Making structural repairs in the field
Tips for solving typical problems
Planning, gas, rigs, tips, location, and cutting all have significant effects on field welding jobs. Taking these into account may save you a lot of time and trouble when doing repair on structural members.
Any structural welder will tell you that it's a nuisance to fix someone else's repair work error, but mistakes happen--at the drawing board, in the fabrication shop, and in the field.
This becomes an even more significant challenge for several reasons when the repair must be completed in the field. First, all of the desired tools may not be as readily available as they would be in the shop. Second, when problems are discovered in the field, less schedule flexibility exists compared to in the shop, so operators might be rushed to accomplish the fix, thereby increasing the risk of cutting corners and not performing the best-quality repair.
Repairs may be necessary to correct an apprentice's innocent mistake, or a journeyman's inexcusably shoddy work. Additionally, what may have appeared to be a good idea to a designer in an office might not work 30 floors above the ground, where actual field conditions can affect the outcome dramatically.
Repair work is needed for many different reasons. Plans may be drawn or interpreted incorrectly, stiffener plates may be welded at the wrong dimensions, braces may be in the wrong place or even upside down, or columns and beams may need to be adjusted. General contractors want the problem corrected as soon as possible. They don't want to hear excuses or explanations—they want it fixed. In the field, time is money. That is the bottom line.
General contractors expect the structural welder to repair the problem, and many times this presents the welder with a difficult scenario. Many situations are beyond the control of the field welder: He has no choice about which cutting gas to use, and often the cutting equipment is not in the best condition, usually having dirty tips. Also, the welder may have to use a different setup every day, and it's up to him to get the cutting rig to the location of the repair work. Contractors don't want to hear about these details. They just want the repair done so the project can proceed.
Another nightmare for the welder is when someone else does the cutting. A person who doesn't have to do the welding may not worry much about the fit-up job afterward. An unqualified worker often butchers the plate or structural member to get the wrongly fabricated section off.
Even skilled workers can rush the job, resulting in shoddy cutting techniques. These poor-quality welds can result in extra payroll for welding time, distortion because of the extra heat used for filling unnecessary gaps, and wasted electrodes.
So what isthe best course of action when a welder makes field repairs? The following are some solutions to these problems.
Probably the most common cause of an unsuccessful or excessively costly repair is lack of planning. Time spent carefully planning the entire repair operation easily will pay for itself when the repair is accomplished with no unexpected problems that reduce quality or increase the amount of time required to perform the repair.
If the mistake is due to bad prints, the contractor tells the general foreman what needs to be fixed. The general foreman tells the foreman, and the foreman tells the welder what needs to be done. Many times, a foreman, an engineer, or a general contractor will provide the welder with a repair sketch and instructions. A welder always should keep the sketch, even after the repair is complete, as proof in the event that the repair turns out to be unacceptable.
Most structural cutting done in the past was with acetylene, the hottest-burning flammable gas. However, many cutting jobs are done with MAPP® because of its cleaner burning properties. MAPP is similar to acetylene, but it doesn't burn as hot, and a welder who is used to working with oxyacetylene cutting equipment will have to familiarize himself with its use. In fact, the welder needs to be familiar with all the different fuel gases that may be used in the field.
Oxyfuel Cutting Equipment
In field repair, the welder uses many different cutting rigs, which comprise an oxygen cylinder, an acetylene cylinder, a regulator, and a torch assembly. In the field, this equipment usually is on a cart with either solid rubber or pneumatic tires for portability. They usually have a lifting eye so they can be lifted with a crane; however, such lifting attachments should be checked routinely to ensure a safe connection point. Ideally, specially designed cylinder holders should be used when the cutting equipment must be lifted to the work position. In either case, the welder should make certain the regulators are removed from the cylinders and the protective caps are attached securely before movement. Each subcontractor should have a few different rigs, depending on how many crews he has. The subcontractor should make sure all equipment is in working order, but sometimes subcontractors or workers don't maintain the equipment, leaving dirty, fouled tips.
The welder does have some control over this situation, however. All it takes is a set of tip cleaners. Everyone who cuts should have tip cleaners, cutting goggles, and a striker as standard tools. A clean tip equals a clean cut, resulting in a good fit-up.
Getting to the location of a repair usually is more of a problem on a large job. The welder may need an elevator or crane just to get the rig to the repair location. This requires ingenuity and, many times, good people skills.
Cooperation among subcontractors at a site usually pays off for all parties. One company that allows another company to use its crane to place a cutting rig not only promotes good will, but also may result in a repaid favor. It also is important for field welders to become familiar with their co-workers and not be afraid to ask for help.
Repair Work With Confidence
More than one-quarter of all welders belong to unions.1Journeymen ironworkers typically do field welding, and most belong to the International Association of Bridge, Structural, Ornamental, and Reinforcing Iron Workers union. These unions give them the opportunity to upgrade their skills by taking journeyman upgrade classes and practicing in apprentice shops.
Just about anything can be repaired with a good torch, welding machine, and grinder. A confident welder will tackle and solve field problems. Confidence comes from knowledge, skill, and a good attitude. It's important to identify the problem, come up with a solution, and go for it.
1. America's Top 300 Jobs, 6th ed. (JIST Works, Inc., ©1998).
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