Weld Repair and the Importance of Analyzing Failure Mode
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EDITORIAL
Weld Repair and the Importance of Analyzing Failure Mode Daniel J. Thomas
Submitted: 8 February 2016 / Published online: 22 February 2016 Ó ASM International 2016
At any time in industry, when a weld fails in any critical component, this usually results in loss of production or in extreme cases a shut down altogether of the production process. When this happens, typically we look for the fastest way to repair the system in order to put it back into service. The pressure is on to fix the weld, quickly and efficiently. However, when we consider that weld failure happens because of numerous reasons, is it not more important to find out why it has failed in the first place? And subsequently using this knowledge will prevent that weld from failing again. On-site welding processes are very important across heavy industry. The most commonly used processes used on site are shielded metal arc welding (SMAW) and manual metal arc welding (MMA). Welding in industry is D. J. Thomas (&) College of Engineering, Swansea University, Swansea, UK e-mail: [email protected]
often carried out in exposed cold conditions, in winds and sometimes even in the rain. These environmental factors can make welding very challenging. I have an appreciation of this, having previously worked in the steel manufacturing and power generation industries as an on-site engineer. We often carried out SMAW welding up to 100 m off the ground, welding dreaded high-silicon content steel plates together in atrocious conditions. Trying to control the arc and weld pool becomes almost impossible when the wind is howling, as it often is here in Wales. In conditions like this, the types of welding electrodes, current, and weld position become critical. Departure from these standards can result in the wrong degree of heat being introduced into the workpiece, which can subsequently cause fracture some years down the line. When welding, it is easy to lose concentration of the weld pool and to produce an undercuts or incomplete penetration. Wind can affect the gas flow (SMAW) with air contaminating the weld, which can cause porosity. There are so many other factors that can significantly weaken the weld, which will result in premature failure. There are numerous other reasons why weld failure happens. The key reasons why welds fail prematurely in services are 1. The material and its chemistry properties. 2. Inappropriate weld specification during the design process. 3. Defects resulting from the welding processes. 4. Excessive unanticipated service conditions. The investigation process following weld failure is critical. Often, the personnel first on the scene will not necessarily be trained in the science of failure analysis. However, some investigative steps should always be taken. It is important to ensure that nothing is moved, reassembled, or repaired prior to the failure investigation. Document the condition
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of the weld and surrounding parent material when the failure was identified. Write down all the external factors that may have h
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