OHS Code Explanation Guide

Published Date: July 01, 2009
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Part 10 Fire and Explosion Hazards

Section 171.1 Welding – General

Subsection 171.1(1)

The employer must ensure that welding activities comply with CSA Standard W117.2-06, Safety in Welding, Cutting and Allied Processes. The Standard provides minimum requirements and recommendations to protect persons who work in an environment affected by welding, cutting, and allied processes. It is also intended to prevent damage to property arising from the installation, operation and maintenance of equipment used in such processes. The Standard identifies the requirements for the operation of cutting and welding equipment, and equipment of related processes. In doing so, the Standard addresses specifically the operator of such equipment, the supervisor, and the employer under whose authority such operations are carried out. The Standard identifies the health and safety hazards that may be encountered when such equipment is operated. It provides two options to the employer on how to implement the necessary health and safety measures by

(a) following procedural guidelines identified in the Standard, or
(b) implementing a health and safety program.

When welding on a boiler, pressure vessel or pressure piping system, the requirements of the Pressure Welder’s Regulation (AR 169/2002) are also applicable.

Subsection 171.1(2)

No explanation required.

Subsection 171.1(3)

Employers must ensure that before welding starts, an inspection of a reasonable area surrounding the welding operation is carried out and that combustible, flammable and explosive material, dust, gases, or vapours that are present or likely to be present in the work location are identified. Steps must be taken to ensure that such materials are not exposed to ignition by taking one or more of the following actions:

(a) have the combustible, flammable and explosive material, dust, gas, or vapour, or the sources of these, moved a safe distance from the work location;
(b) have the combustible, flammable and explosive material, dust, gas or vapour properly shielded against ignition;
(c) have the work moved to a location free from combustible, flammable and explosive material, dust, gas, or vapour;
(d) schedule the welding operation so that such combustible, flammable and explosive material, dust, gas, or vapour is not exposed during welding and cutting operations;
(e) other effective methods that will render the area safe.

For more information
ANSI/NFPA Standard 51B, Standard for Fire Prevention in Use of Cutting and Welding Processes.
American Petroleum Institute, Recommended Practice 2201, Procedure for Welding or Hot Tapping on Equipment in Service.
Alberta Boiler Safety Association, AB-513, Alberta Repair and Alteration Requirements.

Subsection 171.1(4)

In addition to barrier protection from such hazards as falling tools or materials, other people in the work area should also be protected from the intense light of the welding arc, heat, and hot spatter.

Subsection 171.1(5)

When not in use, electrodes must be removed from holders to eliminate danger of electrical contact with persons or conducting objects. When not in use, electrode holders should be placed so that they cannot make electrical contact with persons, conducting objects such as metal or wet earth, flammable liquids, or compressed gas cylinders. When not in use, guns of semiautomatic welding machines should be placed so that the gun switch cannot be operated accidentally.

Subsection 171.1(6)

The work lead and the ground lead are not the same. The work lead should not be referred to as the grounding lead. It is preferable to connect the work lead directly to the work. The work clamp should never be stored by clamping it to any part of the grounded power source frame. Grounding of electrical systems and circuit conductors is done to limit voltages due to lightning, line voltage surges, or unintentional contact with higher voltage lines, and to stabilize voltage to ground during normal operations. Grounding of workpieces, equipment housings, metal cabinets and frames, or other conductive material that form part of the equipment is done to limit the voltage to ground on these items. Limiting the voltage by grounding helps to prevent accidental shocks when equipment is misconnected or insulation fails.

After assembling any connection to the machine, each assembled connection should be checked before starting operations to ensure that it is properly made. In addition, the work lead should be firmly attached to the work. Clean and tight connections are necessary to prevent local heating. Properly insulated and dry connections are necessary to prevent stray electrical currents and possible shock or short circuits.

Coiled welding cable should be kept to a minimum and any excess is to be spread out before use to avoid overheating and damage to insulation. Jobs alternately requiring long and short cables should be equipped with insulated connectors so that idle lengths can be disconnected when not needed.