Question 7 of 7: Case Study — Spray-Gun Clogging Incident Resulting in Amputation

Question 7: Case Study — Spray-Gun Clogging Incident Resulting in Amputation (20 marks: 6/6/8)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

(a) Determining the Cause of the Accident

Applying the unsafe-act/unsafe-condition framework and root-cause analysis from Questions 1 and 2, the accident has an immediate cause and several underlying (root) causes:

• Immediate/direct cause: the employee attempted to clear the clogged nozzle tip with the spray gun's trigger mechanism still capable of actuating and the delivery line still pressurized — an unsafe act performed under the reasonable but mistaken assumption that a "failed to operate" gun was in a safe (de-energized) state.
• Contributing unsafe condition — no de-pressurization/lockout procedure for clog clearing: the equipment and/or written procedure did not require the employee to shut off the supply, bleed residual pressure, and (where fitted) engage a trigger safety lock before attempting to clear the tip — a task-specific lockout for a low-pressure spray system that was apparently not established or not followed.
• Contributing unsafe condition — inadequate job safety analysis: "clog clearing" is a foreseeable step in this job (the narrative states the gun clogged after "several gears," implying it is a recurring event with this rust-preventative/gun combination), yet no JSA appears to have identified it as a distinct hazardous sub-task requiring its own safe procedure, separate from normal spraying.
• Contributing unsafe condition — inadequate training: the employee was not trained (or the training was insufficient) on the specific hazard of a pressurized/energized gun and the correct de-energizing procedure before attempting field maintenance on it themselves.
• Contributing management-system cause: equipment maintenance (clearing a recurrently clogging tip) was left to the production operator rather than being a scheduled/authorized maintenance task with its own controls.

The determined cause is therefore not simply "employee carelessness": it is an unsafe act (attempting to clear a live spray gun by hand) made possible by unsafe conditions (no required de-pressurization step, no JSA covering clog-clearing, and insufficient training).

(b) Corrective Actions Required

1. Engineering control — install/verify a trigger-lock or lockable shut-off valve on the spray gun and supply line so the gun cannot discharge while being cleared or serviced, and require it be engaged before any manual work on the tip.
2. Engineering control — provide a dedicated, safe unclogging method — e.g. a spare pre-cleaned gun swapped in immediately, or a soak/solvent-bath clearing station away from the operating position, removing the incentive to clear a live gun at the workstation under production pressure.
3. Administrative control — write and implement a lockout/de-pressurization procedure specific to this task ("shut off supply → trigger to relieve residual pressure → engage lock/tag → then clear tip"), incorporated into a formal JSA for the spray-packaging job that explicitly covers the clog-clearing sub-task, not just normal spraying.
4. Training — retrain all employees performing this job on the hazard, the new procedure, and why bypassing it is dangerous even when it "only takes a second," reinforced with hands-on demonstration and competency verification.
5. Reduce the underlying clogging frequency — investigate why the gun clogs recurrently (wrong nozzle size/type for the rust preventative's viscosity, inadequate filtration, product left to partially cure in the tip between uses) and correct it, which reduces how often the hazardous clearing task must be performed at all — an application of the elimination/substitution end of the hierarchy of controls (Question 6(ii)) rather than only adding controls around the existing failure-prone equipment.
6. PPE review — confirm appropriate hand protection is specified for this task, while recognizing (per Question 6(iii)) that PPE would not have prevented this specific injury mechanism and must not be treated as the primary corrective measure.

(c) Follow-Up Action Required

• Regulatory incident reporting — report the amputation to the applicable provincial OHS regulator within the mandated timeframe (a critical/lost-time injury of this severity is reportable), and to the Workers' Compensation Board, per the requirements of the applicable OHS Act.
• Formal incident investigation and documentation — complete a documented investigation using the root-cause analysis approach from part (a), retained on file and used as the basis for the corrective actions in part (b).
• Extend the JSA and corrective actions to every similar task/location — any other spray gun, gun/product combination, or work station with the same clog-clearing exposure across the plant, not just the one workstation involved, since the underlying unsafe condition is a task type, not a single piece of equipment.
• Verify and audit implementation — confirm the trigger lock/shut-off is actually installed and used, the revised JSA is trained on and followed, and schedule a follow-up inspection/audit (e.g. at 30/90 days) to confirm the corrective actions have not quietly lapsed once production pressure resumes.
• Review through the joint health and safety committee — present findings and corrective actions to the workplace health and safety committee, both to close the loop with worker representatives and to capture any additional insight from workers doing the job daily.
• Update the injured worker's return-to-work and accommodation plan, coordinated with the compensation board, reflecting the permanent partial disability from the amputation.
• Feed the incident into the training program as a case example for future spray-equipment and lockout/tagout training, closing the loop from a real event back into prevention.