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Cutting and Welding Fires: How to Prevent Them

Fires rarely occur where permanent cutting and welding production equipment is installed, as adequate safeguards are commonly part of the installation. However, the danger of fire is greatest when cutting or welding is performed during:

  • · Building maintenance
  • · Machinery repair
  • · Other nonproduction activity

This is especially true when an outside contractor is asked to do the job, because the contractor may not be familiar with plant operations and hazards that may exist.

It has been estimated that approximately 6% of all industrial fires start where portable cutting and welding equipment was used without adequate safeguards. Neglecting to take necessary safeguards can result in serious fires. Cutting and welding operations are performed more safely when proper precautions are taken.

How Fires Start

Knowing how cutting and welding fires occur is important in learning how to prevent them. Heat that can start a fire can come from:

  • Contact with the oxyacetylene flame
  • Heat transmitted from the metal being cut or welded
  • Molten slag that is produced from the cut
  • Sparks which fly from the work

Some materials will catch fire from these sources of heat more quickly than others. Flammable gases and liquids are examples of substances that can be easily ignited. Oily rags and combustible materials such as burlap, cardboard, straw and wastepaper catch fire easily and burn vigorously, once started.

Wooden flooring, scrap lumber, tarpaulins and similar materials will not catch fire as quickly as those mentioned above. However, special precautions are also necessary around these materials, as they may only smolder at first, then flare up at a later time.

Watch Out for Sparks

Sparks may lodge in cracks in woodwork or drop through holes or other openings onto combustible materials within the walls or on floors below. Fires have occurred when sparks and molten metal from cutting operations fell through air ducts and ignited air filters.

Many people do not fully comprehend how far sparks can travel or how easily they get into unseen corners or cracks. Sometimes sparks can be thrown for distances up to 30 or 40 feet. Particles of iron or steel may retain enough heat to start a fire up to 15 seconds, or even longer under some conditions.

Basic Precautions for Fire Prevention

Move Objects to Safe Location

When possible, move the object to be cut or welded to a fire-safe location, such as a noncombustible or fire-resistive room or a building essentially free of flammable and combustible contents.

Move Combustibles Away from object

If the object to be cut or welded cannot be moved, all combustible material should be moved at least 35 feet away.

Cover Immovable Combustibles

If the surrounding combustible materials cannot be moved, then they should be protected with flame-resistant covers or shielded with fire-resistant guards.

Use a Fire Watch

A fire watch with a proper fire extinguisher should stand by while cutting or welding is taking place. Where there is a possibility that sparks may fall to floors below, additional fire watchers may be needed.

If these basic precautions cannot be taken, then welding or cutting should not proceed. If basic precautions can be followed, the designated, responsible person should confirm that the following steps have been taken to ensure that the cutting or welding operation is performed safely.

  • Ensure that all welding equipment has been thoroughly checked to ensure it is in proper working order.
  • Confirm that the welding operator is competent to perform the task to be completed.
  • Take extra precautions when cutting or welding is performed on an automatic fire sprinkler system or in areas where the sprinkler system is shut off.
  • When cutting and welding near painting operations, areas where flammable gas is stored or used, or in rooms containing loose, readily combustible material, make sure there is no possibility of sparks entering those areas.
  • Extreme care should be taken when repairs must be made in areas that contain or have contained flammable liquids, gases or combustible dusts. Ventilate the area thoroughly and remove all combustible materials. If cutting or welding is necessary on spray booths, booth ducts or on any other equipment where combustible residue is present, the residue must be thoroughly cleaned from the equipment before repairs are made.
  • Floors should be swept clean and combustible floors wet down or covered with wet sand before starting work. Cutting and welding should not be undertaken if the work is close enough to combustible walls, partitions or roofs to cause ignition by conduction.
  • A trained fire watcher should be stationed to extinguish any fires that may start. A trained fire watcher should also be stationed on floors above or below. Watch should be kept for at least 30 minutes after completion of the work to make sure that smoldering fires do not flare up.

Maintenance and Use of Equipment

While manufacturers of cutting and welding equipment have built-in safeguards to promote the safe and effective use of their equipment, not all accidents and damage can be controlled entirely. Protecting against cutting and welding hazards can only be accomplished by:

  • Purchasing safe equipment
  • Maintaining the equipment in a safe operating condition
  • Observing safe practices in the handling and use of the equipment

Make sure to follow these tips and precautions to help avoid any cutting and welding fires at your work sites.

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