Safe practices must be the first consideration before starting any welding, cutting, brazing, soldering, bonding, or other shop opera1 ion. A specific reference is the American national standard, ANSUASC 249.1, Safety in Welding, Cutting and Allied Processes, latest edition, published by the American Welding Society, Miami, Florida.

The main causes of fire accidents in welding are improper maintenance, and incorrect handling and use of the equipment. Some examples are:

Oxyacetylene Flame. Serious fires can be caused if the flame comes in contact with combustible materials in the immediate vicinity of the work.

Electrode Holder. A fire can be started if the holder is handled so that it comes in contact with conducting material or with combustible material.

Hot Metal. Small pieces of metal that drop from the work are dangerous. Glowing bits of iron or steel stay hot enough to start fires for 15 to 20 seconds. Even pieces at black heat in daylight may ignite combustibles on which they fall.

Molten Slag. Molten slag that drips from the work is very hot and extremely hazardous. Even after falling a considerable distance, for example, down a long elevator shaft, it may retain enough heat to start fires.

Sparks. The “sparks” that fly from the work actually consist of small globules of molten metal, which are thrown out in heavy showers, especially in cutting operations, for distances as great as 9 m (30 feet). They are usually hot enough to ignite combustible

materials on contact, and as they bounce and roll along floors, they can start unobserved smoldering fires that later can burst into flames.

Safeguards

Production. Welding and flame cutting operators should be provided with protective clothing, suitable to the kind of work to be done. Where welding and cutting are part of the regular production processes, the work area should be kept clear of combustible

materials at all times. This precaution should be rigidly enforced, since the presence of anything that will burn constitutes a fire hazard.

Special Work with Portable Equipment. Dangerous conditions are predictable when portable welding or cutting equipment is used in areas containing combustible materials. Almost all fires due to these processes start in areas not normally used for welding or cutting operations that have not been checked for fire safety.

The best practice is to move special welding and cutting jobs to locations where the work can be done with assured safety. When this is impossible, the following routine is mandatory:

Preliminary Survey. The person in charge of the welding or cutting work should carefully examine the site of the proposed job with a qualified person who has local authority, noting all hazardous conditions. Among the factors to be noted are the following:

(1) Wooden floors

(2) Moveable and immovable combustible materials near the work site

(3) Flammable liquids in containers, flammable vapors in the air, and combustible dust in the neighborhood.

(4)The possibility of sparks reaching combustible materials in adjoining spaces through cracks or holes in floors, walls, open or broken windows, and open doorways.

(5)The possibility of fire being started by hot metal or slag dropping from a height. Work should be undertaken only if it is decided that all hazards can be removed or thoroughly protected. It is impossible to over-emphasize this point: death and widespread destruction can be the result of taking chances.


Before Starting.
Remove all combustibles away from the work, at least 8 m (25 ft) when welding, and 11to 12 m (35 to 40 ft) when cutting. If there are combustibles within these distances that cannot be removed, confine the sparks by surrounding the work with metal shields, fire-proof curtains, or other suitable guards, making sure that sparks cannot fly through any openings or roll out under the guards.

Use -fire-resistant coverings to protect objects in the area that are likely to ignite.

When a wooden floor must be protected from burning, or a concrete floor from spalling, place a container of water or a pan of sand immediately under the work to catch slag.

Before starting to cut off a piece of metal, make sure it will not drop where it can start a fire. To prevent the piece from falling, a rod or bar can be welded tothe piece and held by a helper while the cut is made.

Check to assure that adequate portable fire extinguishing equipment has been provided. If the area has a sprinkling system, get assurance from the proper authority that the sprinklers are ready for operation. Sprinklers should never be shut down while welding is in progress. Sweep the floor clean, and if it is made of wood, wet it down.

A written permit form should be obtained from the proper authority to perform cutting operations outside the usual maintenance shop.

Portable Fire Extinguishers

The fire extinguishers available must be appropriate to the hazards present. Where wood or other ordinary combustible materials may be ignited, extinguishers approved for use on Class A fires are required. If flammable liquids or electrical apparatus may be involved, extinguishers approved for use on Class B or Class C fires must also be provided. The types of extinguishers approved for use on different classes of fire are shown in Table F-1.

 

Where any danger of setting fire to combustible materials exists, it is important to station a person with appropriate hand-held extinguishers who will stand by the work throughout its progress, no matter what other precautions have been taken. An extra person is needed for fire extinguishing duty because the cutting or welding operator, wearing dark glasses or a hood, cannot see small fires if they are started.

The watcher should remain at the scene of the work for at least 30 minutes after the work is completed. The watcher should be required to look carefully for smoke or fire before leaving. This is especially important if welding or cutting sparks may have started smoldering fires in wooden structures or in other slow burning materials.

Reference: National Fire Protection Association.

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