Cracked Disc, Thinner Can and Torch in the Same Bay
A two-bay repair shop has one 230 mm angle grinder and one 100 mm grinder. A trainee is smoothing body filler on a vehicle door while a mechanic uses an oxy-acetylene torch four metres away to heat a seized bolt. The roll-up door is open one metre; an extractor fan trips the breaker; there are no welding screens. The trainee wears safety glasses, cotton overalls and open sandals. The 230 mm grinder has a disc with a visible crack and the guard is removed because it fouled the door aperture. A 20 litre plastic jerrycan of thinner sits on the floor within three metres. The supervisor is off-site. The trainee asks whether to finish the door before lunch because the customer is waiting. The shop has a face shield, leather gloves, a welding screen, and a proper flammable store, but they are in a locked cabinet. The trainee has not used a 230 mm grinder before.
1. What immediate stop-work actions would you take, in order, and which hazards make each action urgent?
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The first priority is to stop both ignition sources, not to finish the job. I would signal the mechanic to shut off the torch and close the cylinder valves, then switch off and unplug the grinder. Next, move the 20 litre thinner can to the flammable store and open the roll-up door fully; the cracked disc and missing guard make the grinder a fragmentation risk, while the thinner vapour plus oxy-acetylene torch create a fire and explosion risk. I would lock off or tag the faulty extractor circuit because a fan that trips the breaker may be electrically unsafe. The trainee must not use the 230 mm grinder: no training, open sandals, no face shield. I would clear the area, put up a barrier, and call the supervisor. Work resumes only after the disc is replaced with one rated for the grinder speed, the guard is refitted, the area is ventilated, the torch is screened or moved, and PPE is worn. Grinding near a locked cabinet is not acceptable until the cabinet is secured and the area made clear.
2. Using the hierarchy of control, what permanent changes should the supervisor make before any grinding on a vehicle is allowed?
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Use the hierarchy in order. Elimination: do not grind filler while a torch is being used; move the heating job to a separate bay or time. Substitution: use the 100 mm grinder with a correct disc for confined door work, or hand-sand where practical. Engineering: refit the guard, fit a dust extraction hood, repair the extractor circuit, install welding screens and a spark blanket, and store flammables in a closed metal cabinet away from the work. Administrative: a written hot-work permit, a 10 m clearance zone, fire watch, training and supervision for the trainee, and a check that the disc speed rating is at least the grinder no-load speed. PPE: face shield over impact goggles, hearing protection, dust mask, leather gloves, close-fitting overalls and safety footwear. PPE is last because it does not stop a burst disc or vapour ignition. The supervisor should also record the defective guard and extractor and remove them from service until repaired.
3. If the door must be ground today, write the safe set-up you would require.
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Only a trained operator should use the grinder. Move the vehicle or the torch so there is at least 10 m clear, or screen the torch with a fire blanket; remove all thinner, paint and solvent containers from the bay. Fit a correct 230 mm disc, inspect it for cracks and ring-test it, refit the guard, and check the no-load speed. Use the 100 mm grinder if the guard cannot be fitted to the 230 mm tool. Secure the door on a stand, connect dust extraction, and position a CO2 extinguisher and fire watch. The operator needs a face shield over goggles, hearing protection, a P2/P3 dust mask, leather gloves, overalls and safety shoes. Test the extractor before starting. Keep the cable clear of the work, use an RCD, and stop immediately if the disc vibrates or the extractor fails.