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Welding Procedure 2
- Thread starter alex18
- Start date
TheBlacksmith
Mechanical
-
1
- #3
Do you mean a pre-qualified welding procedure or a weld procedure specification?
Most codes require that a manufacturer qualify his own procedures, however some codes permit the use of AWS pre-qualified procedures under certain circumstances.
Regards
John
Most codes require that a manufacturer qualify his own procedures, however some codes permit the use of AWS pre-qualified procedures under certain circumstances.
Regards
John
-
1
- #4
Hi there,
Welding is considered a "special process" by all quality management systems. As such, welding requires procedures to control the process and certified technicians to perform the process. This is because the only way to absolutely verify that a given weld will perform mechanically is to destructively test the weldment. Nondestructive tests see some discontinuities but are blind to others. To ensure repeatablity of the process, procedures must be followed. This is good management, too.
American Welding Society recognizes that carbon steel welding procedures are pretty "tried and true". They provide joint parameters, that if followed, will be considered "prequalified" and not require mechanical testing for verification. The welder must stay within the electrical parameters established by the filler metal manufacturer. The joints are very restrictive, and the filler metal electrical parameters are loose. Preheat is important and conservative requirements are also "prequalified" by AWS. Obviously all of this goes to mud if an unskilled technician tries to weld with the procedure.
ASME and other specs require mechanical testing of the weldments to verify suitablity for use. These codes will often permit greater tolerances for the "essential variables" of a welding procedure. Mechanical testing is more expensive, but the greater latitude is often worth it.
Ideally, welding procedures are developed by a company to control their operations to reduce liability and increase shop economy. It is a legal document.
Most groups use welding procedures as a sales tool that sits on dusty shelves in the engineers office to appease customer's auditors.
Develop your own welding procedure in accordance with the applicable Code to fit your needs. Control your process!
Koz
Welding is considered a "special process" by all quality management systems. As such, welding requires procedures to control the process and certified technicians to perform the process. This is because the only way to absolutely verify that a given weld will perform mechanically is to destructively test the weldment. Nondestructive tests see some discontinuities but are blind to others. To ensure repeatablity of the process, procedures must be followed. This is good management, too.
American Welding Society recognizes that carbon steel welding procedures are pretty "tried and true". They provide joint parameters, that if followed, will be considered "prequalified" and not require mechanical testing for verification. The welder must stay within the electrical parameters established by the filler metal manufacturer. The joints are very restrictive, and the filler metal electrical parameters are loose. Preheat is important and conservative requirements are also "prequalified" by AWS. Obviously all of this goes to mud if an unskilled technician tries to weld with the procedure.
ASME and other specs require mechanical testing of the weldments to verify suitablity for use. These codes will often permit greater tolerances for the "essential variables" of a welding procedure. Mechanical testing is more expensive, but the greater latitude is often worth it.
Ideally, welding procedures are developed by a company to control their operations to reduce liability and increase shop economy. It is a legal document.
Most groups use welding procedures as a sales tool that sits on dusty shelves in the engineers office to appease customer's auditors.
Develop your own welding procedure in accordance with the applicable Code to fit your needs. Control your process!
Koz
Koz,
Those pre-qualified procedures (joints) that you reference are only for AWSD1.1. Do not get those misunderstood by Alex18. Those pre qualified joints do not qualify pipe or other code compliant situations. Most welding procedures are qualified for base material thickness, pwht, and other parameters which are not covered under AWS D1.1. Such as would you use a pre qualified procedure under AWS for a B31.3 application? Of course not you need something seperate for that application, service. Alex what type of application are you looking for? Need more input than just a PQR.
Those pre-qualified procedures (joints) that you reference are only for AWSD1.1. Do not get those misunderstood by Alex18. Those pre qualified joints do not qualify pipe or other code compliant situations. Most welding procedures are qualified for base material thickness, pwht, and other parameters which are not covered under AWS D1.1. Such as would you use a pre qualified procedure under AWS for a B31.3 application? Of course not you need something seperate for that application, service. Alex what type of application are you looking for? Need more input than just a PQR.
Moseley,
D1.1 does cover pipe. Pipe prequals use a backup ring and no open root. Open root pipe is qualified by standard pipe splice test and a special test for T, Y, & K connections in accordance with table 4.?.
ASME Section IX has been considering prequals for Carbon Steel for a long time now. Have they ever implemented it?
Most of the AWS Codes, D1.5, D1.4, D1.2, D1.3 have prequalified welding procedures within them. SMAW procedures dominate.
If Alex18 is in the refinery busyness, he is probably working with B31.1, Power Piping. That will tie him back to ASME IX for qualification requirements.
The important thing is that he understand the need for welding procedures. We welders, as artists, have a built-in hubris that says "We know what we're doing. We don't need anyone telling us how to weld." Unfortunately the welding training in our country, with almost no exception, is very poor and in decline. Most welders do not know how to successfully join the duplex stainless, the Carpenter 20, the HY-100, the 4130, the Cr-Mo. All of these materials require significant welding "engineering" (for lack of a better word) to achieve a sucessful weld. And they require constant monitoring by an inspection group to verify the welding is performed in accordance with the tested welding parameters without taking artistic license. You can't cut corners on the above materials, and other fantastic metals that have been developed over the last couple of decades.
Since welding is a "special process" that cannot be 100% verified, cutting corners may build in delayed problems such as reduced tensile strength or corrosion resistance from over-heating the metal, or microfissures from exceeding pass depth limitations that later fail during seismic activity.
And the problem with "canned" welding procedures out of a book or just following the example page or list of essential variables in the Code, is that there are technical ommissions in our welding codes. You can't always control your welding process adequately just following the book. Think about the electrical stick out limitations needed to control our flux core or submerged arc operations. The codes are blind to this important electrical variable. There are other blindspots, but you see my point. The codes have been written by commitees of people using very little statistical testing to back up the requirements. We have codified art.
But written welding procedures are the best thing we have to increase the repeatability of our welding operations. Good welders will jump on the procedure and rip it apart if it doesn't work or too restrictive to meet production's constantly changing environment. That is a good thing.
Over time, the procedure will settle down. Then it becomes a reference tool for the welder. He doesn't need that "Pocket Welder" in his toolbox to tell him amps and volts for the next wire diameter his foreman throws at him. It becomes a management tool because we can see when we are running 5 different shielding gases on the floor or every supplier from Lincoln to Eutectic-Castolin sells us rod. It becomes a training tool for our apprentices reminding them of the good welding practices developed by the company.
Koz
D1.1 does cover pipe. Pipe prequals use a backup ring and no open root. Open root pipe is qualified by standard pipe splice test and a special test for T, Y, & K connections in accordance with table 4.?.
ASME Section IX has been considering prequals for Carbon Steel for a long time now. Have they ever implemented it?
Most of the AWS Codes, D1.5, D1.4, D1.2, D1.3 have prequalified welding procedures within them. SMAW procedures dominate.
If Alex18 is in the refinery busyness, he is probably working with B31.1, Power Piping. That will tie him back to ASME IX for qualification requirements.
The important thing is that he understand the need for welding procedures. We welders, as artists, have a built-in hubris that says "We know what we're doing. We don't need anyone telling us how to weld." Unfortunately the welding training in our country, with almost no exception, is very poor and in decline. Most welders do not know how to successfully join the duplex stainless, the Carpenter 20, the HY-100, the 4130, the Cr-Mo. All of these materials require significant welding "engineering" (for lack of a better word) to achieve a sucessful weld. And they require constant monitoring by an inspection group to verify the welding is performed in accordance with the tested welding parameters without taking artistic license. You can't cut corners on the above materials, and other fantastic metals that have been developed over the last couple of decades.
Since welding is a "special process" that cannot be 100% verified, cutting corners may build in delayed problems such as reduced tensile strength or corrosion resistance from over-heating the metal, or microfissures from exceeding pass depth limitations that later fail during seismic activity.
And the problem with "canned" welding procedures out of a book or just following the example page or list of essential variables in the Code, is that there are technical ommissions in our welding codes. You can't always control your welding process adequately just following the book. Think about the electrical stick out limitations needed to control our flux core or submerged arc operations. The codes are blind to this important electrical variable. There are other blindspots, but you see my point. The codes have been written by commitees of people using very little statistical testing to back up the requirements. We have codified art.
But written welding procedures are the best thing we have to increase the repeatability of our welding operations. Good welders will jump on the procedure and rip it apart if it doesn't work or too restrictive to meet production's constantly changing environment. That is a good thing.
Over time, the procedure will settle down. Then it becomes a reference tool for the welder. He doesn't need that "Pocket Welder" in his toolbox to tell him amps and volts for the next wire diameter his foreman throws at him. It becomes a management tool because we can see when we are running 5 different shielding gases on the floor or every supplier from Lincoln to Eutectic-Castolin sells us rod. It becomes a training tool for our apprentices reminding them of the good welding practices developed by the company.
Koz
Article V of Section IX explains what is required in order to use prequalified welding procedures. They are referred to as Standard Welding Procedure Specifications. (SWPS) They were developed by the Welding Research Council, and Section IX does not allow you to deviate or modify the procedures in any way. So the application has to fit the SWPS exactly, or you are back to qualification the old fashioned way. (The way I always end up having to do it)
Koz,
Even though the SPWSes were written by the welding research council, I believe they are published by AWS, so we could be talking about the same ones. I don't think that the SWPSes will ever really fit my needs either, but I can see how they might be handy for someone who doesn't do much Section IX work.
Even though the SPWSes were written by the welding research council, I believe they are published by AWS, so we could be talking about the same ones. I don't think that the SWPSes will ever really fit my needs either, but I can see how they might be handy for someone who doesn't do much Section IX work.
Koz or GRoberts or any interested party:
Can you address the following comment as it pertains to cross country pipeline welding.
"Corrosive failure at weld joints due to galvanic effects arising from local gradients in steel structure (i.e., changes in material composition and structure at the welds) are well-known."
My field experience in construction and operation of new, or modern, pipeline systems doesn't support the statement. Particularly when pipe metallurgy, weld materials, application of field joint coatings (in this case FBE) and procedures are well controlled.
Thanks
Can you address the following comment as it pertains to cross country pipeline welding.
"Corrosive failure at weld joints due to galvanic effects arising from local gradients in steel structure (i.e., changes in material composition and structure at the welds) are well-known."
My field experience in construction and operation of new, or modern, pipeline systems doesn't support the statement. Particularly when pipe metallurgy, weld materials, application of field joint coatings (in this case FBE) and procedures are well controlled.
Thanks
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