HAZOP_GUIDE_BRITISH_STANDARD_IEC_61882_2001

In particular the use of computer packages to replace

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Unformatted text preview: e to generating deviations by applying guide words directly to elements (and, if necessary, characteristics). Whilst these packages will identify many hazards and produce a print-out which resembles the print-out from a HAZOP they lack the rigour of generating hazards from the “work system” and have limited applicability beyond the area of continuous process units. In particular, the use of computer packages to replace the study leader entirely is to be discouraged. The random application of ad hoc checklists cannot be regarded as a HAZOP as defined in this standard. A.3 HAZOP study report A final report of the HAZOP study should be prepared and contain the following: · s ummary; · c onclusions; · s cope and objectives; · o utput of the study itemized as outlined in 6.6.3; · H AZOP worksheets; · l isting of drawings and documentation used in the study; · r eferences to previous studies, data bases, etc. that were used in the course of the study. © BSI ISB © 1002−80 August 1002−8028ISB © 2001 27 72 72 BS IEC 61882:2001 6 1882 Ó I EC:2001 – 29 – Annex B (informative) Licensed Copy: Puan Ms. Norhayati, Petroliam Nasional Berhad 4397000, 01 October 2003, Uncontrolled Copy, (c) BSI Examples of HAZOP The purpose of the examples contained in this annex is to illustrate how the principles of HAZOP examination, outlined in the guide (particularly in 4.2, 6.4 and 6.5) are applied to a range of applications encompassing various industries and activities. It should be noted however that the examples have been simplified significantly for illustrative purposes and do not purport in any way to reproduce all the detailed technical complexity of real case studies. It should also be noted that only sample outputs are provided. B.1 Introductory example The purpose of this example is to introduce the reader to the basics of the HAZOP examination method. The example is adopted from one given in the original publication on HAZOP [1] 1. Consider a simple process plant, shown in Figure B.1. Materials A and B are continuously transferred by pump from their respective supply tanks to combine and form a product C in the reactor. Suppose that A always has to be in excess of B in the reactor to avoid an explosion hazard. A full design representation would include many other details such as the effect of pressure, reaction and reactant temperature, agitation, reaction time, compatibility of pumps A and B, etc. but for the purposes of this simple illustrative example they will be ignored. The part of the plant being examined is shown in bold. ——————— 1 28 82 82 T he figures in brackets refer to the Bibliography. © BSI 28 1002−80ISB © 1002−80 ISB August 2001 BS IEC 61882:2001 6 1882 Ó I EC:2001 – 30 – Licensed Copy: Puan Ms. Norhayati, Petroliam Nasional Berhad 4397000, 01 October 2003, Uncontrolled Copy, (c) BSI Vent Material A Reactor 10 Pump A Material B 10 Pump B Reaction: A + B = C Overflow Product C Component A must always be in excess of component B to avoid an explosion IEC 453/01 Figure B.1 – Simple flow sheet The part of the system selected for examination is the line from the supply tank holding A to the reactor, including pump A. The design intent for this part is to continuously transfer material A from the tank to the reactor at a rate greater than the transfer rate of material B. In terms of the elements suggested in 4.2, the design intent is given in the header: Material Activity Source Destination A Transfer (at a rate >B) Tank for A Reactor Each of the guide words indicated in Table 3 (plus any others agreed as appropriate during the preparatory work, see 6.4) is then applied to each of these elements in turn and the results recorded on HAZOP worksheets. Examples of possible HAZOP outputs for the “material” and “activity” elements are indicated in Table B.1, where the “by exception” style of reporting is utilized and only meaningful deviations are recorded. Having examined each of the guide words for each of the elements relevant to this part of the system, another part (say the transfer line for material B) would be selected and the process repeated. Eventually all parts of the system would be examined in this manner and the results recorded. © BSI ISB © 1002−80 August 1002−8028ISB © 2001 29 92 92 Licensed Copy: Puan Ms. Norhayati, Petroliam Nasional Berhad 4397000, 01 October 2003, Uncontrolled Copy, (c) BSI STUDY TITLE: P ROCESS EXAMPLE SHEET: 1 of 4 Drawing No.: REV. No.: DATE: D ecember 17, 1998 TEAM COMPOSITION: LB, DH, EK, NE, MG, JK MEETING DATE: D ecember 15, 1998 PART CONSIDERED: Transfer line from supply tank A to reactor DESIGN INTENT: Material: A Source: Tank for A No. 1 Guide word NO Element Material A Deviation No Material A Activity: T ransfer continuously at a rate greater than B Destination: 6 8812 E BS IEC 61882:2001 I2:C100 30 03 Table B.1 – E xample HAZOP worksheet for introductory example Reactor Possible causes Supply Tank A is empty Consequences No flow of A into reactor Safeguards Comments Actions required Action allocated to None shown Situation not acceptable Consider installation on tank A of a low-level alarm plus a low/low-level trip to stop pump B MG Explosion NO Transfer A (at a rate >B) No transfer of A takes place Pump A stopped, line blocked Explosion None shown Situation not acceptable Measurement of flow rate for material A plus a low flow alarm and a low flow which tr...
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