When the safety and reliability of a component or structure is dependent on the integrity of the welds holding it together, the accepted way of ensuring that this integrity is achieved is to weld to a recognised welding standard.
As a quality control tool, welding standards use a well-established methodology based on the following principles:
- welding is carried out in accordance with a Welding Procedure Specification (WPS)
- the welder undertaking the work is suitably qualified
- the welding is under the control of a welding supervisor
- inspection is carried out at appropriate stages to verify the weld’s quality
An example of fabrication where weld integrity critical is the attachment of the towing eye to a heavy transport draw bar. This is a medium-strength forging of high toughness with a chemistry that provides good weldability.
To ensure its reliable service, it must be welded by a qualified welder strictly following a qualified WPS that involves preheating and a hydrogen controlled welding process.
Qualifying the welding procedure involves the welding of a test piece which is then assessed by visual examination and a macro section. A macro section is a relatively simple method of verifying that the weld is of the specified size, has adequate fusion and penetration, and is free from unacceptable imperfections such as gas pores or slag inclusions.
Achieving the quality of welding required for critical fabrication such tow eyes in an efficient and cost-effective way requires competent personnel. The NZ Welding Centre (a division of the Heavy Engineering Research Association – HERA) provides education and training for those who have responsibility for the supervision of welding, and the qualification of welding procedures and welders.
Upcoming training events in March include a one-week course leading to qualification to Australian Standard AS 2214-2004: Certification of Welding Supervisors – Structural Steel Welding.
This course has been successfully running for three years now and is available in Auckland and Christchurch this year.
In May, a one-day workshop on welding procedures to the widely-used AS/NZS 1554 welding standards will be available in a range of locations around the country.
This is ideal training for designers, engineers, fabricators, welding supervisors, and inspectors who may need to develop, qualify or review the WPS.
For further information:
Tel: 09 262 2885