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Up Topic Welding Industry / Inspection & Qualification / Welding of stainless steel to alloysteel
- - By khodabandeh (**) Date 09-27-2005 14:31
Dear Sir,
In offsite piping of power plant project the contractor has shortage of materials in steam piping lines, for this reason it was decided to use the stainless steel matrerials in continuation of the alloy steel materials. I have these guestions :first,if the temperature of the service is more than 400 degrees centigrade, is that dangerous for creation of the chromium carbide precipitation?second,which one is more suitable ,filler wire ER309L or 309LMo?
Parent - - By - Date 09-27-2005 15:09
First of all, what grade of alloy steel are you tieing into and what grade of stainless steel are you planning to use to make this tie in? If the service is going to be above 400C for an extended time, you will very likely encounter sensitzation (chromium carbide precipitation) if you are using a 309L or 309LMo as a filler. The low carbon grades are recommended for slowing the rate of sensitization in normal welding cycles, but at extended tiimes above 400C, at some point you will very likely encounter sensitization.
Parent - - By jon20013 (*****) Date 09-27-2005 15:39
Good questions Chuck.

Add in a question of WHO made the decision as that is the person or party this question should be addressed to.

Sorry if I sound a little sarcastic, it is certainly not directed at you Chuck, but this is a design issue and really shouldn't be placed here for anything other than VERY generalized answers.
Parent - By - Date 09-27-2005 16:10
Jon,
You never sounded sarcastic at all. No need to worry about that. I know you too well to think anything like that. You are 100% correct about this being a design issue and I would only give my answers based upon information that is accurately given to us. At this point, I (we) do not have enough accurate information to give recommended advice. Thank you for making a good point on that. All should realize that, due to liability risks, we are only giving recommended "advice" and not directives. Any final decisions made regarding any information in these forums should be thouroghly researched to make sure it fits the applications encountered. It is also very important that accurate and thorough information is given to us when asking for advice.
Parent - By billvanderhoof (****) Date 09-28-2005 07:47
Of course the person who made this decision (or his superiors) will ultimately have to recind it. I suspect though that the questioner may be trying to gather some authoritive comments so that his presentation will not be dismissed out of hand.
Bill
Parent - - By khodabandeh (**) Date 09-28-2005 09:41
Dear Sir,
The specification of alloy steel material is A335 garde P11 has been welded to stainless steel materials with A312 Type 316L specification.
Parent - - By - Date 09-28-2005 11:01
Sir,
With all due respect, this question should be put before the Engineer that decided to use stainless steel to tie into the 1 1/4 Cr-1/2 Mo material instead of buying the correct material to continue the job. There are so many things that need to be considered before just saying, "Will a 309L or 309LMo be best". You are using two totally different grades of steel with two totally different metallurgcal characteristics. It appears that you are using the stainless steel to continue the pipe run just because it is handy. That is not a good judgement to use "convenience" as an excuse to use a grade of steel, especially in a power plant. You are asking us for recommendations...well, my final recommendation is to go out and buy the correct material and do the job right. You are only asking for trouble when you start substituting these two different grades of steel without considering all of the other metallurgical considerations other than just what filler metal used to weld them. Personally, this is the best I can do considering the information we have been provided with. This is not a decision that should be decided over a welding forum. Your Engineering and Design Dept. needs to be the decision makers on this.
Parent - - By jon20013 (*****) Date 09-28-2005 12:10
Chuck, you are absolutely correct and I believe all of the responders stated some degree of concern about the approach that has been taken by the contractor mentioned by khodabandeh.

Khodabandeh has stated that "the contractor has shortage of materials in steam piping lines, for this reason it was decided to use the stainless steel matrerials in continuation of the alloy steel materials."

In my experience, this has NEVER been a decision any contractor could make without first obtaining concurrence from the Owner's Engineering Department.

If this has already been done then khodabandeh, in my opinion, is simply wasting the time of those HIGHLY talented and knowlegable people who have diligently provided him with a broad spectrum of scenarios and concerns, all seemingly bad.
Parent - By jon20013 (*****) Date 09-28-2005 14:26
In addition to what I said above, seeing how this is a power plant and involving steam lines with the original materials specified as A335 grade P11, now welding to SA240 Type 316L, it's very likely given the application that the ASME Boiler and Pressure Vessel Code may apply.

A335 Grade P11 is an ASME Section IX P4 material (1.25% chrome) welding to an ASME Section IX P8 material. I would nearly bet my bottom dollar that there wasn't a new WPS qualified for this work.

khodabandeh, please confirm if this is correct.
Parent - By - Date 09-28-2005 14:31
These are very good points, Jon. It seems like here lately we (this Forum) are receiving posts that are not necessarily beyond our expertise, but beyond our realm of responsibility. Due to liability, both to us and to the AWS Forum, we need to be careful who and how and IF we answer some questions. I would hate to have someone contact me, or any of us, and have someone say " Well, Chuck or Jon told me this or told me that" without knowing the full and thorough circumstances of the question. It's different if someone asks us "what do you use to weld a 316L base metal", but to start getting into scenarios that involve design and other circumstances that we have no idea on why and who is sort of risky. In my capacity with Avesta I have to be very careful to only recommend standard practices, and not give directives like "you should do this or you should do that", but only offer recommended advice and have the ability to back it up with proven written documentation. I've said enough.
Parent - - By khodabandeh (**) Date 09-28-2005 14:35
With all due respect,I should say that the contract in this project is EPC, therefore according to contract, the contractor has carried out engineering design of the piping.And welding inspection department reminded the existing problems to the contractor.
Parent - - By jon20013 (*****) Date 09-28-2005 14:52
Although I worry very little from a liability standpoint, either for myself or for the Forum, I do worry that some people will take what we say as authoritative and this could naturally prove problemmatic.

Each of us has sufficient experience, education and resources to probably adequately answer almost any question posed however when design matters come into play, which according to direcion taken could potentially have catastrophic results, we should be very cautious about offering any advice except the most general.

khodabandeh, you say the contractor has design authority (EPC) Engineering, Procurement, Construction then I guess my question is where exactly do you fall in this arrangement?

If you are a welding inspector then my advice is to seek that design approval of the material deviation has been granted (with the approval of the Owner), secondly look to see if the welding procedures have been properly qualified. If both of these turn out to be good then continue your inspections, if not, document on a nonconformance report.

On the other hand, if you are a representative of the owner, you should already know the answers to these questions. Please clarify.
Parent - - By khodabandeh (**) Date 09-29-2005 03:44
Dear jon,
With respect due to you.My answer is YES, I am representative of the owner ,also I am welding engineer ,i.e. welding inspection & N.D.T dept. Manager.I want to take precautionary measure for this decision.
Parent - By jon20013 (*****) Date 09-29-2005 09:32
Thank you for clarifying your position, khodabandeh.

Has the contractor already made the welds?

If not, I think you have seen an adequate concern within the Forum to go to your management with reasons why the contractor's deviation from original design should not be permitted, instead they should complete the project as it was originally designed. Because the contractor has realised a shortage of materials is not reason to change the design and shows poor planning on the part of the contractor. Even in an EPC contract the Owner retains deviation approval, you should know that.

If the contractor has already made the welds, with all due respect, you have failed in your job as it seems the WPS has not yet been submitted. Please keep in mind also that passing the mechanical tests required by the PQR does not mean that the WPS is adequate for all service conditions, which seem to be of primary concern in these discussions.

Speaking from a personal side, if I were the Owners Representative and Welding engineer for this project I would fight this change and require the contractor to properly execute original design materials! One way to begin the fight is to force their engineering department to submit a complete design analysis of the proposed change.
Parent - - By MBSims (****) Date 09-28-2005 23:20
This helps a little with understanding the situation, but more information is needed. Since A335 Grade P11 is a piping material and SA240 TP316L is a plate or sheet material, it sounds as if the "continuation" is either an attachment to the outside of the piping or it is plate material that is rolled and welded to form pipe. For the service temperature you mentioned, we would normally use an Inconel filler or electrode (such as ERNiCr-3 or ENiCrFe-3) to minimize thermal stress issues. I believe you should discuss this with the design engineer, tell them what electrode you propose to use, and ask them to verify there are no concerns with thermal stresses.
Parent - - By khodabandeh (**) Date 09-29-2005 04:04
Dear MBSims,
With respect due to you.I should say both materials are related to piping,also the contractor has decided submit the WPS with ER 309L. & ER309LMo. soon.
Parent - By jon20013 (*****) Date 09-29-2005 09:48
khodabandeh, if the deviation goes forward, the contractor will need TWO new WPS' ~ one for the tie in of the carbon to stainless the other for stainless to stainless.

In my experience, the suggested filler metals of ER309L or ER309LMo for the SA-240, Type 316L to itself is not a good match of filler metals.
Parent - - By RBeldyk (**) Date 09-27-2005 16:59
This is a significant dsign issue that need to attention of a professional engineer.

Now, having said that ... in addition to carbide formation, here are a couple things that came to mind:

1. One must examine the stresses and strains that are induced due to differing coefficients of thermal expansion. A stress analysis will need to be completed of the piping system (pipe, angers, supports and anchors).

2. Look at the material couples, a galvanized (zinc coated) hanger in contact with an austentic stainless steel pipe at elevated temperature may yield SME (solid metal embrittlement) of the stainless resulting in a catastrophic failure.


As in most cases a quick fix is worse than no fix at all.

Rich

Parent - By - Date 09-27-2005 17:09
Rich,
I agree, but a Welding Engineer should be quite capable to answer any welding related issues. As I said in my response, there are other issues that we need to be aware of than only the ones given in the original post. We can only answer questions that are presented. If the post fails to give accurate and thorough information, he will suffer from that.
Parent - - By G.S.Crisi (****) Date 09-27-2005 20:42
As a complement to all of the answers that have been given so far, when steel will support continuously temperatures above 400 °C for long periods of time, as is the case of the main steam piping in a power plant, it is subjected to creep.
To overcome this, the material should content 0.5 % of molibdenum. It's possible that Kho has already taken this into consideration, but it cost nothing to point it out.
Giovanni S. Crisi
Sao Paulo - Brazil
Parent - - By MBSims (****) Date 09-28-2005 01:15
In addition to creep, don't forget graphitization can be a problem in plain carbon steels at that temperature at prolonged operating times.
Parent - By jon20013 (*****) Date 09-28-2005 10:06
Good answers all the way around in this posting. Obviously a highly precarious situation has been presented and the level of expertise from the responders is highly impressive, a virtual "Who's who" of our welding world!!!
Parent - - By jon20013 (*****) Date 09-28-2005 15:12
Giovanni; I see from the materials now called out by khodabandeh that the A335, Grade 11 does have the .5% molybdenum as you mention but even though the creep concern may be lessened somewhat there remain, at least in my own mind, a number of highly significant factors that are still unknown.

I refer to, and support the responses of Dr. Beldyk and Mr. Meadows as being the best advice; seek answers from professional engineers who are responsible for this project. We can offer very little in this Forum.
Parent - By G.S.Crisi (****) Date 09-29-2005 15:34
You're right, Jon. I just wanted to call Kho's attention so as not to forget creep among his considerations.
When I put my posting, the alloy material was still unknown to us.
Giovanni
Up Topic Welding Industry / Inspection & Qualification / Welding of stainless steel to alloysteel

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