Process Flow Chart Design, Hazard/Control Identification at Each Step, and an Alternate Hazard-Reduced Flow Chart: 23-Ind-B10 Workplace Health and Safety, May 2018, Q7

Question 7: Process Flow Chart Design, Hazard/Control Identification at Each Step, and an Alternate Hazard-Reduced Flow Chart (20 marks: 7/7/6)

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.

Check: this question is open-ended ("any industrial process"). The worked example below is a representative sheet-metal stamping and coating line, chosen because it exercises a wide range of common hazard types (mechanical point-of-operation, flammable solvent, thermal, and ergonomic) across a realistic 7-step process — any correctly-analyzed industrial process of at least 6 steps satisfies the question.

(i) Original Process Flow Chart — Sheet-Metal Stamping and Coating Line (7 Steps)

Fig. 1 — Original 7-step sheet-metal stamping and coating process: coil unloading → stamping press → deburring/trimming → solvent degreasing → manual spray-paint booth → oven curing → packaging.

(ii) Hazards and Controls at Each Step

Step	Hazard(s)	Control(s) in Place
1. Coil unloading & staging	Crush/struck-by from a heavy coil during crane/forklift handling; pinch points at rigging.	Mechanical lifting aids with rated rigging; trained/certified riggers; exclusion zone signage under suspended loads; steel-toe boots and gloves.
2. Stamping press (die forming)	Point-of-operation crush/amputation — a hand or finger in the die during a cycle.	Fixed point-of-operation guards, light curtains, and two-hand controls; lockout/tagout (LOTO) for every die change or jam clearance.
3. Deburring / trimming	Laceration from sharp sheared edges and hand tools; flying metal chips (eye hazard).	Fixed guards over trim blades; cut-resistant gloves; safety glasses/face shield.
4. Solvent degreasing bath	Inhalation of solvent vapour; skin/eye contact; fire/explosion from flammable vapour accumulation.	Local exhaust ventilation (LEV) over the bath; explosion-proof electrical fittings; bonding/grounding of the tank; chemical-resistant gloves/apron.
5. Manual spray-paint booth	Inhalation of paint solvent/overspray; fire/explosion from flammable overspray; skin/eye contact.	Ventilated, explosion-proof spray booth with filtered exhaust; organic-vapour respirator; coveralls and eye protection; no ignition sources permitted nearby.
6. Oven curing / drying	Burns from hot surfaces; fire/explosion from residual solvent vapour flashing off during heat-up.	LEL (lower explosive limit) vapour sensor interlocked to the oven's heating element and a purge cycle before heat-up; guarding on hot surfaces; oven-door interlock.
7. Packaging & palletizing	Manual-handling/ergonomic strain from repetitive lifting; forklift–pedestrian interaction.	Mechanical lift assists/conveyors; defined maximum manual-lift weights and team-lift procedures; pedestrian walkways and hi-visibility vests near forklift travel paths.

(iii) Alternate Process Flow Chart Reducing the Number of Hazards

The alternate design applies the hierarchy of controls (Question 6(i)) at the process level — substituting or eliminating the two highest-hazard-count steps (the flammable-solvent degreasing bath and the solvent spray-paint booth) and automating the point-of-operation exposure at the press — rather than only adding further controls to the original 7-step process:

Fig. 2 — Alternate 6-step process: robotic-fed progressive die replaces the manual press/deburr pair, aqueous washing replaces solvent degreasing, and powder coating replaces solvent spray painting.

Step 2 (robotic-fed progressive die combining stamping and trimming) — substitutes robotic material feed for the operator's hand at the point of operation, eliminating (not just guarding against) the crush/amputation hazard of the original Step 2, and combining trimming into the same progressive die removes the separate manual deburring step (original Step 3) and its laceration/flying-chip hazard entirely.
Step 3 (aqueous parts washer, replacing the solvent degreasing bath) — a water-based detergent wash substitutes for the flammable organic solvent, eliminating the fire/explosion hazard of original Step 4 and greatly reducing (though not entirely removing) the inhalation/skin-contact hazard, since the wash chemistry is far less volatile and non-flammable.
Step 4 (electrostatic powder-coat application, replacing manual solvent spray painting) — powder coating uses no flammable solvent carrier, eliminating the fire/explosion and solvent-vapour-inhalation hazards of original Step 5; overspray powder is also electrostatically attracted to the part and largely reclaimed, further reducing airborne exposure.
Step 5 (powder-cure oven) — because no solvent vapour is carried into the oven, the LEL/vapour-flash hazard of original Step 6 is eliminated; only the residual burn/hot-surface hazard remains, controlled the same way as before.
Step 6 (mechanized packaging and palletizing) — adds an automated palletizer to the mechanical lift assists already used in original Step 7, further reducing the manual-handling/ergonomic hazard (the forklift–pedestrian interaction hazard remains and is controlled as before).

Net effect: the alternate process reduces the 7-step, 8-hazard-instance original to 6 steps carrying materially fewer and lower-severity hazards — two entire fire/explosion hazard sources (solvent bath, solvent spray booth) are eliminated by substitution rather than merely controlled, and the highest-severity mechanical hazard (the press point of operation) is eliminated by removing the human hand from the danger zone entirely, consistent with the hierarchy-of-controls principle (Question 6) that elimination/substitution at the design stage outperforms adding further engineering/administrative/PPE layers to an unchanged process.

Topic. Constructing a representative industrial process flow chart, mapping step-by-step hazards to their in-place controls, and redesigning the process itself (not just adding controls) to reduce the underlying hazard count.

Key relations. Hierarchy of controls applied at the process-design level (substitution/elimination of a whole process step outranks adding engineering/administrative controls to an unchanged step); source–path–receiver placement of the controls listed in the hazard/control table; net hazard-count reduction as the metric comparing the original and alternate flow charts.

Why this works. Part (i) supplies the concrete process the rest of the question analyzes; part (ii) applies the hazard-identification-plus-control methodology from Questions 2, 3, and 6 to each real step of that process; and part (iii) demonstrates, on the same process, that redesigning around the hierarchy of controls (substitution/elimination) reduces hazard exposure more fundamentally than layering additional controls onto the original design.

Common pitfall. Producing an "alternate" flow chart that merely adds a control (a bigger exhaust fan, an extra guard) to the same process steps, rather than genuinely eliminating or substituting a hazardous step — the question specifically asks for a process that reduces the number of hazards, which requires changing what the process does, not only how each existing hazard is controlled.

Source. CSA Z1002 (hierarchy of controls, hazard identification); CSA Z432 (machine safeguarding, point-of-operation guarding); Brauer, Safety and Health for Engineers, Ch. 3–4 (source–path–receiver control, flammable-vapour/process hazards).

Question 7 of 7: Process Flow Chart Design, Hazard/Control Identification at Each Step, and an Alternate Hazard-Reduced Flow Chart

Question 7: Process Flow Chart Design, Hazard/Control Identification at Each Step, and an Alternate Hazard-Reduced Flow Chart (20 marks: 7/7/6)

(i) Original Process Flow Chart — Sheet-Metal Stamping and Coating Line (7 Steps)

(ii) Hazards and Controls at Each Step

(iii) Alternate Process Flow Chart Reducing the Number of Hazards