Saturday, April 24, 2010

[MW:4944] [MW-4939] FCAW welding for pressure part

 

Mr. Shashank,

 

FCAW has some limitations no doubt, as every welding process does. However if one know the process then  good results are achievable. Typically:-

 

the advertised benefits of FCAW were:

          High quality weldments,

          Increased tolerance for scale and dirt when compared to GMAW

          Higher deposition rates when compared to manual processes(SMAW)

          Multi-position potential

          Optimization of weld joints thru active flux alloying

          Good Bead Appearance

          Better penetration than obtainable from SMAW

          Smooth, Stable Arc

 

Common problems

          Undercutting

          Incomplete joint penetration

          Porosity

          low impact (CVN) test results

          local brittle zones in weldments HAZ

          reheat cracking in 300 series stainless steels

          poor wire quality (incomplete filling)

          lack of small diameter wires

          lack of fusion (need to stay on leading edge of puddle was not appreciated, leading to LOF)

 

I have seen that oil  refineries / owners allowing  FCAW for pressure parts,  however calls for a lot more control, due to propensities of defect. However note  defects in gas shielded process could be due to many factors. Some examples are cited below from the welding specifications of various large oil giants:-  

 

 

1.      A North American Oil Giant (Largest in the world):- Flux cored arc welding (FCAW) either with or without external gas shielding may be used for either groove or fillet welds. For pressure boundary welds and welds with impact test requirements, only electrode classifications or types which are identified as multipass and which have specified minimum impact test requirements shall be used.

 

2.      Large Oil Giant from Middle East :-Flux-Cored Arc Welding (FCAW).—

 

         The FCAW process shall not be used for the root pass on full penetration, groove joints that are welded from one side only without backing (backing may be used if it is removed after welding).

         Self-shielded FCAW shall not be used without the specific approval of owner. FCAW electrode shall be restricted to the specific brand, type, and maximum size as used for the PQR.

 

3.      Another  Larger Oil Company in North America (Now part of the largest  Company as under 1):-

 

The flux cored arc welding process(FCAW) may be used, subject to owners review & approval. Proposal to use FCAW must be submitted prior to order placement, provided:-

 

1.      Gas shielding is used

2.      Material to be welded is carbon steel or for application of weld overlay on carbon steel or low alloy steel.

3.      The FCAW process is not "short arc".

4.      The FCAW process is not used for the root pass in single sided welding.

5.      Production consumable are restricted to the manufacturer and grade qualified.

6.      Only EXXT-1 or EXXT-5, (flat or horizontal position only) welding wires are used.

7.      Service is not hot hydrogen (over 2600 C--500 0F), wet hydrogen sulphide or  hydrogen fluoride.

8.      Primary flange rating is class 300 or lower.

9.      At  least five percent of the individual welds are 100% radiographed or ultrasonically tested

10.  Ten percent of the nozzle-to shell or head welds (including at least one of each size) shall be 100% radiographed or ultrasonically examined.

11.  For all other applications not meeting the above conditions, FCAW process may be considered on a case-by case basis. The review will include the evaluation of the specific application, verification of fabricator's experience, additional qualification and/or NDE requirements and  owners witnessing of welding procedure and/or welder qualification.

 

 

Generally due to past records of this process many clients provide conditional acceptance and additional NDE. But the process, equipments, consumables, gases have improved leaps and bounds in last 2 decades, and with availability of skilled welders, this process helps the fabricators a lot and is lot reliable than before. For pressure vessels  this process would give  good reliability with premixed mixed gases (Ar+CO2, Ar+O2) from good suppliers .Refer AWS-SFA 5.32, specification for shielding gases for good selection criteria.

 

I hope this would be some food for thoughts. If you have access to NACE , you may download the  attached article, which is very informative.

 

Thanks.

 

Pradip Goswami,P.Eng.

Welding & Metallurgical Engineer/Specialist

Ontario Power Generation Inc.

Email-pgoswami@sympatico.ca,

pgoswami@quickclic.net

 


From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Shashank Vagal
Sent: Friday, April 23, 2010 3:44 AM
To: materials-welding@googlegroups.com
Cc: Shamesh Lotalikar
Subject: RE: [MW:4939] FCAW welding for pressure part

Can anyone explain to me why one goes for FCAW - manual? As I see it, it is intended for automated welding (like SAW). But then again, while SAW is relatively safe and efficient mode of welding, FCAW seems to plentily flawed.   So, why FCAW? And if it HAS to be FCAW, what are the pros and cons - meaning how to get the best out of it?

--- On Thu, 22/4/10, BHARAT GOLE <bharatgole@hotmail.com> wrote:


From: BHARAT GOLE <bharatgole@hotmail.com>
Subject: RE: [MW:4927] FCAW welding for pressure part
To: "Material Welding" <materials-welding@googlegroups.com>
Date: Thursday, 22 April, 2010, 3:56 PM

Its true that LOF is not easy to detect by RT if its not preferentially oriented. But no NDT method can be replaced by other since each method has its own advantage & disadvantage over each other. So decision of change of RT with UT is depend on so many other factors such as time, economics, skill, retention of records and last but not least recommendation of code of construction.

Bharat B. Gole

 


Subject: Re: [MW:4917] FCAW welding for pressure part
From: george.dilintas@gr.bureauveritas.com
Date: Thu, 22 Apr 2010 09:58:11 +0200
To: materials-welding@googlegroups.com

The new UT techniques are more accurate than RT


  From: "sachin sankhe" [sachin.sankhe@rediffmail.com]
  Sent: 22/04/2010 06:12 GMT
  To: <materials-welding@googlegroups.com>
  Subject: [MW:4915] FCAW welding for pressure part


Hi,

We`have FCAW welding for pressure part in refinery service

As FCAW welding mainly have discontinuities like incomplete fusion

So we have specified 100 % RT/MP/DP
However UT is more preferred over RT for planar defect due to incomplete fusion
I feel 100 % RT to be replaced by 100% UT

Request you to give your opinion
Regards
Sachin.Sankhe

http://sigads.rediff.com/RealMedia/ads/adstream_nx.ads/www.rediffmail.com/signatureline.htm@Middle


--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to materials-welding-unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.

--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to materials-welding-unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.


The latest auto launches and test drives Drag n' drop

--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to materials-welding-unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.

 

--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to materials-welding-unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.


THIS MESSAGE IS ONLY INTENDED FOR THE USE OF THE INTENDED RECIPIENT(S) AND MAY CONTAIN INFORMATION THAT IS PRIVILEGED, PROPRIETARY AND/OR CONFIDENTIAL. If you are not the intended recipient, you are hereby notified that any review, retransmission, dissemination, distribution, copying, conversion to hard copy or other use of this communication is strictly prohibited. If you are not the intended recipient and have received this message in error, please notify me by return e-mail and delete this message from your system. Ontario Power Generation Inc.

No comments:

Re: [MW:34832] Inquiry about Single Bevel with Back Grinding

Dear Uday, As per your question that one is called with backing only,Simple both side you are welding it is backing with strip or without st...