HAZOP AND WHAT-IF REVIEW PROCEDURES

Three areas of preparation are needed for a review to take place - the location, administrative support, and documentation. 

The location of where a review is held should be determined by where the most amount of information and personnel knowledgeable in the facility design and operation are located. Typically new designs will be have the data at the engineering contractor s offices and the reviews will be held there. For existing facilities, the review is usually held at the facility itself. 

If the review is conducted overseas, two main issues may arise. Firstly, the local language may be inconsistent with available specific safety review software or a consultant, if used, may not be available in the host country language. A translator is sometimes used in these instances. Secondly, if a portable personal computer is used, its power requirements may be different both in voltages and plug connections. In these circumstances it is best to plan ahead and bring power converters, adapters and multiple outlet busbars. 

Lunch and refreshments should be provided to the review meeting room to avoid disruption and maintain continuity of personnel attendance. Further discussion of issues may also be informally pursued over lunch and breaks. 

Interruptions from messages, telephone, or other enquiries should be kept to an absolute minimum during the review sessions. If possible the conference room should be posted with a Conference In Session, Do Not Disturb sign. 

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HAZOP and What-If Review Procedures 47 regardless of the specified failure position of the valve. 

HAZOP and What-If reviews are a basically a communication exercise. Information is presented, discussed, analyzed and recorded. Specifically the safety aspects are identified, to determine if adequate design measures have be taken to prevent major accidents. Communication and evaluation are the prime facets of the procedures. 

The reader is reminded that a HAZOP or What-If report is a living document for a facility. As changes are made to a facility or its procedures the HAZOP or What-If review(s) will be updated to represent the current facility. Process hazard analysis reviews are also required to be updated and revalidated every five years as a minimum by U.S. regulations (OSHA and EPA). 

The safety impact of design and construction changes to a project performed after the final HAZOP or What-If reviews and prior to commissioning are identified as part of the facility Pre-Startup-Safety-Review (PSSR) and Management of Change (MOC) procedures. 

Most hazard identification procedures have the capabiUty of providing information related to the scenario. This includes the safety review, what-if analysis, hazard and operabiUty studies (HAZOP), failure modes and effects analysis (FMEA), and fault tree analysis. Using these procedures is the best approach to identifying these scenarios. 

Several qualitative approaches can be used to identify hazardous reaction scenarios, including process hazard analysis, checklists, chemical interaction matrices, and an experience-based review. CCPS (1995a p. 176) describes nine hazard evaluation procedures that can be used to identify hazardous reaction scenarios-checklists, Dow fire and explosion indices, preliminary hazard analysis, what-if analysis, failure modes and effects analysis (FMEA), HAZOP study, fault tree analysis, human error analysis, and quantitative risk analysis. 

A HAZOP is performed on all new chemicals following process review, preliminary equipment review, and development of preliminary standard operating procedures (SOP). What-if and checklists are typically used to review a process without process design and chemistry changes. 

There are various types of analyses that are used for a process hazard analysis (PHA) of the equipment design and test procedures, including the effects of human error. Qualitative methods include checklists, What-If, and Hazard and Operability (HAZOP) studies. Quantitative methods include Event Trees, Fault Trees, and Failure Modes and Effect Analysis (FMEA). All of these methods require rigorous documentation and implementation to ensure that all potential safety problems are identified and the associated recommendations are addressed. The review should also consider what personal protective equipment (PPE) is needed to protect workers from injuries. 

First, the importance of learning lessons from past process safety incidents is highlighted in Section 3.2. The subsequent section presents preliminary hazard review procedure, risk matrix, what-if method, plot plan and layout review, pressure relief system review and fire safety design aspects. Section 3.4 presents PHA techniques and procedures hazards and operability analysis (HAZOP), failure modes and effects analysis (FMEA), instrumented protective system (IPS) design, fault trees, event trees, layer of protection analysis (LOPA) and finally SIS life eyele. The importanee of revision of PSI is highlighted in Seetion 3.5. 

Risk assessment represents a careful analysis of the premises, processes and work activities to identify what could cause harm to people to enable decisions to be made as to whether sufficient precautions have aheady been taken or whether further controls are needed. The aim of Risk Assessment it to individualize a risk priority that allows to define a hierarchy of intervention activities (design review, procedures, formation and information) needed to eliminate or reduce the risk. There are many methods for Risk Assessment (FMEA, FTA, HAZOP, What-if, MOZAR, etc.) (Hiromitsu 1996) that are all usable. 

To develop the risk-management strategy, start with a process hazards analysis (PHA) and review the process design and its control, operation, and maintenance practices. Select a multidisciplinary team with expertise in these areas, and use an accepted hazard-evaluation procedure, such as a hazard and operability (HAZOP), what-if, or checklist analysis, to determine how process deviations from intended... 

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