Industrial safety and maintenance

In short

Industrial safety is the systematic prevention of injury, illness, fire and property loss in a workplace; maintenance is the set of actions that keeps plant and equipment in a condition where it performs its function safely and economically. The two are inseparable — most industrial accidents happen on neglected equipment or during repair work, and most unplanned downtime is a maintenance failure. Examination of this topic covers accident causation and costing, hazard identification techniques (HAZOP, FMEA, FTA), statutory duties under the Occupational Safety, Health and Working Conditions Code, 2020 (in force from 21 November 2025; it repealed the Factories Act 1948, whose section numbers older papers still quote as the former law), maintenance classification, TPM and OEE. It is examined in industrial engineering papers, GATE (ME/PI) and the Diploma in Industrial Safety, and asked in interviews for safety officer, maintenance engineer, plant engineer and EHS roles at Tata Steel, L&T, Reliance, BPCL, NTPC, Maruti Suzuki and the chemical and pharma sector.

Explained

Basic terms and accident causation

• Hazard: an inherent property or condition with potential to cause harm. Risk: combination of the likelihood of harm and its severity. Danger is the relative exposure to a hazard.
• Incident / near-miss: an unplanned event with no injury; accident: an unplanned event causing injury, illness or loss. Reportable (lost-time) injury: absence beyond the prescribed period — an injury that prevents the person working for 48 hours or more immediately after the accident must be notified under section 10 of the OSH Code, 2020 (the same 48 hours as former s. 88 of the repealed Factories Act).
• Unsafe act (operator removing a guard, by-passing an interlock) versus unsafe condition (broken ladder, exposed live conductor). Both must be addressed; blaming only the act stops at the symptom.
• Heinrich's domino theory: ancestry/social environment → fault of person → unsafe act or condition → accident → injury; removing the middle domino breaks the sequence. Heinrich's ratio 1 : 29 : 300 (major : minor : no-injury incidents) and his claim that 88% of accidents arise from unsafe acts.
• Bird's accident triangle: 1 serious : 10 minor : 30 property-damage : 600 near-misses — the basis of near-miss reporting.
• Modern view: multi-causal — latent organisational failures line up with active errors (Reason's Swiss-cheese model). Hence root-cause analysis (5-Why, fishbone, FTA) rather than single-cause blame.
• Hierarchy of controls, in order of effectiveness: (1) elimination, (2) substitution, (3) engineering controls (guards, interlocks, ventilation, enclosure), (4) administrative controls (procedures, training, job rotation, signage), (5) PPE — the last and weakest line.

Hazard identification and risk assessment techniques

• Checklist and what-if analysis: quick, experience-based screening for standard plant; cheap but misses novel hazards.
• Preliminary hazard analysis (PHA): done at design concept stage to rank hazards before layout is frozen.
• JSA / JHA (job safety analysis): break a job into steps, list the hazard of each step, assign a control. Basis of safe operating procedures.
• HAZOP (hazard and operability study): a team examines each node of a P&ID, applying guide words — NO/NONE, MORE, LESS, AS WELL AS, PART OF, REVERSE, OTHER THAN — to parameters (flow, pressure, temperature, level, composition) to find deviations, causes, consequences and safeguards. Standard for chemical, refinery and pharma plants; qualitative and manpower-intensive.
• FMEA / FMECA: for each component list failure mode, effect, cause, detection; score Severity, Occurrence, Detection (1–10) and compute RPN = S × O × D. Bottom-up, single-failure oriented.
• Fault tree analysis (FTA): top-down, starts from an undesired top event and develops causes through AND / OR gates to basic events; gives the probability of the top event. Event tree analysis is the forward complement (consequences of an initiating event). Bow-tie joins the two.
• QRA (quantitative risk assessment): frequency × consequence modelling (dispersion, fire radiation, overpressure) to produce individual and societal risk; required for MAH (major accident hazard) units.
• Risk matrix: likelihood × severity grid classifying risk as low / medium / high with required action levels; ALARP — reduce risk as low as reasonably practicable.
• Safety audit: systematic independent examination of systems against a checklist — IS 14489 is the Indian code of practice for occupational safety and health audit; IS 15656 covers hazard identification and risk analysis. ISO 31000 gives the generic risk-management framework.

Indian statutes, codes and institutions

• Occupational Safety, Health and Working Conditions Code, 2020 (OSH Code, Act 37 of 2020) — the law on factory safety, health and working conditions since 21 November 2025, when it came into force with the other three Labour Codes. It consolidates 13 central laws and section 143 repealed them, including the Factories Act 1948, the Mines Act 1952, the Contract Labour Act 1970 and the BOCW Act 1996. Under the savings in s. 143(3), rules, notifications and orders made under the repealed Acts — notably each State's Factories Rules — continue, so far as not contrary to the Code, until replaced by rules under it. The OSH&WC (Central) Rules, 2026 (8 May 2026) apply where the Central Government is the appropriate Government; for most factories the State Government is, and States are notifying their own OSH rules one by one, so check the State's current rules before quoting a number.
• Code structure (factory-relevant sections): factory defined in s. 2(1)(w) — 20 or more workers with power, 40 or more without (10 / 20 under the former Act); duties of employer s. 6 (workplace free from hazards, free annual health examination, appointment letters — successor of former s. 7A); duties of designers, manufacturers, importers and suppliers s. 8; notice of accidents s. 10, of dangerous occurrences s. 11 and of notifiable diseases s. 12 (Third Schedule); duties and rights of employees ss. 13–14; National and State OSH Advisory Boards ss. 16–17; occupational safety and health standards s. 18, on the matters listed in the Second Schedule (fencing of machinery, hoists and lifts, pressure plant, fire and similar); safety committee and safety officers s. 22; employer's responsibility for health, safety and working conditions s. 23; welfare facilities s. 24; penalties Chapter XII (ss. 94–114).
• Safety officers (s. 22(2)) — required in factories with 500 or more workers, in factories carrying on a hazardous process with 250 or more, in building or other construction work with 250 or more and in mines with 100 or more (the former s. 40B threshold was 1,000 workers, or a notified hazardous process). Safety committee (s. 22(1)) — the appropriate Government may require one by notification, with representatives of workers and of the employer (formerly s. 41G for hazardous-process factories).
• Hazardous processes — Chapter XI, Part VII "Factories" (ss. 79–91), the successor of Chapter IV-A (former ss. 41A–41H) that the 1987 amendment inserted after the 1984 Bhopal disaster: approval and licensing of factories s. 79; dangerous operations s. 82; site appraisal committee s. 83; compulsory disclosure of information by the occupier, including the on-site emergency plan and disaster control measures s. 84; specific responsibility of the occupier in relation to hazardous processes — health records, qualified supervisors, medical examination before, during and after exposure s. 85; inquiry by the National Board s. 86; emergency standards s. 87; permissible limits of exposure of chemicals and toxic substances s. 88; right of workers to warn about imminent danger s. 89. "Hazardous process" is defined in s. 2(1) by reference to the First Schedule (industries involving hazardous processes). Breach of hazardous-process duties is punished under s. 102, and a safety contravention resulting in an accident under s. 103.
• Former Factories Act section scheme (repealed; still asked in older papers, so quote it as the former law): Chapter III (ss. 11–20) health; Chapter IV (ss. 21–41) safety — former s. 21 fencing of machinery, 22 work on machinery in motion, 23 young persons on dangerous machines, 24 striking gear, 28 hoists and lifts (examined every 6 months), 29 lifting machines and tackle (every 12 months), 31 pressure plant, 32 floors and means of access, 34 excessive weights, 35 eye protection, 36 dangerous fumes and confined spaces, 37 explosive or inflammable dust and gas, 38 fire, 40B safety officers; 88 / 88A notice of accidents and dangerous occurrences. Under the Code these detailed duties are no longer sections of the statute: they sit in standards under s. 18 and in the rules, and the examination intervals in the State Factories Rules continue under s. 143(3) until State OSH rules replace them.
• Welfare (s. 24): first-aid facilities in every establishment; canteen where 100 or more workers are employed; creche where 50 or more employees are employed (s. 24(3)); a welfare officer in a factory, mine or plantation with 250 or more workers (s. 24(2)(iv)); first-aid box scales and ambulance rooms are fixed by the rules. (Former Act: first-aid box per 150 workers, ambulance room above 500, canteen at 250, welfare officer at 500.)
• Sector and hazard-specific law: mines safety with DGMS (the Mines Act 1952 is now subsumed in the OSH Code, 2020); Boilers Act 2025 (in force from 1 May 2025, replacing the Boilers Act 1923) and the Indian Boiler Regulations, 2026 (October 2026, superseding the Indian Boiler Regulations 1950); Explosives Act 1884, Petroleum Act 1934 and Gas Cylinders Rules 2016 administered by PESO; Electricity Act 2003 with the CEA (Measures relating to Safety and Electric Supply) Regulations, 2023 (8 June 2023, superseding the 2010 Regulations, which had replaced the Indian Electricity Rules, 1956); Environment (Protection) Act 1986 with MSIHC Rules 1989 and Chemical Accidents (EPPR) Rules 1996; Public Liability Insurance Act 1991; the Code on Social Security, 2020 (in force from 21 November 2025; it repealed and absorbed the Employee's Compensation Act 1923 and the ESI Act 1948).
• Institutions: DGFASLI (advisory, under the Ministry of Labour and Employment), State Chief Inspector of Factories / Inspectorate (enforcement), NSCI (National Safety Council of India, promotional — National Safety Day on 4 March), BIS for IS standards, NDMA for disaster plans.
• Management systems: ISO 45001:2018 (OH&S management system, Plan-Do-Check-Act, replaced OHSAS 18001), ISO 14001 (environment), ISO 55001 (asset management). IS 9457 covers safety colours and signs (red — prohibition/fire, yellow — warning, green — safe condition, blue — mandatory).

Specific hazards and their control

• Mechanical: entanglement in rotating shafts, in-running nips, shear and crush at press tools. Guards: fixed, interlocked (power cut when opened), automatic/sweep, trip (light curtain, pressure mat), two-hand control, plus emergency stop, hold-to-run and anti-repeat devices on presses.
• Electrical: shock, burns, arc flash, fire. Controls — earthing to IS 3043, double insulation, ELCB/RCD of 30 mA for personnel protection, correct fuses/MCBs, 24 V hand lamps in confined spaces and tanks, work only on dead circuits under LOTO, insulated mats and rubber gloves, hazardous-area classification (Zone 0/1/2 per IEC/IS 60079) with flameproof fittings.
• Fire and explosion: fire triangle (fuel, oxygen, heat) extended to the tetrahedron (chain reaction). Extinguishing works by cooling (water), smothering (foam, CO₂), starvation (isolating fuel) or chain-breaking (dry chemical powder, clean agents). Indian classes — A solids, B flammable liquids, C flammable gases, D combustible metals, F cooking media; electrical fires are fought with non-conducting media (CO₂, DCP, clean agent), never water jets. Key concepts: flash point, auto-ignition temperature, LEL/UEL flammability limits, flame arrestors, BLEVE. Provisions follow the National Building Code 2016 Part 4 and IS 2190 (selection and maintenance of portable extinguishers).
• Chemical and health: routes of entry (inhalation, skin, ingestion); controls by substitution, total enclosure, local exhaust ventilation; MSDS/SDS, labelling, permissible exposure limits under s. 88 of the OSH Code, 2020 (formerly the Second Schedule of the repealed Factories Act); medical examination and health records for hazardous processes.
• Noise: the Model Factories Rules schedule, carried in State Factories Rules that continue under s. 143(3) of the OSH Code until State OSH rules replace them, permits 90 dB(A) for 8 hours, with no unprotected exposure above 115 dB(A) and an impulse-noise ceiling of 140 dB peak; control at source (enclosure, damping, silencers), then administrative limits on exposure time, then hearing protection.
• Confined space: permit entry only after isolation, purging, gas testing for oxygen (19.5–23.5%), flammables and toxics, continuous ventilation, standby person outside, rescue harness, low-voltage lighting — now under OSH standards and rules made under the Code (formerly s. 36 of the repealed Factories Act).
• Work at height, material handling, pressure systems: full-body harness with double lanyard above 1.8 m, scaffolding checks, edge protection; trained operators, load charts and tested tackle for cranes; statutory inspection and relief-valve testing for pressure vessels and boilers.
• Administrative systems: permit-to-work (hot work, cold work, electrical, excavation, height, confined space), LOTO (lock-out/tag-out) with personal locks, gas-freeing certificates, contractor safety induction, toolbox talks, mock drills, on-site emergency plan, incident reporting and investigation.

Maintenance: types and organisation

• Breakdown / corrective (reactive) maintenance: repair after failure. Lowest planning cost, highest consequential cost; acceptable only for cheap, non-critical, redundant items.
• Preventive maintenance (PM): planned action before failure — time-based (calendar) or use-based (running hours, cycles, km). Includes lubrication, cleaning, inspection, calibration, scheduled replacement and overhaul. Reduces unplanned downtime but can replace healthy parts.
• Predictive / condition-based maintenance (CBM): act on measured condition — vibration analysis (severity zones of ISO 10816/20816; FFT spectra identify unbalance at 1×, misalignment at 2×, bearing defect frequencies), infrared thermography (hot joints, overloaded motors), lubricating-oil and wear-debris analysis (ferrography), ultrasonic leak and bearing testing, motor current signature analysis, NDT (dye penetrant, UT, radiography), thickness surveys. Highest instrument and skill cost, lowest total cost on critical machines.
• Proactive / design-out maintenance: remove the root cause by redesign, better material, or a different lubricant so the failure cannot recur.
• Opportunity, shutdown and scheduled overhaul maintenance: work done when the plant is already stopped; annual turnaround in refineries and fertiliser plants.
• RCM (reliability-centred maintenance, SAE JA1011): function → functional failure → failure mode → effect → consequence (safety, environment, operational, non-operational) → task selection. Produces a justified mix of PM, CBM, failure-finding tests and redesign instead of blanket time-based PM.
• Organisation and control: centralised versus decentralised (area) maintenance; work-order system, job cards, equipment history, planning and scheduling, backlog control, CMMS/ERP modules such as SAP PM; spare-parts policy using ABC (value) and VED (vital–essential–desirable) classification plus insurance spares for long-lead critical items.
• Maintainability is designed in: accessibility, standardisation, modular replacement, built-in diagnostics, quick-release fasteners.

TPM, OEE and the safety–maintenance link

• TPM (total productive maintenance), developed in Japan — Nippondenso was its first implementer (1971) and Seiichi Nakajima of JIPM is credited as its father: productive maintenance carried out by all employees, aiming at zero breakdowns, zero defects and zero accidents, built on 5S.
• Eight pillars: autonomous maintenance (Jishu Hozen), planned maintenance, focused improvement (Kobetsu Kaizen), quality maintenance, early equipment management, education and training, office TPM, and safety, health and environment — safety is an explicit pillar, not an add-on.
• Autonomous maintenance transfers cleaning, lubrication, bolt-tightening and basic inspection to operators, since cleaning is inspection and most failures begin with contamination, poor lubrication or loose fasteners.
• Six big losses attacked by TPM: breakdown; setup and adjustment; idling and minor stoppages; reduced speed; defects and rework; start-up/yield loss. The first two destroy availability, the next two performance, the last two quality.
• OEE (overall equipment effectiveness) = Availability × Performance × Quality; the common world-class benchmark is about 85% (90 × 95 × 99.9).
• Why maintenance is a safety matter: a large share of serious accidents occur during maintenance and repair — isolation not done, guard left off after a job, defeated interlock, scaffolding or crane tackle not examined. Statutory inspections (hoists and lifts, lifting tackle, pressure vessels, boilers, relief valves, earth-resistance tests) are legally maintenance tasks.
• Leading versus lagging indicators: lagging — frequency rate, severity rate, lost-time injuries; leading — near-misses reported, PM compliance, audit findings closed, training hours, safety observations. A plant with zero injuries but 20% PM compliance is not safe, only lucky.

Key points

• Hazard vs risk — hazard is the potential to harm; risk is likelihood × severity of that harm being realised.
• Hierarchy of controls — elimination, substitution, engineering, administrative, PPE; PPE is always last.
• Heinrich's ratio — 1 major : 29 minor : 300 no-injury incidents; near-misses are free lessons.
• OSH Code 2020 — in force from 21 November 2025; consolidates 13 laws and repealed them (s. 143), including the Factories Act 1948; factory threshold 20/40 workers (s. 2(1)(w)); State Factories Rules continue under s. 143(3) until State OSH rules replace them.
• Safety officers (s. 22(2)) — 500+ workers, or 250+ in a hazardous-process factory (former s. 40B: 1,000); safety committee (s. 22(1)) on Government notification.
• Hazardous processes — Chapter XI Part VII, ss. 79–91 (site appraisal s. 83, disclosure and on-site emergency plan s. 84, occupier's responsibility s. 85, exposure limits s. 88, right to warn s. 89); the former Chapter IV-A (ss. 41A–41H) was added in 1987 after Bhopal.
• HAZOP — guide words applied to P&ID nodes; the standard process-plant hazard study.
• FMEA — RPN = Severity × Occurrence × Detection, each rated 1–10, maximum 1000.
• FTA — top-down with AND/OR gates giving top-event probability; event tree is the forward view.
• Machine guards — fixed, interlocked, automatic, trip; interlock must cut power when the guard opens.
• Fire classes (India) — A solids, B liquids, C gases, D metals, F cooking media; use non-conducting agents on electrical fires.
• Permit-to-work and LOTO — isolate, lock, tag, try; the primary defences for maintenance work.
• Maintenance types — breakdown, preventive, predictive/condition-based, proactive/design-out; RCM selects the right mix per failure mode.
• Condition monitoring tools — vibration, thermography, oil analysis, ultrasonics, motor current signature.
• TPM — eight pillars, operator-owned autonomous maintenance, target zero breakdown/defect/accident.
• OEE — Availability × Performance × Quality; six big losses; ~85% is world class.
• IS 3786 — Indian method for computing injury frequency and severity rates; a fatality carries a scheduled charge of 6,000 days.
• ISO 45001:2018 — PDCA-based OH&S management system standard, replaced OHSAS 18001.

Formulas and examples

Units: man-hours in hours actually worked (not paid); FR and SR are per million man-hours; days lost in calendar days charged; costs in rupees.

Example 1 — Safety statistics for a plant. A factory employs 500 workers who each work 48 hours a week for 50 weeks. In the year there were 9 lost-time injuries, one of them fatal. Days lost on the eight non-fatal cases total 240; the fatality is charged 6,000 days.

• Man-hours worked = 500 × 48 × 50 = 1,200,000
• FR = 9 × 1,000,000 / 1,200,000 = 7.5 injuries per million man-hours
• Days charged = 6,000 + 240 = 6,240 → SR = 6,240 × 1,000,000 / 1,200,000 = 5,200
• Incidence rate = 9 × 1,000 / 500 = 18 per 1,000 workers
• Average days charged per injury = 5,200 / 7.5 ≈ 693 (inflated by the fatality charge — always report FR and SR together)
• FSI = √(7.5 × 5,200 / 1,000) = √39 ≈ 6.24

Example 2 — Has safety improved? Last year FR was 10.0; this year the plant worked 1,200,000 man-hours and FR fell to 7.5.

• STS = (7.5 − 10.0) / √(10.0 ÷ 1.2) = −2.5 / √8.333 = −2.5 / 2.887 = −0.87
• |STS| < 2, so the fall is not statistically significant — one year's drop is within normal variation, not proof that the controls worked.

Example 3 — Cost of one accident. A machine-guarding accident costs the firm ₹1,20,000 in direct costs (compensation, medical, insurance excess). Using Heinrich's 1:4 ratio, indirect costs (lost production, overtime, investigation, retraining, damaged tooling, legal and reputation) ≈ 4 × 1,20,000 = ₹4,80,000; total ≈ ₹6,00,000. If the firm's profit margin is 4%, sales of 6,00,000 / 0.04 = ₹1.5 crore are needed to recover it — while the interlocked guard that would have prevented it costs about ₹25,000.

Example 4 — OEE of a CNC machine. Shift of 8 hours (480 min) with a 30-minute planned lunch break. Breakdown 30 min, setup 15 min. Ideal cycle time 0.5 min/part; 720 parts produced, 18 rejected.

• Loading time = 480 − 30 = 450 min; downtime = 45 min; operating time = 405 min
• Availability = 405 / 450 = 0.900
• Performance = (0.5 × 720) / 405 = 360 / 405 = 0.889
• Quality = (720 − 18) / 720 = 702 / 720 = 0.975
• OEE = 0.900 × 0.889 × 0.975 = 0.780 → 78.0% (equivalent to 351 good minutes out of 450). Below the 85% benchmark; the biggest single loss here is speed/minor stoppages.

Example 5 — Optimum preventive-maintenance interval. A PM service costs ₹20,000; a breakdown costs ₹50,000 including lost output. Expected breakdowns per year rise as the interval lengthens:

The U-shaped total cost is lowest at a 2-month interval (₹2,45,000 per year) — a saving of ₹2,05,000 against run-to-failure. Note that if the failure mode is safety-critical, the interval is set by the risk, not by this cost minimum.

Where it is used

• Process and chemical industry: HAZOP and QRA at design, MSIHC compliance, on-site emergency plans and shutdown turnarounds at refineries and fertiliser plants (IOCL, BPCL, RIL, Deepak Nitrite).
• Automotive and discrete manufacturing: TPM and OEE on assembly and machining lines, press-shop light curtains and two-hand controls, operator autonomous maintenance (Maruti Suzuki, Bajaj, Bosch, TVS — many plants hold JIPM TPM awards).
• Steel, cement and power: vibration and thermography routes on mills, fans and turbines; permit-to-work and LOTO for boiler and ESP work; statutory boiler and pressure-vessel inspections (Tata Steel, NTPC, UltraTech).
• Construction and infrastructure: work-at-height harness discipline, scaffolding checks, crane load charts, OSH Code compliance (formerly the BOCW Act) on metro and highway projects (L&T, AFCONS).
• Job roles: safety officer and EHS manager (often a Diploma in Industrial Safety plus NEBOSH/IOSH), maintenance and reliability engineer, plant engineer, condition-monitoring analyst, factory inspector, loss-prevention engineer in insurance and third-party audit firms.
• Mines and ports: DGMS-regulated statutory inspections, gas testing and equipment examinations.

Interview questions

• Q: What is the difference between a hazard and a risk? A: A hazard is the inherent potential to cause harm; risk is the combination of how likely that harm is and how severe it would be. A guarded hazard still exists but the risk is low.
• Q: State the hierarchy of controls and why PPE is last. A: Elimination, substitution, engineering, administrative controls, then PPE. PPE protects only the wearer, only if worn correctly and maintained, and leaves the hazard untouched.
• Q: What is a HAZOP and what are guide words? A: A structured team study of each node of a P&ID using guide words (NO, MORE, LESS, AS WELL AS, PART OF, REVERSE, OTHER THAN) against parameters like flow and pressure to identify deviations, causes, consequences and safeguards.
• Q: How is RPN calculated and what is its weakness? A: RPN = Severity × Occurrence × Detection, each 1–10. The scales are ordinal, so equal RPNs are not equally important — a severity-10 item needs action even at a low RPN.
• Q: How do you compute frequency rate and severity rate? A: FR = lost-time injuries × 10⁶ / man-hours worked; SR = days lost or charged × 10⁶ / man-hours worked, following IS 3786, which charges 6,000 days for a fatality or permanent total disability.
• Q: Which provisions now deal with hazardous processes in factories? A: Part VII of Chapter XI of the OSH Code, 2020 (sections 79–91), in force since 21 November 2025: site appraisal committee (s. 83), disclosure of information and the on-site emergency plan (s. 84), the occupier's specific responsibility (s. 85), permissible exposure limits (s. 88) and the worker's right to warn of imminent danger (s. 89), with safety committees under s. 22(1). They succeed Chapter IV-A (former ss. 41A–41H) of the repealed Factories Act, added in 1987 after Bhopal.
• Q: What is LOTO and why is tagging alone not enough? A: Lock-out/tag-out isolates and physically locks an energy source during maintenance; a tag is only information and can be ignored or removed, whereas each worker's personal lock makes re-energising impossible.
• Q: Difference between preventive and predictive maintenance? A: Preventive acts at a fixed time or usage interval regardless of condition; predictive acts on measured evidence of deterioration such as vibration, oil condition or temperature, so healthy parts are not replaced.
• Q: Define OEE and name the six big losses. A: OEE = Availability × Performance × Quality. The losses are breakdowns, setup and adjustment, idling and minor stoppages, reduced speed, defects and rework, and start-up/yield loss.
• Q: Why does TPM make operators do maintenance? A: Operators are closest to the machine; cleaning, lubricating and tightening (autonomous maintenance) catch the contamination and loose fasteners that cause most failures, and free skilled technicians for planned and predictive work.
• Q: Your plant reports zero accidents this year. Is it safe? A: Not necessarily — zero lagging injuries can be luck or under-reporting. I would check leading indicators: near-misses reported, PM compliance, audit actions closed, permit quality and training coverage.
• Q: Which extinguisher would you use on a live electrical panel fire, and why not water? A: CO₂, dry chemical powder or a clean agent, because water conducts and would risk electrocution and damage; isolate the supply first if possible.

Common mistakes

• Reporting frequency rate alone, or mixing up the denominators — FR and SR are per million man-hours, incidence rate is per 1,000 workers; using paid hours instead of hours actually worked also skews it.
• Forgetting the 6,000-day scheduled charge for a fatality, or reporting SR of a fatal year as if the days were actual absence.
• Listing PPE as the control for a guarding or electrical hazard when an engineering control exists — a marked loss of marks and the commonest interview trap.
• Confusing FMEA with FTA: FMEA is bottom-up from component failure modes, FTA is top-down from an undesired top event with logic gates.
• Treating preventive maintenance as always better than breakdown maintenance; for cheap, redundant, non-critical items run-to-failure is the economic choice, and over-frequent intervention introduces its own infant-mortality failures.
• Multiplying OEE factors after computing availability on total shift time instead of loading time (planned production time), or using actual cycle time instead of ideal cycle time in the performance factor.
• Quoting the repealed Factories Act's section numbers and thresholds as current law — since 21 November 2025 the OSH Code, 2020 applies (safety officers at 500 workers, not 1,000); and many numbers are fixed by State rules, where the old State Factories Rules continue under s. 143(3) only until each State's OSH rules replace them.

Related topics

Maintenance and reliability engineering · Statistical quality control · Lean manufacturing and Six Sigma · Work study and ergonomics · Production planning and control · Engineering economics and costing