Welding-procedures:
what to do and how.
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Need and Use of Welding Procedure Specification
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Welding-procedures convey the required information to the workers performing welding operations.
They also assist in controlling workmanship and consistency.
Welding Procedure Specifications (WPS) are detailed welding work instructions.
Their purpose is to explain in words and pictures the whole welding process for any production item.
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Visit also the NEW Page on Process-selection, for
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What are Welding-procedures Specifications?
They are intended to assure correct performance of welding operations each and every time they are applied.
Welding-procedures Specifications are written, binding production documents.
They are uniquely identified by number and revision, dated and signed by responsible professionals.
WPS are kept and updated by strict routines in a central library, much as engineering drawings.
The need for constant use of WPS is generally established and required by Welding Codes as integral elements of quality assurance.
They are useful though also for non regulated work, as a means for imparting education involving discipline.
Effective management should always resort to WPS, and avoid giving verbal instructions or letting welders weld as they like.
Engineering drawings describe exactly what are the finished items in question.
Welding Procedure Specifications explain step by step what has to be done and how, to obtain the sought result.
Acceptable Welding-procedures specifications are clear, understandable and complete.
They do not leave space for personal interpretation of essential instructions.
Only undefined secondary matters of minor technique details can be decided by the worker to the best of his/her understanding.
Tip!: No fear that welders, requested to follow WPS, become robots without will and knowledge.
This is never the case. Welders need all their skill and know-how to perform successful welding time and again.
Welding-procedures specifications typically include the following information:
- Procedure number,
- Reference to the specific engineering drawing and to the detailed operation covered,
- Standard designation and condition of materials, thickness,
- Sketch describing form of joint with dimensions and tolerances,
- Need for preheating or post weld heat treatment,
- Welding jigs and fixtures, tooling, welding position, positioners or special holders,
- Special techniques to minimize distortion,
- Joint fit-up, backing if required,
- Number, position and size of tack welds,
- Welding process, specific welding equipment or type,
- Welding consumables type and size, baking if needed,
- Voltage, Current [AC, DC (polarity) or pulsed (time and curr. levels)],
- Electrode extension (stick-out), torch to workpiece distance, arc length,
- Weld speed,
- Cleaning procedures,
- Inspector approval of weld preparation if needed,
- Welding sequence, number of passes and their order,
- Welding technique details (weaving) if needed,
- Possible back gauging, inter-pass cleaning and grinding stages,
- Interpass temperature if control is to be used,
- Maximum heat input allowed.
Welding-procedures are as simple or as complex as the welding process itself. In particular special precautions are spelled out.
Additional operations required like pre-heating, slow cooling if needed (by what means) or stress relieving after welding (the maximum time interval from end of welding may be prescribed) are detailed with complete description of means and parameters to be used.
A welding procedure is qualified to a given standard when destructive test results of a test piece demonstrate compliance of results with the standard requirements.
The importance of establishing, keeping and following exact Welding-procedures is not only to meet code requirements and ensure repeatability of results.
It also provides a way to investigate possible mishaps and to improve the process if necessary by small and reckoned changes and by strictly monitoring the results.
On possible negative Management attitudes exposing welders to responsibilities they should not bear, I wrote an article titled
Where is the Welding Management?
Click on Management to read it.
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In a previous page on Welding Information, the elements that drawings should include were presented. They specify the technical requirements that guarantee the stability and functionality of the welded assembly.
Welding-procedures specifications presented in this page, prescribe the exact steps in sequence necessary to perform the job successfully. Any additional undefined information, like techniques explained in Recommended Practice documents (see further down), could also be specified there.
A coordinated activity originated by a common initiative of the Welding Research Council (WRC) and the American Welding Society (AWS) has resulted in the publication of a number of prequalified welding procedures, that can be adopted by industry:
ANSI/AWS Standard Welding Procedure Specifications (SWPSs) are intended to meet the rules of the major codes. Single documents differ in processes, base metal and thickness range.
Interested readers can look for what they need (pages 26-27) in the
AWS Publications Catalog Spring 2013, at
http://pubs.aws.org/docs/cat_2013-1_forweb.pdf
AWS published:
ANSI/AWS B2.1/B2.1M:2009
Specification for Welding Procedure and Performance Qualification
Edition: 5th
American Welding Society / 22-Aug-2008 / 300 pages
Some useful links are listed in the following:
AWS - The American Welding Society (http://www.aws.org)
ASM - International (http://www.asminternational.org/portal/site/www/)
The Edison Welding Institute - (http://ewi.org/)
Navy Joining Center - (http://ewi.org/industries/government/)
The Welding Institute - (http://www.twi.co.uk/)
Hobart Institute of Welding Technology - (http://www.welding.org/)
The Welding Research Council - (http://foreng1.securesites.net/wrc/)
Welding Techniques involve details of a welding operation which are controlled by the welder or welding operator within the limitations imposed by Welding-procedures. Optionally Welding-procedures may include specific welding techniques.
Acceptable different welding techniques include the advancement direction of welding which may influence heat input and speed of welding: for simple joining operations the selection of the technique is left to the welder according to his/her preference and experience.
Also the best angles of torch or electrode from the work surfaces and the way of feeding filler metal are details included in the technique, which the welder learn during training and become part of his/her experience to control successfully the outcome of welding operations.
A number of Organizations, most notably AWS (American Welding Society), publish Recommended Practices which address practical aspects of welding processes and are most useful to learn how to improve welding results.
Among them:
- ANSI/AWS C1.1M/C1.1:2000 (R2012)
Recommended Practices for Resistance Welding
American Welding Society / 01-Jan-2000 / 134 pages
- ANSI/AWS D10.10/D10.10M:1999 (R2009)
Recommended Practices for Local Heating of Welds in Piping and Tubing
American Welding Society / 20-Oct-1999 / 113 pages
- ANSI/AWS D10.11M/D10.11:2007
Guide for Root Pass Welding of Pipe Without Backing
Edition: 3rd
American Welding Society / 13-Oct-2006 / 36 pages
- ANSI/AWS D10.12M/D10.12:2000
Guide for Welding Mild Steel Pipe
American Welding Society / 20-Jul-2000 / 49 pages
- ANSI/AWS D10.4-86 (R2000)
Recommended Practices for Welding Austenitic Chromium-Nickel Stainless Steel Piping and Tubing
American Welding Society / 12-Nov-1986 / 44 pages
- ANSI/AWS D10.8-96
Recommended Practices for Welding of Chromium-Molybdenum Steel Piping and Tubing
American Welding Society / 17-Jul-1996 / 20 pages
An Article on Welding Procedure Specifications was published (2) in the Issue 32 of Practical Welding Letter for April 2006.
To read it click on PWL#032.
An Article on Procedure Qualification Record was published (2) in the Issue 33 of Practical Welding Letter for May 2006. To read it click on PWL#033.
An Article on Back to Basics was published (3) in Issue 142 of Practical Welding Letter for June 2015.
Click on PWL#142 to see it.
An Article on Duplex Stainless Filler Metals and Procedure Qualification Problems was published (4) in Issue 152 of Practical Welding Letter for April 2016.
Click on PWL#152.
Tip!: The best welding procedure cannot help a sloppy or inadequate welder to produce successful work, so that there will always be a request and a need for competent and excellent welders.
The following is just an example of software aids available to create and maintain WPS in an organization. No endorsement or recommendation is intended. Other software may be more suitable to different requirements. Interested readers are invited to check on their own.
For information watch the following Videos
Creating AWS D1.1 Prequalified Welding Procedure Specifications
http://www.weldoffice.com/video/pWPS/
WPSAmerica.com Online Welding Procedure Software
https://www.youtube.com/watch?v=5DY2WiG1fl0
ASME Welding Procedure Intro
https://www.youtube.com/watch?v=z748TP7kf_M
Watch the following Video on
How to setup welding test plates https://www.youtube.com/watch?v=h1i7EwCwGFw
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Hardness is important, it should always be known before welding a metallic item, because it can affect the Welding-procedures.
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Welding-procedures, the correct means to convey welding instructions to the welder, to obtain consistent acceptable results. All clearly exposed...
