Re: [MW:0] Re: STRESS RELIEVING REQUIREMENT

it does use SI Metric units first and US customary units in the parenthesis in general. however in case of PWHT it is indicated in both inches as well as in mm. PWHT limit is 20mm (if i am not wrong before 2004 edition it used to be 19mm) with 3/4" as well indicate in th next column. Hence no confusion over conversion.

On Tue, Jul 6, 2010 at 7:25 PM, Darc <morind@bantrelconstructors.com> wrote:

A couple of issues are raised here:

1.    ASME B31.3 is not a Metric standard...it is an Imperial Standard
with 'soft' Metric equivalents ...0.75" does not equal 20mm, it equals
19.05 mm, so care should be taken in the interpretation of PWHT
requirements, interpretation is based on the Imperial scale even
though the Metric scale is more precise.

2.    Unless I am overlooking something, Category D piping must meet
the design criteria set forth in the code.  I can find no exemption in
the design standard for this, regardless of the customer
specifications.  Although, it certainly would be more cost effective
to ignore code requirement for PWHT on P1 material greater than 0.75"
thickness...

Warm regards,

Darcy

On Jul 4, 6:24 am, des...@toyoindia.com wrote:
> Hello,
>
> As per ASME B31.3; for CS material PWHT requirement is above 20mm.
> Is this applicable to category D fluid service class also?
>
> Or code has given liberty to skip PWHT for category D fluid service even
> though thickness is greater than 20mm.
>
> Pls. advise.
>
> Thanks in advance,
>
> Thanks & Regards,
> Dhwani Desai
> Planning & Piping Dept.
> Ext.-7681

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