3mm weld overlay in API6A requirement

[yudhichen]

Dear folks,

Anybody can share me whats the reason behind '3mm' weld overlay, especially in API6A?
i look around the fact why '3mm' and i heard its related to dilution problem.
but i'm not so sure since i'm not familiar with welding.
does it mention somewhere (i.e. ASME IX), so that API took it as a common practice?

Thanx

 

[denlow60]

API 6A
6.5.1.2.1 General
This subclause applies to use of corrosion-resistant weld overlay for bodies, bonnets, hub end connectors, and end
and outlet connectors for purposes other than ring grooves. These requirements do not apply to hard facing or to
the weld overlay of valve-bore sealing mechanisms, choke trim, or valve stems.

6.5.1.2.2 Welding procedure/performance qualification
Qualification shall be in accordance with ASME, Section IX, Articles II and III for weld overlay.

look in ASME IX .

 

[yudhichen]

i look around that ASME sec IX art II & III, but i didnt find any word for saying 3mm...
do you have any clue where this magic number come from?

why not 4mm? 5mm?

anyway, thanx to reply.

 

[denlow60]

Chemical analysis shall be performed on the weld metal in accordance with the requirements of ASME,
BPVC:2004, Section IX, at a location 3 mm (0,125 in) or less from the original base-metal surface. The
chemical composition of the deposited weld metal at that location shall be as specified by the manufacturer.

QW 350 , 360 , 453 .

 

[Guest102023]

Do not expect to achieve corrosion resistance at 3mm by conventional welding processes.
Three layers are usually needed, and realistically that will produce 7 to 10mm thick overlay before finishing.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"