--- title: "Risk, society and design standards" subject: "Machine Design II" chapter: 4 key: "semester_7/machine_design_ii:risk-society-standards-regulation" source: https://www.bctengineer.com/q/semester_7/machine_design_ii/risk-society-standards-regulation site: BCT Engineering --- # Risk, society and design standards Machine Design II · Chapter 4: Risk and Reliability of Design - Asked in: year not given, 6 marks - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/machine_design_ii/risk-society-standards-regulation - Whole chapter: https://www.bctengineer.com/md/semester_7/machine_design_ii/chapter-4 ## Question Define risk. Explain how society views risk, the role of regulations and standards in controlling it, and the steps of a risk assessment for a machine. ## Short answer Risk = probability × consequence. Society tolerates voluntary risks more than involuntary ones and fears rare catastrophic events. Regulations and standards set minimum safety rules. Risk assessment steps: define limits, identify hazards, estimate likelihood and severity, evaluate acceptability, then reduce risk through design, guards, warnings, and PPE. ## Answer **Risk** is the combination of the probability that a hazard causes harm and the severity of that harm: $\text{Risk} = \text{probability} \times \text{consequence}$. Zero risk is impossible, so designers aim for risk that is **as low as reasonably practicable (ALARP)**. #### Risk and society - People accept **voluntary** risks (driving, climbing) more easily than **involuntary** ones (a dam or chemical plant nearby). - Rare events with large consequences (aircraft crash, bridge collapse) are feared more than common small ones, though total harm may be less. - Acceptance depends on benefit, familiarity, control and trust. Engineers have an ethical duty to protect public safety, health and welfare before cost. #### Regulations and standards - **Regulations/laws** are legally binding (safety acts, boiler, pressure vessel and lift rules, building codes). - **Standards and codes** (ISO, IEC, ASME, IS, NS) give accepted minimum design rules, factors of safety, test methods and dimensions; following them also helps in liability defence. - **Product liability** puts responsibility on the designer and maker for defects and missing warnings. #### Risk assessment steps 1. Define the machine limits, use and misuse. 2. **Identify hazards** (crushing, shearing, entanglement, high pressure, noise). 3. **Estimate risk:** likelihood (exposure, probability of event, chance to avoid) and severity. 4. **Evaluate** against criteria: acceptable or not. 5. **Reduce risk** in order: eliminate by design, use guards and protective devices, then warnings and training, then personal protective equipment. 6. Document, review and repeat after any change. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. How is risk defined? A. Severity of harm alone B. Probability alone C. Probability that a hazard causes harm multiplied by the severity of that harm D. The cost of the machine Answer: C. Risk = probability x consequence, and zero risk is impossible so designers aim for ALARP. (Key point: Definition of risk) 2. What does ALARP aim for? A. Zero risk at any cost B. Risk as low as reasonably practicable C. The cheapest design D. Accepting all voluntary risks Answer: B. Because zero risk is impossible the aim is risk as low as reasonably practicable. (Key point: ALARP) 3. How do people usually view voluntary and involuntary risks? A. Voluntary risks such as driving are accepted more easily than involuntary ones such as a chemical plant nearby B. Involuntary risks are accepted more easily C. Both are treated the same D. Only rare events are accepted Answer: A. Acceptance depends on choice, benefit, familiarity, control and trust. (Key point: Society's view of risk) 4. In which order should risk be reduced in a machine? A. PPE first, then warnings, then guards B. Training, then PPE, then design C. Warnings, then design, then guards D. Eliminate by design, then guards and protective devices, then warnings and training, then PPE Answer: D. The hierarchy removes the hazard at source first and relies on people-dependent measures last. (Key point: Order of risk reduction) ## Related in Machine Design II - [Role and types of models in design](https://www.bctengineer.com/question.md?key=semester_7%2Fmachine_design_ii%3Amodels-role-engineering-design) — Machine Design II, chapter 1 - [Power screw threads, standards and materials](https://www.bctengineer.com/question.md?key=semester_7%2Fmachine_design_ii%3Ascrew-thread-types-standards-stress) — Machine Design II, chapter 8 - [Six-speed machine tool gearbox design](https://www.bctengineer.com/question.md?key=semester_7%2Fmachine_design_ii%3Amachine-tool-speed-ladder-gear) — Machine Design II, chapter 5 - [FEM steps and geometric modelling](https://www.bctengineer.com/question.md?key=semester_7%2Fmachine_design_ii%3Afem-steps-geometric-modelling) — Machine Design II, chapter 1 - [Requirements of machine tool drives](https://www.bctengineer.com/question.md?key=semester_7%2Fmachine_design_ii%3Amachine-tool-drive-requirements) — Machine Design II, chapter 5 - [Casting versus forging design considerations](https://www.bctengineer.com/question.md?key=semester_7%2Fmachine_design_ii%3Acasting-forging-design-differences) — Machine Design II, chapter 3 ## Related in other subjects - [Role of transportation in society](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Arole-of-transport) — Transportation Engineering I, chapter 1, asked 3× - [Role of electrical energy in modern society](https://www.bctengineer.com/question.md?key=semester_7%2Futilization_of_electrical_energy%3Arole-electrical-energy-modern-society) — Utilization of Electrical Energy, chapter 1 - [Risk management and its steps](https://www.bctengineer.com/question.md?key=semester_7%2Fproject_engineering%3Arisk-management-define-steps) — Project Engineering, chapter 5, asked 2× - [Risk, sources of risk, risk management steps](https://www.bctengineer.com/question.md?key=semester_7%2Fproject_engineering%3Arisk-define-sources-steps) — Project Engineering, chapter 5