A welding procedure is a method of controlling the welding process.
Purpose of procedure:
1) To confirm a joint can meet design procedure uniformity
2) Instruction for welder
3) Ensure repeatability
Weld procedures are approved to make sure they are efficient and execute the physical and mechanical properties necessary to reach the required standard (to establish the essential variables for contractual obligations).
Welders are approved to guarantee a particular welder is capable of welding to a procedure and obtaining a result that meets specification.
The task of collecting the data and drafting the documentation is often referred to as ‘writing’ a weld procedure. In many ways this is a fateful term as the writing of documents is the last in a series of tasks.
Producing a weld procedure involves;
Planning the tasks
Collecting the data
Writing a procedure for use or for trial
Making test welds
Evaluating the results of the tests
Approving the procedure of the relevant code
Preparing the documentation
In every code reference is made to how the procedures are to be devised and whether approval of these procedures is required. In most codes approval is compulsory and tests to verify the skill of the welder are specified. Details are also given of recognition criteria for the finished joint.
The move toward used depends on the code, for example:
BS 2633 (Class 1 arc welding of ferritic steel pipe work for carrying fluids) give general information on various aspects of a appropriate weld procedure.
AWS D.1.1 (Structural welding code - steel) provide more detailed instructions for different joints and processes that are, in effect, pre-qualified procedures.
Other codes do not deal particularly with the details of the weld procedure but refer to published documentation, e.g. BS 5135 ‘procedure of arc welding carbon and carbon manganese steels’.
COMPONENTS OF A WELD PROCEDURE
Items to be included in the procedure can be some of the following:
- Thickness (for pipe this includes outside diameter)
- Surface condition
- Identifying marks
- Type of process (MMA, TIG, SAW etc.)
- Make, brand, type of welding consumables
- When proper, the temperature and time taken for drying and baking of electrodes
and / or consumables
- Welding position
- Edge preparation
- Method of cleaning, degreasing etc.
- Fit up of joint
- Jigging or tacking procedure
- Type of backing
- Whether shop or site weld
- Arrangement of runs and weld sequence
- Filler material, composition and size (diameter)
- Welding variables - voltage, current, travel speed
- Weld size
- Back gouging
- Any specific features, e.g. heat input control, run-out length
- Preheat and inter pass temperatures including technique and control
- Post weld treatment including technique and control
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