HAZOP_GUIDE_BRITISH_STANDARD_IEC_61882_2001

A the study leader starts by selecting a part of the

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Unformatted text preview: rd identification techniques such as HAZOP derive their power from a disciplined step by step examination process. There are two possible sequences of examination: “Element first” and “Guide word first”, as shown in Figures 2a and 2b respectively. The element first sequence is described below. a) The study leader starts by selecting a part of the design representation as a starting point and marking it. The design intent of the part is then explained and the relevant elements and any characteristics associated with these elements identified. b) The study leader chooses one of the elements and agrees with the team whether the guide word should be applied directly to the element itself or to individual characteristics of that element. The study leader identifies which guide word is to be applied first. c) The first applicable guide word interpretation is examined in the context of the element or characteristic being studied in order to see if there is a credible deviation from the design intent. If a credible deviation is identified, it is examined for possible causes and consequences. In some applications it is found useful to categorize the deviations either in terms of the potential severity of the consequences or in terms of a relative risk ranking based on the use of a risk matrix. The use of risk matrices is further discussed in IEC 60300-3-9. d) The team should identify the presence of protection, detection and indication mechanisms for the deviation, which may be included within the selected part or form a portion of the design intentions of other parts. The presence of such mechanisms should not stop the potential hazard or operability problem being explored or listed or attempts being made to reduce the probability of its occurrence or mitigating its consequences. e) The study leader should summarize the results that are documented by the recorder. Where there is a need for additional follow-up work, the name of the person responsible for ensuring that the work is carried out should also be recorded. f) The process is then repeated for any other interpretation for that guide word; then for another guide word; then for each characteristic of the element under examination (if analysis at the characteristic level has been agreed for that element); then for each element of the part under study. After a part has been fully examined, it should be marked as completed. The process is repeated until all parts have been analysed. An alternative method of guide word application to that described above, is to apply the first guide word to each of the elements within a part in turn. When this has been completed, the study proceeds with the next guide word which again is applied to all elements in turn. The process is repeated until all the guide words have been used for all the elements in that particular part before moving on to another part. (See Figure 2b.) The selection of which sequence to be followed in any particular study should be made by the study leader and his team. It is influenced by the detailed manner in which the HAZOP examination is conducted. Other factors involved in the decision include the nature of the technologies involved, the need for flexibility in the conduct of the examination and, to some extent, the training which the participants have received. 20 02 02 © BSI 28 1002−80ISB © 1002−80 ISB August 2001 BS IEC 61882:2001 6 1882 Ó I EC:2001 – 22 – Start Explain overall design Licensed Copy: Puan Ms. Norhayati, Petroliam Nasional Berhad 4397000, 01 October 2003, Uncontrolled Copy, (c) BSI Select a part Examine and agree design intent Identify relevant elements Identify whether any of the elements can be usefully sub-divided into characteristics Select an element (and characteristic if any) Select a guide word Apply the guide word to the selected elements (and to each of its characteristics as relevant) to obtain a specific interpretation Yes Is deviation credible? No No Investigate causes, consequences and protection or indication, and document Have all interpretations of the guide word and element/characteristics combinations been applied? Yes No Have all guide words been applied to the selected element? Yes Have all elements been examined? No Yes Have all parts been examined? No Yes Stop IEC 451/01 Figure 2a – Flow chart of the HAZOP examination procedure – Element first sequence © BSI ISB © 1002−80 August 1002−8028ISB © 2001 21 12 12 BS IEC 61882:2001 6 1882 Ó I EC:2001 – 23 – Start Explain overall design Licensed Copy: Puan Ms. Norhayati, Petroliam Nasional Berhad 4397000, 01 October 2003, Uncontrolled Copy, (c) BSI Select a part Examine and agree design intent Identify relevant elements Identify whether any of the elements can be usefully sub-divided into characteristics Select a guide word Select an element (and characteristic if any) Apply the guide word to the selected element (and to each of its characteristics as relevant) to obtain a specific interpretation Yes Is dev...
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