Safety and Hazards

Safety engineering is about showing, with evidence, that the hazards a system could create have been found, reduced as far as is reasonable and kept under control through design, construction, handover and operation. It draws on hazard identification, safety requirements, integrity targets and a clear legal test for when risk is low enough.

This hub is for systems, safety and project engineers who need to run a hazard log, write safety requirements or build an assurance case. It starts with the core ideas, then covers safety integrity levels and progressive assurance, residual risk and its transfer at handover, safety on construction projects, and the growing overlap between safety and cyber security in connected systems.

Start here

• What is a hazard log? — the purpose and contents of a hazard log, and best practice for keeping it live
• Safety requirements — what makes a requirement a safety requirement and how it links to hazard control
• Safety assurance step by step — how to monitor, record and evaluate safety performance within a Safety Management System
• SFAIRP vs ALARP — how the two risk-reduction principles differ in law and practice, and what that means

Safety integrity and progressive assurance

Integrity targets say how reliable a safety function must be, and progressive assurance builds the evidence as the project goes.

• Safety Integrity Level (SIL) calculation — a worked tank-overfill example with the 1oo1 PFDavg formula and SIL 1-4 ranges
• Progressive assurance — the processes used to assure safety, reliability and quality of complex systems progressively

Residual risk and risk transfer

Some risk always remains, and it has to be handed from builder to operator knowingly.

• Residual risk and risk transfer — how residual safety risks pass from construction through handover into the operational phase

Construction safety

Construction sites carry their own hazards and their own expectations for safety assurance.

• Construction hazards and controls — falls, plant, electricity and materials, and how a structured approach assesses and controls them
• Safety assurance on construction projects — what proving that a construction project’s safety risks are controlled involves

Safety and security

In connected systems a security breach can become a safety failure, so the two must be engineered together.

• Safe and secure cyber-physical systems — engineering safety and security together using IEC 62443, ISO 21434 and TARA

Related hubs: reliability, availability and maintainability (RAMS), requirements engineering, systems engineering. See also: RAMS and safety, FMECA, operational readiness and handover.