Re: [MW:14599] PWHT requirement as per API-650

if u working in tank when u open shell and weld nozzle above 12mm must me PWHT shell with nozzles assemply befor ercting as a assembly (u put in to furness)

On Tue, Jun 19, 2012 at 1:10 PM, Thomas Cholamattam <thocho37@gmail.com> wrote:

Hi all,

Could you please interpret the code sub clause correctly.

What does it actually meant by?

the PWHT requirement is applicable only if it is above 25mm thick for NPS 12 or above diameter openings?

5.7.4.2 When the shell material is Group I, II, III, or IIIA, all opening connections NPS 12 or larger in nominal diameter

in a shell plate or thickened insert plate more than 25 mm (1 in.) thick shall be prefabricated into the shell plate or

thickened insert plate, and the prefabricated assembly shall be thermally stress-relieved within a temperature range of

600°C – 650°C (1100°F – 1200°F) for 1 hour per 25 mm (1 in.) of thickness prior to installation. The stress-relieving requirements need not include the flange-to-neck welds or other nozzle-neck and manhole-neck attachments, provided

the following conditions are fulfilled:

a. The welds are outside the reinforcement (see 5.7.2.4).

b. The throat dimension of a fillet weld in a slip-on flange does not exceed 16 mm (5/8 in.), or the butt joint of a weldingneck

flange does not exceed 19 mm (3/4 in.). If the material is preheated to a minimum temperature of 90°C (200°F) during

welding, the weld limits of 16 mm (5/8 in.) and 19 mm (3/4 in.) may be increased to 32 mm and 40 mm (11/4 in. and 11/2 in.),

respectively. 

Cheers,

Thomas Cholamattam

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