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Re: [MW:7277] Re: pwht vs hardness

By Materials & Welding
Hi,
 
AS per Table 331.1.1 (Requirements for Heat Treatment) of ASME B31.3, carbon steel pipes above 19mm require PWHT.
 
Moreover  SA 672 is

Specification for steel pipe: electric-fusion welded with filler metal added, fabricated from pressure vessel quality plate of any of several analyses and strength levels and suitable for high-pressure service at moderate temperatures.

 

Class -designates the type of heat treatment performed during manufacture of the pipe, whether the weld is radiographically examined, and whether the pipe has been pressure tested.

 

Grade designates the type of plate used.

 

Cl22 means , its a stress relieved pipe ( refer 5.3.1 and table 2 of spec).

 

So the pipe itself is stress relieved and you have said it is flare line. Please check the properties of process fluid ( especially H2S,NH3) which may flow inside. Mostly flare lines are prone for SSC and it may call for NACE MR103 for material & NACE RP 472 for welding also.

 

Moreover hardness test is not an substitute for PWHT. AS per 331.1.7 of ASME B31.3, hardness test is intend to verify the satisfactory heat treatment.

 

Hardness test will not indicate any residual stress present.

 

 

You have not mentioned the grade of steel . If it is carbon steel, what is your cut off limit? Because hardness limit is not given in ASME 31.3 for carbon steel.

 



On Wed, Sep 29, 2010 at 10:10 PM, Raghuram Bathula <raghurambathula@gmail.com> wrote:
PWHT is mandatory by code for that thickness.

On Sep 29, 9:16 pm, "sunilrathor...@yahoo.com"
<sunilrathor...@yahoo.com> wrote:
> Dear member,
>
> We have an pipe made from sa 672 cl 22 mat having dia 72" and thk 22 mm used for flair line in refinery. The construction people are taking devation not to do pwht on basis that they will check the hardness value if it comes under limets they will not do pwht.
>
> i want to know that is hardness testing is substitute for avoiding sr or pwht
> .
> Its design base is asme 31.3
> n Patel
 Worley Parsons, London

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With Regards,
Sudharsan

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