The conformance of elements or characteristics to

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Unformatted text preview: e system function of each part and element in a qualitative or quantitative manner. It should also describe the interactions of the system with other systems, with its operator/user and possibly with the environment. The conformance of elements or characteristics to their design intent determines the correctness of operations and in some cases the safety of the system. The representation of the system consists of two basic parts: · t he system requirements; · a p hysical and/or logical description of the design. © BSI ISB © 1002−80 August 1002−8028ISB © 2001 11 11 BS IEC 61882:2001 6 1882 Ó I EC:2001 – 13 – The resulting value of a HAZOP study depends on the completeness, adequacy and accuracy of the design representation including the design intent. Care should be taken, therefore, in preparation of the information package. If HAZOP is being conducted in the operational or disposal phase, care should be taken to ensure that any modifications are reflected in the design representation. Before starting the examination, the team should review this information package, and if necessary have it revised. Licensed Copy: Puan Ms. Norhayati, Petroliam Nasional Berhad 4397000, 01 October 2003, Uncontrolled Copy, (c) BSI 4.3.2 Design requirements and design intent The design requirements consist of qualitative and quantitative requirements which the system has to satisfy, and provide the basis for development of system design and design intent. All reasonable use and misuse conditions which are expected by the user should be identified. Both the design requirements and resulting design intent have to meet customer expectations. On the basis of system requirements a designer develops the system design, i.e. a system configuration is arrived at, and specific functions are assigned to subsystems and components. Components are specified and selected. The designer should not only consider what the equipment should do, but also ensure that it will not fail under any unusual set of conditions, or that it will not wear out during the specified lifetime. Undesirable behaviour or features should also be identified so they can be designed out, or their effects minimized by appropriate design. The above information provides the basis for identifying the design intent for the parts to be examined. The “design intent “ forms a baseline for the examination and should be correct and complete, as far as possible. The verification of design intent (see IEC 61160), is outside of the scope of the HAZOP study, but the study leader should ascertain that it is correct and complete to allow the study to proceed. In general most documented design intents are limited to basic system functions and parameters under normal operating conditions. However provisions for abnormal operating conditions and undesirable activities which may occur (e.g. severe vibrations, water hammer in pipes, voltage surges which may lead to failure) are rarely mentioned, but should be identified and considered during the examination. Also deterioration mechanisms such as ageing, corrosion and erosion and other mechanisms which cause deterioration in material properties are not specifically stated. However they have to be identified and considered in a study using appropriate guide words. Expected life, reliability, maintainability and maintenance support should also be identified and considered together with hazards which may be encountered during maintenance activities, provided they are included in the scope of the HAZOP study. 5 5.1 Applications of HAZOP General Originally HAZOP was a technique developed for systems involving the treatment of a fluid medium or other material flow in the process industries. However its area of application has steadily widened in recent years and for example includes usage for: · 12 21 21 s oftware applications including programmable electronic systems; © BSI 28 1002−80ISB © 1002−80 ISB August 2001 BS IEC 61882:2001 6 1882 Ó I EC:2001 – 14 – s ystems involving the movement of people by transport modes such as road and rail; · e xamining different operating sequences and procedures; · a ssessing administrative procedures in different industries; · Licensed Copy: Puan Ms. Norhayati, Petroliam Nasional Berhad 4397000, 01 October 2003, Uncontrolled Copy, (c) BSI · a ssessing specific systems, e.g. medical devices. HAZOP is particularly useful for identifying weaknesses in systems (existing or proposed) involving the flow of materials, people or data, or a number of events or activities in a planned sequence or the procedures controlling such a sequence. As well as being a valuable tool in the design and development of new systems, HAZOP may also be profitably employed to examine hazards and potential problems associated with different operating states of a given system, e.g. start-up, standby, normal operation, normal shutdown, emergency shutdown. It can also be employed for batch and unsteady-state processes and sequences as well as for continuous ones. HAZOP may be viewed as an integral part of the overall process of value e...
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This note was uploaded on 09/15/2011 for the course ECON 102 taught by Professor Calvin during the Winter '11 term at Oxford Brookes.

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