Working safely while welding cutting burning or grinding.
I read in the news lately where an apartment building had gone up in flames due to a fire started by contractors using a torch in the basement. Many people were put out of a place to live due to an error by a contractor using a torch to cut out part of a floor. Based on the story there was no fire watch and not even a fire extinguisher on hand during the hot work.
Like most safety procedures the ways of being safe with hot work are simple. First you realize that cutting, welding or burning metal is going to produce hot bits of metal going places that you may not intend for them to go. These hot bits of metal can catch stuff on fire.
So begin by removing everything that can burn from the area. Most permit systems recommend a 30 foot clear space.
Next, make sure that you have a working fire extinguisher and some one to operate it. Don’t depend on the one doing the cutting, burning or welding to be able to watch for a fire while concentrating on the work.
The both the hot worker and the fire watch need to be aware that hot bits of metal can fly, roll or bounce a long way from the work site. They need to pay particular attention to any cracks or gaps near the work site. Apparently that is what happened in the story referenced above; sparks got into the wall and ignited the insulation.
Another cause of fires that is easily overlooked is material on the other side of the wall from where the work is being preformed. I read about one case where combustible material stacked outside a tank was set on fire by welding inside the tank. Heat can also be transmitted by infrared radiation as well as conduction. So workers need to be aware of all their surroundings when conducting hot work.
There are some locations where hot work cannot be performed at all. For example, in areas near where flammable liquids are present and vapors may be present, hot work should be avoided. Often the fabricators will have to be creative to perform the work without the usual cutting, welding or burning. Parts may have to be bolted or clamped in place rather than traditional mounting methods.
Flammable and explosive dust is a hazard in some operations. Combustible dust can be very hazardous if ignited in a confined area. I remember the demonstration that is done at the Factory Mutual training center. They atomize a cup of flour in an enclosed cave and set it off with a spark. The impact of the explosion can be felt across the street several yards away. Paper and wood dust can easily collect on structures and be difficult to extinguish if ignited by hot work.
Again, most safe work practices are simple to put in place. But often workers may feel prompted to take short cuts in order to expedite a job. Supervisors need to pay particular attention to jobs that begin close to the end of a work shift or done my contractors working on a bid price. There may be incentive to rush the job. The part that is most easily overlooked at the end of a job is the waiting period after a fire watch.
Sparks may take a long time to incubate into a fire. A spark that has fallen into a crack or crevice may smolder for a long time before becoming large enough to visibly see. The fire watch needs to stay with the job continuously for at least 30 minutes after work has been completed. The job site should be periodically checked for the next four hours to make sure that no fires have been created.
I have found it is difficult to get contractors working on a bid price to comply with the four hour fire watch. It is best to assign this duty to a security guard or other trusted employee who is paid by the hour to be there.
Contractor safety often begins in the bidding process. Begin by choosing contractors with a good safety record and who understand the unique hazards of your facility. Make sure contractors understand the hazards that they will be working in before they bid. You do not want to be in a situation where their ability to make a profit depends on taking unsafe shortcuts.
When doing cost estimates for a job involving hot work, be sure that the budget includes man hours for a fire watch during and after the hot work. These may seem like unproductive costs to a contractor not familiar with safe work practices but are required for good work practice. Having a fire watch effectively doubles the man hours required for a job.
When using a torch, care must also be made with the compressed gas cylinders. Compressed gas cylinders have their own unique hazards. Cylinders must be moved carefully using appropriate procedures. If cylinders are to be lifted, they must be properly rigged to reduce the change of dropping and damaging a cylinder. Cylinders must be properly secured both while in storage and during use in hot work. An appropriate cylinder cart will suffice in most cases to properly support the cylinders and safely transport them to the job site.
Electric welders and grinders have hazards normally associated with electricity. Make sure that the machines are of compatible voltage and the wiring is in good repair and well insulated. Hot work can easily damage the insulation of welding and grinding equipment so it needs to be inspected frequently and properly protected during the hot work process.
When welding, grinding or burning on vehicles, there are special hazards that apply. Most vehicles will be powered by a flammable fuel. Make sure the fuel is completely contained and hot work is preformed away from fuel tanks and fuel lines. Welding fuel tanks is a specialty best left to those brave souls who specialize in such work.
When performing hot work on a vehicle it is not practical or even possible to remove all the combustible material such as wiring harnesses, carpets, undercoating and upholstery. Extreme care needs to be taken to make sure heat does not transfer through the car body to combustibles on the other side of where the work is being done. I have read stories of whole cars being lost to fires under the dash or burning carpets due to a simple welding repair igniting material on the other side of the work.
Note that wiring can be damaged due to hot work even if it does not catch fire. The heat from welding in a roll cage or patch panel can easily cause an electrical short by heating up the insulation of wires hidden inside the body panels.
Cutting welding and burning are a part of any fabrication process. Just follow a few basic safety steps to make sure that the work does not cause more damage than good.
Please share your hot work safety suggestions or stories below.
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