Significance of HOT PASS

[rafique naik]

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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[Sukamal Naskar]

Pre-heating is not as such required, but it is a good practice to use flame heating at the joint to remove the moisture or any foreign particles before starting the welding on the next day.

Regards
Sukamal Naskar
Welding Engineer 

--
Sukamal Naskar
Malaysia

[_konga]

it depends on how WPS stated about interpass temp. (this including
what code is used)
if there is no specific requirements, normaly will be kept higher than
5 degC.

regards,

- Eddy Konga -

On Feb 9, 12:16 am, 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

> _________________________________________________________________
> Wish to Marry Now? Join MSN Matrimony FREE!http://www.in.msn.com/matrimony

[nachiket vagal]

You can not stop before hot pass is completed.. If you have to then conduct NDT, preheat and continue. --- On Mon, 9/2/09, Sukamal Naskar <sukama...@gmail.com> wrote:

Unlimited freedom, unlimited storage. Get it now

[Paresh]

Dear Rafique,

 

First of all don’t make it practice to leave root welded joint. It should be left after hot pass completion.

If some case by mistake left , you have to do DPT to conform any defect occurred due to stress.

There are lots of way to create stress  on weld joint.  

 

It is better to cut root weld in higher thickness.

 

Thanking you,

 

Regards,

Paresh Patel
 

[Chaitanya Purohit]

Generally it depends on the WPS, being used. If WPS specify the pre-heating (at certain temperature) then it is mandatory to carry out preheat on next day morning prior to any strike.

 

As a Good engineering practice, and most of the client specification call for completing Hot pass prior to stop the welding. If you are stopping before ½ thickness deposition or hot pass, need to examine the root pass for defect by PT/MT to ensure that it is free from any cracking.

 

Regards.

 

C. K. Purohit

General Manager - QC

KNM Process Systems Sdn Bhd - Malaysia

 

HP No. : 6016-3376448

---

From: material...@googlegroups.com [mailto:material...@googlegroups.com] On Behalf Of rafique naik
Sent: Monday, February 09, 2009 1:16 AM
To: material...@googlegroups.com
Subject: [MW:1518] Significance of HOT PASS

 

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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[Armstrong, Joel]

I would say no, but keep in mind that some welders call the "hot pass" the weld pass after the root pass.

Joel Armstrong
J3 Welding Services, LLC
President

________________________________

From: material...@googlegroups.com on behalf of rafique naik
Sent: Sun 2/8/2009 11:16 AM
To: material...@googlegroups.com
Subject: [MW:1518] Significance of HOT PASS

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[piepe...@kpnmail.nl]

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

[Pieper QSI]

Dear Rafique,

 

I am a certified International Welding Technologist and perform often welding inspections but I never accept to weld root pass only and than stop welding for the night, especially for such small wall thickness and diameter welds.

In my opinion also the most regulations doesn’t accept such.

Your risk for getting cold cracking will become much higher if you do so even for such easy to weld material as A106 grade B. If you still accepted such than I propose NDT in front of welding and pre-heating up to 75 - 125°C in order to avoid any moisture being present on the weld surface because of previous cooling down.

 

Best Regards,

 

Herman Pieper

 

Pieper Quality Support and Inspection

Phone: +31 (0)521 380083

Fax:    +31 (0)84 7539225

Cell:    +31 (0)6 51691215

 

Chamber of Commerce North Netherlands 01136551

VAT NL128062150B01

 

[pjo...@technip.com]

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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