Carbon steel welding consumable are used on SS piping in one of the US power plant. FYI pl.
video link attached here with
http://www.youtube.com/watch?v=w90x2QlhYzw
SALT LAKE CITY -- A huge welding job that went wrong at a PacifiCorp power plant in Wyoming has created concerns about a similar job with the same actors at a Utah power plant.
The problem involved an unknown number of workers for a California contractor who secretly used sub-standard welding procedures. Utah's top boiler safety official says he hasn't ruled out a temporary shutdown at a power plant in Utah because of the same concern.
"We think it was just a few bad actors and they were dismissed." -Dave Eskelsen PacifiCorp officials say the guilty welders were quickly fired and there's no safety issue in Wyoming or Utah. But union officials are upset that PacifiCorp plans to use the same welding contractor on yet another power plant in Utah.
At Wyoming's Jim Bridger power plant, one of the four giant boilers needed an overhaul. So PacifiCorp contracted with California-based PMSI, which put dozens of welders to work. One of them triggered an investigation by alleging widespread cheating.
"There was some truth to the charge that some individual welders were taking shortcuts," said PacifiCorp spokesman Dave Eskelsen. "We think it was just a few bad actors and they were dismissed."
Jim Cooksey, International Brotherhood of Boilermakers The Boilermakers Union is upset that a non-union company got the contract. They set up a demonstration for KSL, showing how PMSI welders should have used stainless-steel welding rods which require elaborate, time-consuming preparations.
Instead, they secretly used carbon-steel rods.
"Which is absolutely a no-no as far as national welding codes. It creates cracks over time," said Jim Cooksey with the International Brotherhood of Boilermakers.
PacifiCorp investigated and PMSI fired some welders -- it won't say how many. The union claims it was between 10 and 16. PMSI also agreed to cut out more than 500 welds, and re-weld the pipes at the company's own expense.
"It just shows me that they are rewarding deceitful behavior." -Jim Cooksey "All indications are that it was not condoned by the contractor, that it was a few individuals making poor decisions," said Eskelsen.
Cooksey has another idea. "I don't know if I can say this, but I'd say that's BS because our inspector working for PMSI said basically this is a standard operating procedure," he said.
PacifiCorp spokesman Dave Eskelsen
The same welders allegedly did the same thing last spring when they refurbished the Hunter plant near Castle Dale. Utah's chief of boiler safety, Pete Hackford, hopes to avoid a shutdown of the Hunter plant. He's asked PacifiCorp for a plan by early next week.
"A plan on how they're going to remedy this and fix this and bring it back to code," Hackford said.
Meanwhile, PacifiCorp has angered the union by using PMSI again next month at the Huntington power plant.
"It just shows me that they are rewarding deceitful behavior," said Cooksey.
But PacifiCorp is defending its use of PMSI. "They do quality work and they have stepped up when notified of this error," said Eskelsen. "They have dismissed the offending welders and they have agreed to make it right."
PacifiCorp officials believe it's true that improper welding was done at the Hunter plant, but they can't test the welds without shutting down the boiler -- a very expensive proposition.
The next time it's shut down for other reasons, PMSI has agreed to replace all the welds for free. PacifCorp says it won't cost rate payers anything.
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of george.dilintas@gr.bureauveritas.com
Sent: Friday, July 09, 2010 4:03 PM
To: materials-welding@googlegroups.com
Cc: Materials & Welding
Subject: Re: [MW:5915] Re: Dilution cracking
I disagree,
the cracking occurs because a brittle phase is formed at around 800 deg C.
This is expressed by the FN number which has to be above 5.
We avoid the hot cracking by using electrodes with higher Cr and Ni content (309 type)
Dr. G. Dilintas - Authorized Inspector Supervisor
I&F Regional Technical Manager
Bureau Veritas Piraeus - Greece
Tel: +30 210 40 63 113/4
Fax: +30 210 40 63 118
Cell: +30 69 44 64 62 04JASPAL SINGH <jaspaldhesi@gmail.com>
Sent by: materials-welding@googlegroups.com 09/07/2010 13:12
|
|
Dear Ankur,
This is with reference to your clarification on cracking when welding
carbon steel on SS.
In metallurgy there is concept of solubility means all the components
having limited solubility with respect to each other. Like in SS 304.
Cr is ~ 18 to 21% and Ni 8-10%. Any composition below or above this
will not meet the required mechanical properties because of solubility
issue.
For example:
Welding of Carbon Steel on SS with SMAW(bead on plate):
CS chemistry: Fe + small other elements
SS 309: 21% Cr + 12% Ni
Composition of weld metal with 35% dilution : Cr= 6.4% , Ni = 3.1%
Fe=93%. Which is unknown chemistry even Cr and Ni do not want to mix
with each other at this level. So cracking occur during
solidification.
On the other side while welding on Carbon Steel with SS
The resultant chemistry will be : Cr will be 17 to 18 % Ni in the
range of 8 o 10 % which is chemistry of known composition (SS304)
having perfect solubility, so no cracking .
This is the basic phenomenon of cracking while we are welding CS on
SS. You can refer any metallurgy book for behavior of elements during
solidification.
Regards
Jaspal Singh, CWI-AWS, CSWIP-3.1
Assistant Manager – Quality Assurance
Process Equipment Division
ISGEC, Yamuna Nagar, Haryana -135001
Phone: 911732307251
Ext: 251 Mb: +91 9996624244
On 9 जुला, 12:07, "Welder's Helper" <vettaikkaran2...@gmail.com>
wrote:
> Welding of stainless steel with carbon steel electrodes results in formation
> of martensite structure which is prone to cracking under stress or it may
> crack immediately during welding depending upon the welding conditions,
> thickness of the part being welded, deposition of consumable etc. But in
> actual practice, cracks do not come up always. Many a times, welders weld
> the stainless steel piping with carbon steel in order to avoid the need of
> purging and they successfully make the weld without any defects that can be
> picked up in radiography. They weld the root pass with carbon steel
> consumables and the rest of the welding is made in SS consumable.
>
> However, welding of stainless steel with low alloy steel electrodes would
> definitely come up with cracking as it is more susceptible to cracking than
> carbon steel consumables. Same martensite structure formation would occur
> and LAS consumable being used without any preheating protocol would crack
> itself during welding mainly due to uncontrolled cooling.
>
> Both of the situations can be seen visually during inspection and one can
> say that carbon steel or LAS consumable has been used but if gone
> un-inspected then one may not get it picked with radiography especially in
> the case of carbon steel consumable, however, LAS consumable has pretty
> higher chances of getting cracked and picked up.
>
>
>
>
>
> On Thu, Jul 8, 2010 at 10:09 PM, Ankur Mande <prince.an...@gmail.com> wrote:
> > Hello friends,
>
> > I have just joined this wonderful & group with "active members". I
> > have one query. Please let me know as to why we observe cracking when
> > carbon / low alloy steel is accidently welded on stainless steel. If
> > any body has any backup or paper related to this, request you to post
> > it.
>
> > Regards,
>
> > Ankur Mande.
> > 09925027848
>
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>
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