Inherently Safer Design: What, When and Why?
An exploration of the inherently safer design (ISD) philosophy used across high-hazard industries. We explain what ISD entails, why it should be implemented early in a project's lifecycle, and the advantages of proactively removing or reducing hazards at the source.
Inherently Safer Design (ISD) refers to a fundamental safety philosophy aimed at eliminating or significantly reducing hazards at their source rather than relying on add-on engineering controls. This concept, popularised by Trevor Kletz, emerged in response to major industrial incidents like the Flixborough explosion in 1974. By adopting ISD principles, high-hazard industries—including oil and gas, chemical, hydrogen, nuclear, and carbon capture—can systematically remove risk where possible, rather than trying to manage it later with complex safeguarding systems.
Principles of Inherently Safer Design
There are four core strategies central to ISD:
- Minimisation: Reducing the quantity of hazardous substances. For instance, storing only the needed quantity of a toxic material rather than keeping large bulk stocks.
- Substitution: Replacing a hazardous material or process with a less dangerous alternative. An example is employing water-based solutions over flammable solvents when feasible.
- Moderation: Using milder operating conditions, such as lower pressures or temperatures, to reduce the energy involved in a process.
- Simplification: Eliminating unnecessary complexity in equipment or procedures, thus reducing the potential for errors and accidents.
Ideal Timing for ISD
ISD offers the greatest benefit when applied early in a project’s lifecycle, such as during the conceptual design phase or Front-End Engineering Design (FEED). Changes at these stages can be implemented more cost-effectively than retrofits later on, enabling safer process choices—like selecting less hazardous raw materials or designing equipment for lower operating conditions—before layouts and procurement are finalised.
Case studies often reveal that projects integrating ISD from the outset report fewer incidents, lower insurance premiums, and reduced lifecycle costs due to simpler, more robust designs. Retrofits can still introduce inherently safer strategies, but the impact is generally less pronounced and more expensive.
Benefits of Inherent Safety
- Reduced Risk Profile: Removing or lessening hazards at the source naturally lowers the magnitude of potential incidents.
- Lower Operating Costs: Designing hazards out minimises the need for complex safety systems, lowering maintenance and operational overhead.
- Streamlined Compliance: With fewer hazards to regulate, it often becomes more straightforward to meet or exceed legislative requirements.
Ultimately, the proactive adoption of ISD across high-hazard sectors not only enhances safety but also fosters a culture of continuous improvement and responsible innovation.
