First line of defense
Educating welders to achieve quality welds
Good welders learn to inspect their own work, but welders are just one part in a long list of variables (and people) involved in ensuring quality welds. Thorough communication of the welding parameters, as well as proper training to carry out the design, can help welders achieve quality work and to reduce the number of rejected welds.
A welder is just one member of the team required in the production of a product. Every person involved in the welding operation needs to perform his or her own assigned duties, which may include design, materials, processes, and compliance. When there is a weakness in any one of these functions, the welder usually gets blamed for the bad weld.
Welders are under tremendous pressure to produce, and the good ones learn to become inspectors of their own work. Sometimes it is easy for managers to forget that others contribute to the success or failure of a welding operation as much as the welder does.
Every product designer must be trained to recognize a quality weld, and every welder must be trained to recognize the quality of weld that the designer expects. The welder is charged to perform work as instructed by his direct supervisor and, unfortunately, may be at the bottom of the organizational chart hierarchy. In reality, he should be at the top of the organizational chart.
The welder is truly the first line of defense against weld defects, so to help the welder ensure that the weld being performed is up to code, management must provide him with accurate drawings, a copy of the current welding code, customer-approved specifications, and the training required to understand instructions about the type of weld that is expected. A common problem for many welders is not getting adequate instructions about management's expectations. It's vital that management provides an environment that promotes continuous improvement of the welding process in every industry and every shop (see Figure 1).
A quality weld is a weld that fulfills the designer's intent. A problem in the production area can be historyâ€"a history of consistently perfect weld quality or a history of accepting welds that don't meet code, which can interfere with the welds currently made and cause problems about what is required. It is important that every weld meets the code or drawing requirements, doesn't exceed the weld size, or fall short of the required quality. However, when the decision is made always to provide only minimum-size welds that just meet the code, the weld may be rejected by other inspectors in subsequent manufacturing processes or when warranty issues arise.
Welder performance certification should be required before any welder begins work on production parts. From the first day of employment with the company, every welder must demonstrate proficiency and the ability to weld as required for the specific assignment. Properly managed and organized welding operations always utilize approved welding procedure specifications (WPS) to communicate to all persons associated with the welding operations what is expected for a product. The WPS contains procedural documentation concerning the design of the weld joint, the base material type and grade, the welding process, consumables and equipment, the essential variable ranges (volts, amps, travel speed), and the acceptance range of essential variables and weld quality the customer expects. All departments involved in welding need to have access to and understand the WPS and what is expected in the final welds, which are essential for success.
In a production welding setting, welders always should try to weld in the flat position. Designers know that fillet welds require the least joint preparation and cleanup. Welders also should avoid weld spatter, breathing the welding fumes and smoke, and grinding welds. They should try to remove the slag and minimize time required for cleanup (see Figure 2).
Helping Welders Achieve Quality Welds
In-plant visual samples can help welders remember the appearance acceptable and rejected welds have. A wall-mounted board keeps these reminders readily available for easy reference for all welders, quality control personnel, and managers. The welder must remember that, as the first inspector of every weld, the decision to accept or reject is made while the hood is down and the arc is on, since they are the only ones who can actually see the puddle of the root pass and catch a defect during the root weld pass, or while the puddle is still molten.
Published acceptance criteria in the codes are a minimum standard of acceptability. The welder should avoid the minimum acceptable weld, because when a weld falls beneath that minimum, rejects must be repaired.
Nondestructive testing tools allow for timely, in-process weld inspection. Aside from visual inspection criteria, welders can perform liquid penetrant inspection or magnetic particle tests of welds in-process and to finished welds before quality control checks. Welders who fail to perform personal inspections can drain a company's finances (see photo at top of page).
Accountability and responsibility from all members of the weld team improve weld quality. Every person involved in design, purchase, operations, and quality needs to leave their contact number with the welding supervisor to provide timely responses if welding difficulties occur. Also, welders should place their stencil number on every completed weld to properly identify who completed the job.
A welder must keep his mind on the welding and watch the puddle he is making. When the welder is thinking about personal problems, concentration is lacking and problems will arise. When a welder is anxious to get out the door at the end of the shift, it is easy to think about punching out at the time clock and forget about quality welding.
Welders and quality control welding inspectors face a continual push-pull between the production of welded products. It is important always to remember that they are both on the same team and strive for efficiency, quality, and customer satisfaction.
Finally, welders must be honest with management and with themselves. If new tools are needed, they should get them. If vision is a problem, they need to get glasses or portable lights. If the weld is inaccessible, they can stop and change the design or create a subassembly. No one can inspect quality into a welded part.
Quality is a relative term and means compliance with the code and the designer's intent.
Tips to ensure weld quality
· Understand the latest revision of the print and welding symbols.
· Know the code, specification, essential variables, and acceptance criteria.
· Know when to perform welding inspections or stop fabrication for quality control inspection.
· Always keep the workplace safe, ventilated, well-lighted, and clean.
· Wear gloves and protective clothing.
· Make sure the helmet hood and lenses are in good repair.
· Wear clean, neat clothes and safety boots. Dress like a professional welder.
· Monitor the equipment condition and operation, and have extra tips, cups, and liners on hand.
· Wear prescription, safety glasses, or magnifying hood lenses while welding.
· Keep hand tools (pliers, screwdrivers, and wire cutters) readily available.
· Keep enough consumables, gas, inerts, and backings readily accessible and safely stored.
· Know common weld joint designsâ€"weld surface requirements, root openings,
· bevel grooves, including the correct angles, backing, or backgouging.
· Maintain parts at the workstation and be supplied by assigned material handlers.
· Monitor the essential variables in the WPS, such as amps, volts, and travel speed.
· Weld in the flat position or use a turntable.
· Know preheat and postweld heat-treatment requirements and use a temp stick.
· Use the preferred technique for product consistency.
· Know the welding code requirements and scheduled nondestructive testing.
· Have a set of fillet weld gauges, a measuring tape, metal ruler, and mechanical devices to measure for correct root openings and weld sizes.
· Realize that every time anything is done to a part, it costs the company money.
Friday, December 26, 2008
First line of defense-Educating welders to achieve quality welds
Posted by BR at 10:02 AM
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