Safely HAZOP studies

For example, a traditional checklist is, by definition, based on the process experience the author accumulates from various sources. The checklist is likely to provide incomplete insights into the design, procedural, and operating features necessary for a safe process. The what-if part of the analysis uses a team s creativity and experience to brainstorm potential accident scenarios. However, because the what-if analysis method is usually not as detailed, systematic, or thorough as some of the more regimented approaches (e.g., HAZOP study, FMEA), use of a checklist permits the PrHA team to fill in any gaps in their thought process. 

An engineering evaluation should then be made of the worst-case consequences, with the goal that the plant will be safe even if the worst case occurs. A HAZOP study could be used to help accomplish worst-case thinking. When the process designers know what the worst-case conditions are, they should ... 

Ensuring safe operations and maintenance by Hazid and Hazop studies Compliance with statutory rules and regulations Procuring materials and machinery... 

The predetermined safe position of the process equipment device under control, as determined by operational experience, a preliminary hazards analysis, or formal Hazard and Operability (HAZOP) study. Unless otherwise specified, the safe-state is de-energized, i.e., without power, pneumatic, or hydraulic supply. It is also the state of the process after acting to remove the hazard resulting in no significant harm. 

The safety issues in MBS processing involve the presence of flammables and oxygen in the system together. Extensive hazard and operability (HAZOP) studies of MBS processes have been conducted to meet rigorous safety and environmental protection standards. The Huish MBS plant has been underwritten by factory mutual underwriters and already has more than 5 years of trouble-free operation the older Lion and Stepan plants have operated safely for longer periods. 

A well-conducted HAZOP study should eliminate 80-85% of the major hazards, thereby reducing the level of risk in the plant. In safety critical plant another HAZOP study, carried out when the detailed design has been finalised, could increase the probability of safe operations. 

A hazard and opeiabilily study (Hazop), is a standard hazard analysis technique used worldwide in the process industries in the preliminary safely assessment of new systems or modihcations to existing ones. The Hazop study is a detailed examination, by a group of specialists, of components within a system to determine what would happen if that component were to operate outside its normal design mode. Each ccmponent will have one or more parameters associated with its operation such as pressure, flow rate, or electrical power. The Hazop study looks at each parameter in turn and uses guide words to list the possible off-normal behaviour such as more , less , high , low , yes , or no . The effect of such behaviour is then assessed. 

When failure occurs, the simplest action is to stop or hold at the current operating state in response to any abnormal condition, and let the process operator determine the cause of the problem. However, some failures lead to hazardous conditions that require immediate action waiting for the operator to decide what to do is not acceptable. The appropriate response to such situations is best determined in conjunction with process hazards and operability (HAZOP) studies. For example, guidelines for safe operation of batch reaction systems have been published (Center for Chemical Process Safety, 1999). 

Technical and trade organi2ations are concerned with safety and the environment. The Chlorine Institute in North America and Euro Chlor in Western Europe are examples of organi2ations dedicated to the safe production, transport, and use of chlorine. Ha2ard and operabiHty studies (HAZOP) reviews for new designs, plants, and expansions (135) have become required by poHcy in many operating companies. Papers on safety and environmental subjects are given at most technical meetings (136—138). 

New systems or processes may also need to be qualified from an operational safety perspective. This is particularly relevant in the case of chemical synthesis involving exothermic reactions. Critical safety aspects are usually identified using hazard operability or HAZOP assessments and studies. For example, a HAZOP analysis of an exothermic reaction vessel would involve consideration of the consequence of failure of the motors for mixers or circulation pumps for cooling water. Thus, the qualification of such a system would involve checks and assessment to ensure that the system/process can be operated safely and that pressure relief valves or other emergency measures are adequate and functional. 

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