Hence GMAW/FCAW is mostly restricted to overlay applications and not pressure parts in ASME Boiler and Pressure vessel fabrication as the risk factor involved is high.
Regards
Prem S Nautiyal
Cell: 9769316004 / 9004063879
On Tue, 05 Jul 2011 08:51:37 +0530 wrote
>
Mr Thakkar,
I would like add a few more notes on this chain of
responses. To start with your query is not to the point.
Which GMAW technique you have in mind ?. GMAW although accepted
asa very good welding processes, have it's own limitations.
TraditionallyGMAWhave the
following variations:-
Short
circuiting (GMAW-S).
Globular (GMAW-G);
Pulsed (GMAW-P),
Spray
(GMAW-Sp),
The first2 techniques(GMAW-S and GMAW-G) are really NO-GO for BPV fabrication, reasons :
Short Circuiting Arc-Good for thin sections, frequent chances of
lack of fusion, excessive spatter depending on the materials being
welded.
Globular-Higher spatter levels result in costly cleanup Prone to
cold lap or cold shut incomplete fusion defects
On the other hand:
Spray-Reliable technique, but difficult to control with
straight GMAW process, works well with Pulsed Mode
GMAW-P-Accepted by the industry widely. Some additional notes
in API-582 areas follows:-
GMAW-P-may
be
used for any
material thickness In any position. Welding
shallbe performed with the same
make
and model of welding
equipment using the same program settings
asthose
used in the
procedure
qualification.
The latest state
of art techniques for GMAW is based on waveform technology, such as Lincoln STT
or MilerRMD.. ASME Sec-IX,2010 has added quite a bit of description on this
technique. Look in Appendix-H . Although non mandatory thisappendix
explains the prosand cons of waveform technology both from procedure and
performance qualifications angle.
GMAW-P or Non- Pulsed
based on waveform technologyis considered to be most reliable and
consistent. However for single sided full penetration joint there could be always ifs and buts, and possible additional NDE
requirements from the clients. This technique had been
used extensively and with success for high pressure piping in power plant and
oil refineries to perform single sided full penetration welding but for pressure
vessels still there are
skeptisms.
ASME BPV design is
traditionally based on CAT,A,B.C, D joints. For thick-walled vessels SAW is the prime welding technique for all
fabricators.ForCAT-A,B joints no-one would risk any lack of
fusion defects in the root passes. If the WPS is established with
GMAWat the root pass followed by SAW, every welding QA plan would call for
a sound welmetal at the root If the sound root could be established
with or without back-chipping (for GMAW) with
100% consistency, then you may apply the same at the discretion of
the project specifications.
If the vessel
thicknesses are less than 1" wall I would say thickness (typically 3/4") and
smaller diameter typically less than 1 meter dia,use of GMAW-P ,
Lincoln STT or Miller RMD would be a good qualityoriented welding
process, provided good welder/operators training is done.However to
get the consistently good production weld quality levels additional NDE(
UT) should be mandated.
Thanks.
Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
& Consultant
Ontario,Canada.
Email-pgoswami@sympatico.ca,
pgoswami@quickclic.net
From: materials-welding@googlegroups.com
[mailto:materials-welding@googlegroups.com] On Behalf Of arijoy
roy
>Sent: Friday, July 01, 2011 7:44 AM
>To:
materials-welding@googlegroups.com
>Subject: Re: [MW:11565] GMAW
application restriction
>
>
I am from an industry manufacturing hydraulic excavators.
We use GTAW extensively for welding high pressure line pipes with
end flanges . Pressure upto 350 bar. The joints are but joints without
back up strip
>
>
>
>--- On Thu, 30/6/11, praveen alavandar
>
>From:
praveen alavandar
>Subject: Re:
[MW:11548] GMAW application restriction
>To:
materials-welding@googlegroups.com
>Date: Thursday, 30 June, 2011,
6:02 PM
>
>
Hi,
If you application invloves welding of pipes (Where back
chipping is not possible), there are two options for welding the
root pass.
1. Use electrodesE 6010 or E 7010 (cellulosic
Electrodes) or E 7016-1 for non critical lines (e.g., lines other
than compressor suction / inlet lines).
2. UseSTT (Surface Tension Transfer) Process for root
pass,it is similar to GMAW short circuit transfer mode of
metal transfer. You'll need to properly set the welding parameters
to avoid any LOF, but once your welders are well trained, you can
really see the productivity. Please note that some clients still
have a restriction on using this process.
If you application involves fabrication of pressure vessels,
where you have enough access for back chipping the root pass, and
you wish not to do so, then SAW is a good option.
The joint preparation shall be such that the root face or the
land should be long enough to prevent any burn though when welding
the root pass, in addition to that you'll have to have tight butt
joint (i.e.,) no root gap at all.
After completion of one side, weld the other side (without
back chipping) with SAW process, you parameters should be such
that you have good cross penetration (engulfing the lan or root
face) thus giving you a full penetration butt joint without the
need for back chipping.
Hope this helps.
Regards,
Praveen Alavandar
>
>--- On Thu, 6/30/11, rajeev arora
>
>From:
rajeev arora
>Subject: Re:
[MW:11538] GMAW application restriction
>To:
materials-welding@googlegroups.com
>Date: Thursday, June 30,
2011, 4:14 PM
>
>
there is electrode , which is having good
penetration power i.e. E7010 , get check with the
manufacture
>
>
On 30 June 2011 17:39,
Maulik Thakkar
wrote:
>
Dear,,
With out chip back. I want the process which can replace
slower GTAW for single sided full penetration joint with out
any chip back
>
>
On Thu, Jun 30, 2011 at
3:55 PM, rajeev arora
wrote:
>
SMAW
>
>
On 30 June 2011 17:05,
Maulik Thakkar
wrote:
>
Is there any option of GTAW
for root runto be carried out inpressure
vessel welding?
>
>
On Thu, Jun 30, 2011
at 2:20 PM, AVA
>
There is
no limitation for GMAW in ASME code. But pay
attention that some of gas cavities made in weld metal
that are acceptable according to codes, but it's make
may risk for hydrogen induce. Then this process is
commonly used for structural equipment's, not in
pressure parts.
Regards
A.V.
From: materials-welding@googlegroups.com
[mailto:materials-welding@googlegroups.com]
On Behalf Of Dinesh Somwanshi
>Sent:
Thursday, June 30, 2011 1:06 PM
>To: materials-welding@googlegroups.com
>Subject:
Re: [MW:11528] GMAW application
restriction
generally GMAW is used for the
filling & capping only.generally the amout of heat
produced in this process also there will be chances of lack
of fusion at the edges ( fusion boundaries ) the torch cup
also makes sometimes for welding in the joint.But this
process limited to only low pressure . You can follow with
the s maw root & hot ,followed by remaining g maw .
>
>regards
>
>dinesh
On Thu, Jun 30, 2011 at 9:57
AM, Maulik Thakkar
wrote:
Dear
All,
Why GMAW
is not widely used for single sided full penetration joints
(with out chip back) for pressure vessel industrial
applications?
Is there
any problem regarding to penetraiton or lack of fusion? I am
confusing. Request you to give technical
answer.
--
>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
thnt eir 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.
--
>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.
>
>
>--
>
Regards,
Maulik H. Thakkar
Larsen & Toubro,
Hazira
>
--
>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.
>
>
>--
>Regards,
>
>
Rajeev
Arora
>0066-854490697
>0066-818706419
>
>
>
>
>
>
>
--
>
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.
>
>
>--
>
Regards,
Maulik H. Thakkar
Larsen & Toubro,
Hazira
>
--
>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.
>
>
>--
>Regards,
>
>Rajeev
Arora
>0066-854490697
>0066-818706419
>
>
>
>
>
>
>
--
>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.
>
--
>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.
>
PREM S NAUTIYAL
CELL : 9769316004
 |
Treat yourself at a restaurant, spa, resort and much more with Rediff Deal ho jaye! --
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.
No comments:
Post a Comment