Choosing between a HAZOP (Hazard and Operability Study) and a HAZID (Hazard Identification Study) depends on your project stage and the risk assessment objectives. Both are essential tools in process safety, but they serve very different purposes. Understanding HAZOP or HAZID will help you ensure hazards are identified early and safety is built into your process design.
What Is a HAZID and When Should You Carry It Out?
A HAZID (Hazard Identification) study is carried out early in the project lifecycle, typically during the feasibility stage, before detailed design. Its purpose is to proactively identify potential hazards related to safety, health, and the environment before the design becomes fixed.
By recognising major hazards early, organisations can:
- Influence key design decisions
- Reduce or eliminate hazards through inherent safety
- Optimise layouts and processes before significant investment
- Minimise future rework and costly redesign
A HAZID provides a high-level view of risks, ensuring major hazards are understood before progressing into detailed design.
What Is a HAZOP and When Is It Required?
A HAZOP (Hazard and Operability) study is a systematic, team-based review used to analyse process deviations, their causes, and their potential consequences. It is more detailed than a HAZID and is typically performed during the detailed design phase.
A HAZOP is usually carried out when:
- P&IDs (Piping and Instrumentation Diagrams) are available and well developed, with no major changes expected
- Modifications are planned on an existing system
- A project is progressing toward the final design stage
The aim of a HAZOP is to confirm:
- The design includes sufficient safeguards
- Risks are reduced to ALARP (As Low As Reasonably Practicable)
- Any design flaws, operability issues, or environmental impacts are identified
- Additional controls or changes are highlighted where risks are not adequately controlled
Who Should Be Part of the HAZID or HAZOP Team?
Both HAZID and HAZOP require a multidisciplinary team to ensure a comprehensive safety review. Having diverse expertise ensures that all hazard types, including safety, environmental, and operational, are properly assessed.
Typical team disciplines include:
- Process Engineering
- Process Safety
- SHE (Safety, Health & Environment)
- Operations
- Maintenance
- Project Management
- Control & Electrical Engineering
Each study should be led by an experienced Hazard Study Leader, responsible for facilitating structured analysis and guiding the team to well-justified conclusions. It is also better if there is a separate scribe for the HAZOP as leading a HAZOP and scribing at the same time can be extremely challenging and potentially impact the quality of the study. An experienced scribe can also bring additional engineering experience to the study.
Do You Still Need a HAZOP If You Already Completed a HAZID?
In most cases: Yes.
A HAZID and a HAZOP serve different purposes:
| Study | Project Stage | Purpose | Level of Detail |
|---|---|---|---|
| HAZID | Early design / concept stage | Identify broad, high-level hazards | Low to medium detail |
| HAZOP | Detailed design stage | Systematically assess deviations and safeguards | High detail |
A HAZID helps shape the early design, while a HAZOP ensures the final design is safe, operable, and compliant.
Completing both ensures hazards are managed proactively and systematically throughout the entire project lifecycle.
Why Both Studies Are Essential
Together, HAZID and HAZOP provide a robust approach to risk management by:
- Identifying hazards early
- Evaluating risks at appropriate design stages
- Ensuring safeguards meet ALARP principles
- Supporting safer and more reliable system operation
Applying the right study at the right time allows organisations to reduce overall project risk and improve operational safety performance.
Meet Our Expert: Vhari Shanks, Senior Process Safety Engineer
Vhari Shanks joined OTECSA in August last year (2024) as a Senior Process Safety Engineer. She brings extensive experience from upper-tier COMAH sites and previous engineering consulting roles. Vhari holds an MEng in Chemical Engineering from the University of Strathclyde.
Her specialisms include:
- Process design
- Operations support
- Plant troubleshooting
- Control system automation
- LOPA (Layer of Protection Analysis)
Her expertise strengthens our capability to deliver high-quality HAZID, HAZOP, and wider process safety services.
Need Support With a HAZOP or HAZID?
OTECSA Consulting provides independent, high-quality process safety services, including HAZID, HAZOP, LOPA, DSEAR assessments, and more.
If you would like support with a study or want to understand which approach is right for your project, our team is here to help.
Contact us to discuss your requirements.