 15 min (for an additional 25mm) = 4 hrs and 15 minutes hold time.