Weld Procedure: A ‘Cost’ or an ‘Investment’?
- Posted by Neville
- On February 3, 2015
- 0 Comments
When qualifying welders for projects, are we wearing a cost or making an investment?
Where do welders fit in a WPS?
The requirement for Welding Procedure Specifications (WPS) is quite clear under various Australian and International standards, codes, regulations, and in accordance with the client standards. The Welder Qualification is the next step. To apply the relevant and correctly designed WPS, competent welders are the last bastions because if they get it wrong, what is holding the structure together, some unknown material made by electric glue gun?
NDT doesn’t provide a complete picture
Let’s face it, not all welds are examined, and those that are tested by Non-Destructive Test (NDT) methods alone reveal only shape, size and homogeneity. Unfortunately NDT does not answer the question, ‘has the welder deposited acceptably clean material in accordance with the correct WPS’? This is the bottom line issue with Non-Destructive Testing. While it provides a sense of security – the welds are tested – it does not guarantee that the material deposited as a fusion weld is it in accord with the intended design.
Variations between the WPS and the welded material
The deposited weldment design is developed and documented in the WPS as a job instruction for the welder to follow. Should the welder choose to make changes (or make them out of error) to the technique prescribed in the WPS, the deposited weldment (the material, if you like) is simply not as designed and intended in the WPS.
To explain briefly, changes such as:
- class and brand of fillers
- the type and constituents of gas shielding, or
- oxidizing potential across the arc due to arc length,
…will all alter the chemistry of the deposited weldment and if we change chemistry we change mechanical properties.
In the process of making an arc weld we can also add oxidising and nitriding elements that detract from material properties, and we can increase hydrogen level in the deposit. If the welder then makes any changes in the deposition technique, the solidification morphology of the deposited weld metal is altered. This solidification will affect the resultant microstructure, and will change mechanical properties of the deposited weld.
How to we know the weld matches the WPS ?
If we combine these variables, and add for good measure an array of individual human variables, we need to ask:
- Just what have we in that deposited weld?
- What design does it comply with?
- Will it serve the intended design application?
- Can we expect it to fail?
- How do we mitigate that risk?
Hence, the value of the welder qualification process. The welding standard requirements are minimum criteria only. We need to add a knowledge component to describe any technical issues that may affect the intended design, followed by practical exercise in developing the dexterity and skill to manipulate and deposit the weld in the design intended. This is the best way to reduce the risk of unsafe and non-compliant welds.
It’s your legislated obligation
Under the Work Health and Safety Act 2011, business owners and managers have an obligation to train personnel, and have an obligation and duty of care to construct, maintain and operate safe plant. For compliance to the Act, everyone needs to ensure any welds in that plant are safe for the intended design and application by adhering to correctly designed WPS, and carried out by suitably trained and qualified welders.
WPS is a long term investment not a cost.
Rather than a cost, correctly documented WPS records, and welder qualification up-skill training and correct evidential records should be viewed as an investment in long-term plant reliability and safe operation.
AWS Global Advanced Welder Qualification programs
At AWS Global we have developed a series of Advanced Welder Qualification programs for the industry. Hundreds of welders have now completed these programs, and the reduction in repair rates provides an immediate return on the investment into training. Improved weld profile and integrity provides reliability for a longer term for plant items in service, which translates to savings in cost and greater assurance of safety. When the integrity of welded joints are improved, the safety risk is significantly lower for items of critical and hazardous welded plant.
WPS links with your Business’ Risk Mitigation
It follows then that risk is managed and mitigated by improved plant integrity. The consequences of an incident may be mitigated by having trained, competent people conducting any weld task, and of course in place accurate and correctly prepared evidential records.
The astute CEO, PCBU, Engineer, Manager or Supervisor will recognise the value in the comprehensive process of correctly prepared and approved welding procedures, with knowledge and skill based competence for supervisors and welders. The process, when managed correctly, adds real value to mitigating risk, improving integrity and the reliability of any welded items of plant.