October 11, 2001
Proper clothing, training, procedures, troubleshooting, preparation, and equipment for HF welding are critical if you want to prevent workplace accidents.
In an era of corporate downsizing and intense competition, companies are under mounting pressure to keep operating costs to a minimum while improving productivity. Every program is being scrutinized to justify its continuation in this tough economic climate.
However, companies should not back cut in the area of personnel safety. By strengthening and maintaining safety programs, companies not only protect their employees but also add to the bottom line. Unsafe industrial practices can lead to wasteful downtime, not to mention the potential loss of valuable personnel. Upholding the highest safety standards, therefore, makes good economic sense—common sense.
This article focuses on ensuring safety while performing high-frequency (HF) welding on a tube mill. HF welding safety must be a comprehensive effort. It runs the gamut from the relatively sophisticated task of performing welder fault diagnostics to the type of shoes an operator wears. Every aspect in a welding safety program is important and should be treated seriously.
To ensure proper safety practices, mill operators and maintenance personnel should be aware of six significant issues:
3. Procedural maintenance
4. Assistance in troubleshooting
5. Preparation and operation
When you ride a motorcycle, you wear a helmet. When you drive a car, you wear a seat belt. What is the proper protective gear for operating an HF welder? The five common-sense items are safety glasses, a hard hat, a conventional work uniform or coveralls, work boots, and work gloves.
On the other hand, clothing to be avoided includes sneakers or regular shoes, loose-fitting shirts, ties, shorts, chains and jewelry, and baseball caps. Such items can snag on equipment or not offer sufficient protection from machinery accidents.
To operate high-powered machines such as HF welders safely, operators must receive thorough training from experienced in-house personnel or manufacturers' representatives. Common sense says that HF welding is not a skill a person wants to learn by trial and error.
Welding operators and maintenance workers should be familiar with those issues pertinent to their responsibilities, such as the basics of HF welding, fault diagnostics, equipment features, lockout and tagout procedures, preventive maintenance, and troubleshooting options.
The main ingredient of any maintenance program is a documented, Occupational Safety and Health Administration (OSHA)-approved lockout/tagout procedure.
Locking out and tagging out the power source feeding the HF welder means that no available voltage will be present on the line side of the welder's main circuit breaker. It only makes sense that the complete welding system must be disconnected from the power source during maintenance.
Questions about the lockout/tagout procedure can be answered by calling the local OSHA office.
A solid background in electrical or electronic operations and a thorough understanding of how the welding system works are two requirements for safely performing equipment troubleshooting. If a maintenance worker lacks these capabilities, he or she should immediately contact the welder manufacturer for guidance.
Another good, common-sense safety practice when troubleshooting is to use the "buddy system." Welders should never troubleshoot alone but instead should enlist the help of a trained co-worker. Two sets of hands, eyes, and brains are better than one.Preparation and OperationBefore operating an HF welder, personnel should perform these basic preparations:
1. All panel covers and doors must be properly fastened and completely closed.
2. Work areas should be free of items that might interfere with a person's movement.
3. All walkways should be dry and free of oil or mill coolant.
4. All necessary inspections, without exception, should be carried out before turning on the welder.
Once the welder is up and running, operators must never:
1. Adjust or touch the work coil or contacts.
2. Adjust or touch the impeder.
3. Open doors or panels.
4. Get too close to the coil or contacts.
In other words, use common sense.
HF welding equipment consists of an oscillator or radio frequency (RF) generator, a direct current (DC) power supply, a distilled water heat exchanger, a weld head (for contact welding), a bus bar (for induction welding), and welder controls.
To ensure equipment safety:
1. Install all external interconnect wiring in accordance with the local electrical codes.
2. Install all external water piping using plastic or nonferrous materials.
3. Properly ground all equipment.
4. Mount and secure all cabinets to their platforms or mill bases.
HF welders should have built-in safety devices to protect operators and maintenance personnel. Doors and panels should be interlocked so that if they unexpectedly open during operation, the welder will shut down automatically. Gravity-grounding devices should be installed on the oscillator and DC power supply to discharge any capacitors to ground if a door opens. (Note that gravity-grounding devices are not needed for solid-state welders).
Each cabinet should have an externally mounted, hand-resettable emergency stop button that is accessible at all times. In fact, several of these e-stops should be installed along the mill line.
Plant personnel should never bypass or jumper-out door interlock switches, remove gravity-grounding devices, or bypass or jumper-out e-stop buttons. That kind of behavior goes against basic safety judgment.
To ensure safe HF welding, operators and maintenance personnel should be properly trained, keep their work areas clean at all times, never take safety short cuts, never override safety devices, always wear the proper clothing, never hesitate to ask for assistance, and, above all, use good common sense.