HAZOP method, deviation analysis

The Hazard and Operability analysis (HAZOP) was developed by Imperial Chemical Industry in 1963. At first, it was established for chemical industries, in order to evaluate risks related to the possible deviations of a project. HAZOP is a systematic and structured method mainly used during the first deign produce. It is also regularly updated during the operating stage of the plant. The main theory assumes that deviation forms are triggered by the operating design and bring about risky events. This method enables to analyse possible deviations of a plant, their causes and consequences in order to mitigate risks. The plant’s operating parameters (pressure, temperature…) are associated with guide words (more, less, no for instance) so that risks can be revealed and quantified. As a consequence, the plant is reviewed in a safer, more reliable and more efficient way.

Part of a project’s risk management, this method optimises resources and brings about financial benefits to the plant’s owner (and operator). It highlights which control and safety systems are really required to the plant. The quickest HAZOP’s recommendations are applied in the design process, the most are the benefits. Nowadays many companies use this method to enhance their project management. It is particularly well suited to systems that employ material and energy flows.

History

HAZOP was initially thought for reviewing a new phenol plant design. The Heavy Organic Chemicals Division of the Imperial Chemical Industry (British and international company) conceived this method in 1963. At the beginning, it was based on a critical examination studying the alternatives of a system. Later, the method’s focus was altered in order to study system’s deviations after producing the first detailed design of the plant. The operability study method was created.

In 1977, ICI published a guide of this method officially named HAZOP. Since that date, the deviation analysis process has been applied in many projects from various types of company. Discussions and research have highlighted its usefulness in project management, but they have also unveiled some limits.

When to perform this method

The Hazard and Operability Analysis should be performed when the project members aim to check a design or running instructions; to decide the location of a construction; to decide whether to buy a piece of equipment; to obtain a list of questions to put to a supplier; or to improve the safety of existing facilities. Even though HAZOP is commonly used after the first design is complete, it can be applied while the system is operating. The main domains using this hazard analysis method are chemical, pharmaceutical, oil and gas companies.

This deviation analysis is best suited for assessing hazards in processes, equipment or facilities using energy and material flows. Risks related to a project can be assessed from at least three perspectives thanks to HAZOP:

• Design
  • Assess the system design capability to answer the user specifications, and to be in line with safety standards and guidelines
  • Identify system’s weaknesses
• Physical and operational environments
  • Assess the environment of the system to ensure that the location is appropriate in terms of places, thermal constraints, material near the installation (and possible danger with the operation) etc.
• Operational and procedural controls
  • Assess engineered controls, sequences of operations, procedural controls such as human interactions
  • Assess different operational modes such as the start and the shutdown of the system, the normal operation, the unsteady states of some functions, the emergency shutdown