HAZOP method

Process Hazards Analysis. Analysis of processes for unrecogni2ed or inadequately controUed ha2ards (see Hazard analysis and risk assessment) is required by OSHA (36). The principal methods of analysis, in an approximate ascending order of intensity, are what-if checklist failure modes and effects ha2ard and operabiHty (HAZOP) and fault-tree analysis. Other complementary methods include human error prediction and cost/benefit analysis. The HAZOP method is the most popular as of 1995 because it can be used to identify ha2ards, pinpoint their causes and consequences, and disclose the need for protective systems. Fault-tree analysis is the method to be used if a quantitative evaluation of operational safety is needed to justify the implementation of process improvements. 

The overall HAZOP method is suimmu ized in the following steps ... 

The HAZOP Study is a very popular predictive method which was developed in the Mond Division of Imperial Chemical Industries during the 1960s. A HAZOP (Hazard and Operability) study is an analysis method for identifying hazards and problems which prevent efficient operation. Trevor Kletz was an early promoter of the HAZOP Method and in one of his recent books [18], he states ... 

Robert Johnson presented a technical paper in April 1992 entitled HAZOPS Today [19] in which he stated, The hazard and operability studies (HAZOPS) method has likely become, over a period of less than ten years, the most widely-used hazard evaluation procedure in the process industries. Johnson also explained that HAZOPS is a relative latecomer to the United States and it has attained a high degree of prominence in the U.S. process industries. The method began in the United Kingdom and has now spread throughout western Europe and North America. (See Figure 11—1.)... 

Simultaneously most petroleum and chemical companies have also brainstormed a safety review which asks "What-If" questions of the process (e.g. SOHIO ca. 1967). This is common practice in the industry and during design phases of a facility but was usually verbal and less formal in its application. Therefore not as much historical documentation is available on it, as compared to the HAZOP method. 

It has been found that the What-If style of process hazard analysis is a convenient method to use for a "simple" facility. For simple facilities, the detailed HAZOP approach has been found to be tedious and just as productive as a What-If method. The What-If approach stimulates generation of new ideas and discussion to cover issues associated with the items under review, as well as addressing generic issues. The specific HAZOP review is not necessary when the process is simple and well understood by the reviewing team. The team can readily review the major items of concern by asking What-If questions such as what happens when a pump fails, without relying on itemized and detailed variations of a process condition by the HAZOP method, such as high level, low pressure, etc. 

Processes that contain unusual, complicated or extremely hazardous materials should be reviewed by the detailed HAZOP method to ensure major possible events have been accounted for which may not be familiar to the team. This may also be true when a high employee or public population may be exposed to potential hazards (such as may be the case with some offshore oil production facilities). 

If doubt exist as to what method to apply, the HAZOP method should be chosen over the What-If method. The What-If approach relies on the team leader to ferret out the real hazards associated with the process. The systematic HAZOP approach will examine each portion of the system to determine hazardous conditions. 

The standard lists six different methods for conducting a hazards analysis. It also provides for the use of other methods that are not hsted in the regulation. The key point is that the regulation permits a great deal of flexibility regarding the choice of method. In particular, there is no requirement that the HAZOP method always be used. The onus is on the facility s management to choose the techniques that most effectively reduce risk. 

The first group of hazards analysis techniques covers those that are creative and that encourage out of the box or off the wall thinking. The What-If and HAZOP methods fall into the creative/imaginative category. 

As a result of its widespread use and acceptance, large numbers of people are now trained in the use of the HAZOP method, and many of those are also trained as leaders/facilitators. Furthermore, a HAZOP infrastructure has developed. Many consulting companies offer HAZOP facilitation services other companies provide special-purpose software. 

The HAZOP method is probably the most thorough hazards analysis technique, and the one which has the largest number of experienced users and trained leaders. Therefore, it is likely to the method which offers the greatest assurance that major hazards have been identified. 

The checklist approach is generally part of other hazards analysis techniques. The HAZOP method itself is a form of checklist, and FMEAs use a set of checklist questions. 

May be said that is a mistake call HazOp a safety assessment tool, since it is much more than that. Because of its method, HazOp goes beyond risks and process deviations to maintenance and quality as well. The HazOp method is, in short terms ... 

Hazard analysis aetivities have been performed for some time by the Trust. The added value of reeent improvements has been to provide a formal framework and associated methods into which they fit as a major component. The analyses were founded on traditional risk management techniques. These have been reviewed and developed, resulting in a similar format for the records produced. Improvements have been made by using a team rather than an individual for carrying out the analysis. The use of a set of guide words has helped to enable a consistent approach to the examination of design representations of the system under review. The technique was heavily based on the HAZOP method advocated in Def Stan 00-58 (MoD 1986) in this, it evolved into a similar form to that promoted as SHARD (Pumfrey 1999). 

Dr. AA, Hazard and Operability (HAZOP) Study http //www.cheme.utm.my/staff/arshad/ images/lecture/Safety/hazop method.ppt. 

The HAZOP method is widely used over the past 30 years becoming a reference when applied to petrochemical industries, specially after lEC 61882 2001 publication. The word HAZOP arises from the junction of the first 3 letters of word Hazard and the first 2 letters of the word Operability. 

By applying the HAZOP method at this Facility, based on the lEC 61882 2001 regulation, it is expected to achieve a higher level of safety ensuring a safer operation of the entire plant. 

Although not mandatory in the HAZOP method, this study comprised a risk assessment to all deviations detected. Risk assessment was performed through the use of a risk matrix already used in similar industries which included the combination of probability (possibility that the event occurs) and severity (as a consequence of the event). For the risk assessment criteria, four levels of probability were defined very unlikely/remote, likely/possible, probable and frequent. For severity were defined also four levels reduced, moderate, high, very high/catastrophic. The designation of risk parameters took into account the probability of occurrence, the measures implemented, historical events, potential injury to persons, to materials, to the environment. The combination between the four levels lead to four types of risk, grouped in two levels, acceptable/not significant, which even... 

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