HIRARC: HAZOP

HAZOP is an acronym for HAZard and OPerability studies. The term 'HAZOP' originated in ICI and first appeared in the literature in the early 1970s.

Skelton, B, (1997) defined it as a formal, systematic, critical, rigorous examination to the process and engineering intentions of new and existing facilities to assess the hazard potential of mal-operation or mal-function of individual items of equipment and the consequential effects. Wells, G, (1996),  HAZOP is formal, systematic examination of a processing plant in order to identify hazards, failures and operability problems, and assess the consequences from such mal-operation.

HAZOP will generates a list of identified problems, usually with some suggestions for improvement of the system. It will  improves safety, reliability and quality by making people more aware of potential problems. It also will help to sort out loopholes and inconsistencies

in procedures and force plant personnel to get their instructions up to date.

Basic philosophy of HAZOP; if a process operates within its intended design philosophy then undesired hazardous events should not occur. The objective of a HAZOP is mainly to identify how process deviations can be prevented or mitigated to minimize process hazards.

Basic Ideas of HAZOP are to stimulate the imagination of a review team, including designers and operators, in a systematic way so that they can identify potential hazards in a design; AND to let the mind go free in a controlled fashion in order to consider all the possible ways that

process and operational failures can occur.

Outcomes of HAZOP; to recommend necessary changes to a system to meet company risk guidelines, AND to recommend procedures or changes for eliminating or reducing the probability of operating deviations.

HAZOP used as an application at the correct stage in a project means that problems are identified and can be rectified during detailed design. It will provide a considerable amount of useful material for inclusion in the plant operating instructions.

HAZOP Terminology; (1) Design intent - the way in which the plant is intended to operate. (2) Deviation - any perceived deviations in operation from the design intent. Cause - the causes of the perceived deviations. (3) Consequence - the consequences of the perceived deviations. (4) Safeguards - existing provisions to mitigate the likelihood or consequences of the perceived deviations and to inform operators of their occurrence, (5) Actions - the recommendations or requests for information made by the study team in order to improve the safety and/or operability of the plant. (6) Guide words - simple words used to qualify the intent and hence discover deviations. (7) Parameters - basic process requirements such as 'flow', 'temperature', 'pres-sure' and so on.

HAZOP COMPONENTS are Team, Procedure and Guide words. HAZOP Team normally comprises between four and eight members,  each of whom can provide knowledge and experience appropriate to the project to be studied. The team needs to be small enough to be efficient and allow each member to make a contribution, whilst containing sufficient skills and experience to cover the area of study comprehensively.

Two types of person are required in a Hazop team: those with detailed technical knowledge of the process; AND those with knowledge and experience of the HAZOP technique and the ability to chair and report upon technical meetings.

typical member of a Hazop team are chairman or team leader, secretary, process design engineer, control engineer, operations specialist and project engineer. Other specialists may be consulted or be available for specific points.

Chairman or team leader is selected for his or her ability to effectively lead the study. He/she should have sufficient seniority to give the study recommendations the proper level of authority and has a knowledge and experience of the Hazop technique.

Secretary should have a technical appreciation of the project and be familiar with the HAZOP technique. The technical members are usually part of the project design team.

Hazop PROCEDURE

1. Begin with a detailed flow sheet. Break the flow sheet into a number of process units.  eg the reactor area might be one unit, and the storage tank another. Select a unit for study.

2. Choose a study node (vessel, line, operating instruction).

3. Describe the design intent of the study node. eg example, vessel V-I is designed to store the benzene feedstock and provide it on demand to the reactor.

4. Pick a process parameter( flow, level, temperature, pressure, concentration, pH, viscosity, power, Inert and etc.

5. Apply a guide word to the process parameter to suggest possible deviations.(NO, MORE, LESS, REVERSE and etc)

6. If the deviation is applicable, determine possible causes and note any protective systems.

7. Evaluate the consequences of the deviation (if any).

8. Recommend action: what, by whom, by when.

9. Record all information.

10. Repeat steps 5 through 9 until all applicable guide words have been applied to the chosen process parameter.

11. Repeat steps 4 through 10 until all applicable process parameters have been considered for the given study node.

12. Repeat steps 2 through 11 until all study nodes have been considered for the given

section and proceed to the next section on the flow sheet.