Setting Up a Weld So the Arc Is the Only Hazard

Purpose

To reduce the hazard list on a welding job to one entry before the arc is struck. The arc is a hazard with three routes of its own - ultraviolet and infrared radiation, the fume it generates from the consumable and the base metal, and the welding circuit's electrical shock - and those three deserve full attention. They do not get it on a job that also has combustibles under the work, a coating in the joint, a live machine below, leads across the walking line and a fall exposure at the working edge. Every route this procedure removes is one fewer thing competing for the welder's attention with the one route that cannot be removed.

Each step below produces a physical change plus a verification. A step whose output is only a signature has not been performed.

Scope

Applies to any arc welding, arc gouging or thermal cutting performed by shop personnel, in the shop or in the field. It covers setup only, and it hands three subjects off rather than restating them:

• Fire prevention, ignition control, the perimeter and the fire watch belong to the hot work permit and the hot work cards in this library, under 29 CFR 1910.252(a) in general industry or 29 CFR 1926.352 in construction.
• Fume constituents and which control each one needs belong to the welding fume card, under 29 CFR 1910.252(c) or 29 CFR 1926.353 and the specific substance standards.
• Equipment installation and maintenance requirements belong to 29 CFR 1910.254 for arc welding and cutting equipment, and 29 CFR 1926.351 in construction.

Roles and responsibilities

Procedure

1. Fix the scope and the process first. Which joints, which process, whether any cutting or gouging is involved, and where the work will physically be performed. This comes first because the process decides which routes exist at all: a job done with an arc process and no fuel gas has no cylinders at the workstation, and a job whose cutting is done at the bench does not carry the cutting hazards to the working level. Skipped: you build a control set for a job that is not the job.

2. Write the route list before you remove anything. Walk the workstation and name every way somebody can be hurt, by route rather than by hazard name: burn, inhalation, shock, fall, struck-by, ignition, stored energy. Writing it down first is what makes step 9 possible, because you cannot verify a list you never made. Skipped: you remove the obvious four and never notice the fifth.

3. Clean the joint before the arc, not around it. Coatings, paint, galvanizing, plating, oil, cutting fluid and heavy rust come off the joint and back from it, with the distance owned by the governing document or the coating manufacturer's guidance. The removal is its own inhalation exposure, so grinding or brushing a coating off is done with capture at the tool or with respiratory protection under a written program meeting 29 CFR 1910.134, never with a face shield alone. Never degrease with a chlorinated solvent anywhere its vapour can reach an arc, because the ultraviolet decomposes it into phosgene and other irritants. Skipped: the coating's metals go in the breathing zone, and the same contamination causes porosity.

4. Prove the workpiece itself is inert. A drum, tank, pipe or vessel that has held a flammable or its residue is not cut or welded until it has been cleaned or inerted, which is the requirement at 29 CFR 1910.252(a)(3). A pressurised line is isolated, drained and vented, and zero is confirmed at the piece being welded rather than at an upstream valve. Anything with stored mechanical or rotational energy, including a machine the work sits above, is shut down and locked and tagged at its energy isolating device under 29 CFR 1910.147; where the work is on electrical conductors or equipment instead, the standard is 29 CFR 1910.333(b)(2). Skipped: this is the step whose failure mode is an explosion rather than an injury.

5. Hand fire prevention to the permit. Establish the perimeter, including below and behind, and hand it to the permit authorising individual and the fire watch. Do not restate their job in your setup; do confirm the permit exists and that its end time covers the work plus the watch period. Skipped: the shop is running hot work on an assumption.

6. Position capture and ventilation before the first arc, not after the first plume. Capture velocity falls off steeply with distance, so a hood or an extraction nozzle is set close to the joint and re-set every time the work moves. Confirm the plume actually goes into it, by watching the first few seconds rather than by trusting the placement. Where the work is in a confined space, 29 CFR 1910.252(c) requires local exhaust or airline respirators and 29 CFR 1910.146 governs entry. Never ventilate any space with oxygen. Skipped: the control exists and does nothing, which is worse than no control because it is credited.

7. Inspect the circuit and establish the return. Check leads for damaged insulation, check the electrode holder for cracked or missing insulation, and clamp the work lead directly to the member being welded rather than relying on the structure, a chain, a hoist rope or a cylinder to carry the current. Keep the welder insulated from the work and from ground, keep gloves dry, and do not weld standing in water. Change electrodes with dry gloves. Skipped: the welding circuit's open-circuit voltage becomes the route nobody planned for, and current returning through a bearing or a rigging component damages what it passes through.

8. Screen the arc and brief line of sight. Ultraviolet burns corneas and skin well past the welder's own station. Screen the arc, and give anyone with line of sight either the minimum protective shade from OSHA's filter-lens table at 29 CFR 1910.133(a)(5) or a position outside the screens. Screens are finished so they do not reflect the arc, which 29 CFR 1910.252(b)(2) addresses along with protection of personnel. Skipped: the injury lands on somebody who was not doing the work and did not know they were exposed.

9. Re-walk the list and write down what is left. Compare the closed list against the list from step 2. Sort each entry into removed at source, controlled because it cannot be removed, or remaining. Anything in the middle column gets its control named beside it, because a route that is controlled rather than eliminated depends on a control staying in place for the whole job. Skipped: you believe the arc is the only hazard, which is the belief this procedure exists to test rather than to produce.

Worked case: a platform patch above a packaged rooftop unit

A steel access platform above a packaged rooftop unit needs a painted section of deck plate patched. Arc process, patch pieces cut to size at the bench. Step 2 produced eight entries.

Removed at source, five of eight.

1. Coating fume from the deck paint. Ground back from the joint before the arc, with capture at the grinder. Route gone: no coating in the arc.
2. Loose combustibles inside the perimeter. Cleared, and the perimeter handed to the permit.
3. Leads across the walking line. Rerouted along the platform edge and secured. Route gone rather than warned about.
4. Fuel gas cylinders at the working level. None went up, because cutting was done at the bench in step 1. This entry was closed by the process decision, not by a control.
5. The unit below, running and energized. Shut down and locked and tagged at its disconnect under 29 CFR 1910.147, so nobody is at it and nothing is running under falling slag.

Controlled because the route cannot be removed, two of eight.

1. The roof membrane under the platform. It cannot be moved. Controlled with a listed welding pad and blanket under the work plus the fire watch and the post-work watch period the hot work permit sets. This control has to survive the whole job, so it gets checked when the work moves.
2. The fall exposure where the patch reaches outside the platform guardrail. Controlled with a personal fall arrest system on an anchorage rated for it, under 29 CFR 1926 Subpart M on a construction site or 29 CFR 1910 Subpart D in general industry.

Remaining, one of eight.

1. The arc, with its three routes: radiation, controlled by screens plus the filter shade for the process and current from 29 CFR 1910.133(a)(5); fume from the consumable and the base metal, controlled by capture at the arc under the fume card's constituent assignment; and the welding circuit, controlled by the lead, holder and return checks in step 7.

Five removed, two controlled, one remaining, and 5 plus 2 plus 1 is the 8 the opening list held. The two in the middle column are the ones to name at the toolbox talk, because they are the entries that fail quietly: a blanket that got dragged aside when the work moved, and a lanyard clipped to something convenient rather than to the anchorage. Neither shows up as a defect in the weld.

What would change the answer. Put the same patch in a mechanical room instead of on a roof and entry 6 disappears while a confined space assessment appears, which moves ventilation from step 6's routine capture to 29 CFR 1910.252(c)'s local exhaust or airline respirator requirement and puts entry under 29 CFR 1910.146. Put it on galvanized deck rather than painted deck and entry 1 stays but its constituent changes from paint decomposition products to zinc oxide, and if any of the hardware in the joint is plated with cadmium the correct answer is to remove the hardware rather than ventilate harder.

References

• 29 CFR 1910.252 (welding, cutting and brazing, general requirements, including 1910.252(a) hot work fire prevention, 1910.252(a)(3) containers, 1910.252(b)(2) protection of personnel, and 1910.252(c) ventilation) and 29 CFR 1926.352 and 1926.353 in construction
• 29 CFR 1910.254 (arc welding and cutting equipment) and 29 CFR 1926.351 in construction
• 29 CFR 1910.147 for stored mechanical and rotational energy, and 29 CFR 1910.333(b)(2) where the work is on electrical conductors or equipment
• 29 CFR 1910.133(a)(5) for filter shades, 29 CFR 1910.134 for respiratory protection, 29 CFR 1910.146 for permit-required confined spaces, 29 CFR 1926 Subpart M and 29 CFR 1910 Subpart D for fall protection
• ANSI/AWS Z49.1, safety in welding, cutting and allied processes, in the edition your employer's written program adopts or your contract invokes
• See related: What Welding Fume Actually Contains and What It Needs; Running a Hot Work Permit That Would Hold Up; What Hot Work Actually Requires Before It Starts