[MW:1541] Re: Significance of HOT PASS

I agree with the view of Herman, but partly.

It all again depends on the location of weld. If it is shop-weld, one need
not worry for cracking, particularly, the possibility of cracking is more
in higher thickness, where self weight of pipe and also the constraint will
be significant.

Even in case of erection joint, where there is a high constraint due to
other spools connected to it, one may go for LPT/MPT before re-starting the
out-pass welding. Also, the preheat at min. 75 deg.C will help remove the
moisture/greese and dirt/other impurities on the weld surfaces.

For the above risk only, many Clients do not allow discontinuation of
welding before welding at least 50% of the thickness. Please take care of
any such requirements.

Best regards,

Prasad

pieper-qsi@kpnmai
l.nl
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09/02/09 09:07 PM
Subject
[MW:1532] Re: Significance of HOT
Please respond to PASS
materials-welding
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Dear Rafique,

I'm an international welding technologist and perform a lot of weld
inspections but I never accept stop welding when only root layer is
applied. In my opinion also international regulations won't accept
such. One of the most important reasons is the possibility that cold
cracks arise in the root layer. If you still need to stop after the
root layer in my opinion you have to perform NDT in front of welding
to ensure that there are no cracks in the root pass, after that I
would propose to preheat up to 75 - 125 °C in order to remove any
possible moisture arised because of cooling down after root layer.

Best Regards

Herman Pieper

On 8 feb, 18:16, rafique naik <rafiquen...@hotmail.com> wrote:
> Please let me know for A 106 B 16'' dia  12.7 mm thik pipe to pipe butt
joint, if after root pass joint is left as it is for overnight and next
morning welder wants to continue with hot pass, can he do welding  without
any pre heating..
>
> Regards
>
> Rafique
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