A HAZOP study can only be as good as the information available to the study team. Incomplete, outdated, or unclear documentation leads to weak discussions, missed hazards, and unreliable recommendations. Collecting the right data and documents, properly identified and approved, is therefore a critical preparation step for any HAZOP study.
All documents used in the study should be clearly identified, approved, and dated to ensure the team is working with accurate and consistent information.
Core Documentation Required for All Systems
Regardless of the system type, certain information is always required.
This includes:
- Design intent and operating philosophy
- Functional requirements of the system
- Overall system description and scope
These documents define what the system is supposed to do and form the reference point for identifying deviations.
Documentation for Hardware-Based Systems
For systems involving physical equipment, detailed engineering documents are essential.
Typical documents include:
- Process and flow sheets
- Functional block diagrams
- Control and interlock diagrams
- Interface diagrams
- Electrical circuit diagrams
- Engineering data sheets
- General arrangement drawings
- 3D models (where available)
- Utility specifications
- Operating and maintenance requirements and instructions
These documents help the team understand equipment behavior, interfaces, and dependencies.
Documentation for Process Flow Systems
Process flow systems require a strong focus on piping, instrumentation, and materials.
Commonly required documents include:
- Piping and Instrumentation Diagrams (P&IDs)
- Process flow diagrams
- Material specifications and standards
- Equipment specifications
- Piping layouts and system layouts
These are the primary working documents during most process HAZOP studies.
Documentation for Programmable Electronic Systems
For systems involving software, automation, or digital control, logic and data flow must be clearly documented.
Typical documents include:
- Data flow diagrams
- Object-oriented design diagrams
- State transition diagrams
- Timing diagrams
- Logic diagrams
These documents allow the team to assess software behavior, logic failures, and unsafe system responses.
Documentation for Procedures and Document-Based Systems
When HAZOP is applied to procedures or documentation, the focus shifts from hardware to activities and information flow.
Required inputs may include:
- Draft procedures or instructions
- Operating manuals
- Emergency and maintenance procedures
- Results of task analyses
- Operational breakdown matrices
This information supports the identification of human and procedural weaknesses.
Additional Supporting Information
To strengthen the study, additional contextual information should be provided where available.
This may include:
- System boundaries and interface definitions
- Description of internal and external operating environments
- Operating and maintenance arrangements
- User interface design information
- Historical experience with similar systems or past incidents
Such information helps the team place hazards in realistic operating context.
Why Proper Documentation Matters?
- Ensures consistent understanding across the team
- Improves quality and depth of discussions
- Reduces time wasted clarifying missing information
- Leads to credible, defensible recommendations
Poor documentation is one of the most common reasons for ineffective HAZOP studies.
Certified Functional Safety Professional (FSP, TÜV SÜD), Certified HAZOP & PHA Leader, LOPA Practitioner, and Specialist in SIL Verification & Functional Safety Lifecycle, with 18 years of professional experience in Plant Operations and Process Safety across Petroleum Refining and Fertilizer Complexes.
