1、Criticality ClassificationGuideline for InstrumentationApproved 2 January 2003ISATR91.00.022003TECHNICAL REPORTISA The Instrumentation,Systems, andAutomation Society TMISA-TR91.00.02-2003Criticality Classification Guideline for InstrumentationISBN: 1-55617-841-7Copyright 2003 by ISA The Instrumentat
2、ion, Systems, and Automation Society. All rights reserved.Not for resale. Printed in the United States of America. No part of this publication may be reproduced,stored in a retrieval system, or transmitted in any form or by any means (electronic mechanical,photocopying, recording, or otherwise), wit
3、hout the prior written permission of the Publisher.ISA67 Alexander DriveP.O. Box 12277Research Triangle Park, North Carolina 27709- 3 - ISA-TR91.00.02-2003PrefaceThis preface, as well as all footnotes and annexes, is included for information purposes and is not part ofISA-TR91.00.02-2003.This docume
4、nt has been prepared as part of the service of ISAThe Instrumentation, Systems, andAutomation Societytoward a goal of uniformity in the field of instrumentation. To be of real value, thisdocument should not be static but should be subject to periodic review. Toward this end, the Societywelcomes all
5、comments and criticisms and asks that they be addressed to the Secretary, Standards andPractices Board; ISA; 67 Alexander Drive; P. O. Box 12277; Research Triangle Park, NC 27709;Telephone (919) 549-8411; Fax (919) 549-8288; E-mail: standardsisa.org.The ISA Standards and Practices Department is awar
6、e of the growing need for attention to the metricsystem of units in general, and the International System of Units (SI) in particular, in the preparation ofinstrumentation standards. The Department is further aware of the benefits to USA users of ISAstandards of incorporating suitable references to
7、the SI (and the metric system) in their business andprofessional dealings with other countries. Toward this end, this Department will endeavor to introduceSI-acceptable metric units in all new and revised standards, recommended practices, and technicalreports to the greatest extent possible. Standar
8、d for Use of the International System of Units (SI): TheModern Metric System, published by the American Society for Testing see flowchart A1. Flow chart A1 provides an overview of key considerations when developing an operating facilityclassification scheme. The flow chart should be modified for spe
9、cific applications. The flow chart stressesthe development of an overall plan (e.g., Figure 5) prior to addressing the details of a specificclassification category (e.g., Table A1). The order shown for the classification categories may be modifiedto meet application needs. Note that some categories
10、may not exist depending on the application.3.2 Annex A, Table A1 reflects an asset-related classification breakdown example.3.3 Annex A, Table A2 reflects a criticality classification example developed in response to U.S. OSHAregulation 29 CFR 1910/119. Further detail is provided in Annex B.3.4 Anne
11、x A, Figure A1 combines Tables A1 and A2 into a typical operating facility processinstrumentation criticality classification example.NOTE “SIL” is an acronym for Safety Integrity Level. SIL is defined as one of three possible integrity levels (SIL1,SIL2, SIL3) of safety instrumented functions. SILs
12、are defined in terms of probability of failure on demand (PFD) (seeAnnex B, Table B1). It should be noted that presently the international community (see clauses 6.3 and 6.4)recognizes four SILs (SIL 1, SIL 2, SIL 3, SIL 4), while ANSI/ISA-84.01-1996 recognizes only three SILs.3.5 Annex C provides a
13、n example of criticality ranking.4 Additional considerations4.1 Good engineering practices are required regardless of the criticality classification.4.2 Often a system that belongs in one classification is utilized in another classification. One exampleis that of a single burner boiler installed in
14、a process line. A single burner boiler falls under NFPA 85.However, when installed in a process that falls under U.S. OSHA 29 CFR Part 1910.119, a boilersinstrumentation should be designed, operated, and maintained per ANSI/ISA-84.01-1996 as well asNFPA 85. Therefore, an instrument engineer may rank
15、 the furnace instrumentation also against bothNFPA 85 and ANSI/ISA-84.01-1996.4.3 It is common for instrumentation associated with machinery located in a process to be designedaccording to EN 954 (see Annex A, Table A3) and ANSI/ISA-84.01-1996 (see Annex A, Table A2).4.4 Annex A, Table A3 lists vari
16、ous process and machinery functional safety standards and some oftheir associated criticality classifications.ISA-TR91.00.02-2003 - 14 -5 AbbreviationsACR Asset Criticality RankingAK Application Klass (class)BPCS Basic Process Control SystemRC Risk Klass (class)SECR Safety Identification of Emergenc
17、y Shutdown Systems and Controls That AreCritical to Maintaining Safety in Process Industries.6.6 U.S. Department of Labor, Occupational Safety and Health Administration (OSHA), FederalRegulation 29 CFR Part 1910; Process Safety Management of Highly Hazardous Chemicals; Explosivesand Blasting Agents;
18、 Final Rule, 1992.6.7 European Committee for Standardization (CEN) EN 954-1, Safety of Machinery - Safety-RelatedParts of Control Systems - Part 1: General Principles for Design.6.8 Deutsches Institut fur Normung (DIN), DIN V 19250, Control technology; fundamental safetyaspects to be considered for
19、measurement and control equipment6.9 Deutsches Institut fur Normung (DIN), VDI/VDE 2180 Blatt 2, Safeguarding of industrial processplants by means of process control engineering - Classification of process control systems - Realisation,operation and testing of safety instrumented systems.6.10 Americ
20、an Institute of Chemical Engineers (AIChE), Guidelines for Safe Automation of ChemicalProcesses, 1993; AIChE, 345 East 47th Street, New York, NY 10017, Tel: (212) 705-7657,www.aiche.org.6.11 CEN/TC 114/WG 6 - N 860 - prEN ISO 13849-1 (EN 954-1 Rev. 12): Safety of machinery - Safety-related parts of
21、control systems - Part 1: General principles for design. Descriptors: safety of machines,control devices, design, interfaces, hazards, generalities, defects, verification.6.12 STSARCES, Standards for Safety-Related Complex Electronic Systems, Annex 11, Applicability ofIEC 61508 the STSARCES report,
22、including the annex, is available for download at:http:/www.safetynet.de/EC-Projects/stsarces/STSARCESMain.htm.This page intentionally left blank.- 17 - ISA-TR91.00.02-2003Annex A GuidanceExample criticality classification flow chart A1 (see Clause 3.1)Note: This flow chartcould be used for non-proc
23、ess sector facilities.Yes NoIs the facility a process sector operating facility?Is it an existing or new facility?Verify that the existing criticalityclassification chart covers the necessaryissues (see Table A3)Safety critical Asset criticalDevelop or modify anoperating facility criticalityclassifi
24、cation chart (see Fig. 1,2, 3, 4, however, components of the IEC 61508 development life cycle requirements and the quantitative evaluationof hardware may not exist in the AK rating.Figure B3 Risk graph DIN V 19250/NE31/IEC 61511 (see Clause B.6)- -432Risk Area(low Risk)Cannot be coveredby SIF onlyS2
25、S3S4A1A2A1A2G1G2G1G2S1no safety system requirementsno special safety requirementsW3 W2 W112 -32543654765876Risk Area(highRisk)DIN V 19250 VDI/VDE 2180IEC61511SIL 1SIL 2SIL 3SIL 4A SIF is notsufficient11Note: See Figure B2 for legend.- 25 - ISA-TR91.00.02-2003Annex C Criticality rankings exampleThis
26、annex provides an example procedure a facility may use to develop criticality rankings for itsinstrumentation.C.1 After defining the Instrumentation Categories for the operating facility, one can now determine theCriticality Rankings for each instrumentation system and establish any facility specifi
27、c requirements for eachranking group.C.2 It is the responsibility of each operating facility to determine the number of Critical Ranking groups. Itis recommended that a minimum of three critical ranking groups be defined. One may define additionalcritical ranking categories as appropriate.C.3 Each I
28、nstrument System is then categorized under one of the critical ranking groups established. Allinstrumentation systems that fall into one of the defined instrumentation categories should be assigned toone of the criticality ranking groups (which may include a “nonclassified” category).C.4 Once all th
29、e instrumentation systems are assigned to a Critical Ranking group, one may establishspecific requirements for the Critical Ranking, or for specific instrumentation systems within a critical ranking.Requirements may include one or more of the following:C.4.1 Purchasing/Procurement requirementsC.4.2
30、Supplier requirementsC.4.3 Special inspection or acceptance test requirementsC.4.4 OtherThe above requirements are examples only. Many other requirements may be specified depending on theapplication.ISA-TR91.00.02-2003 - 26 -C.5 ExampleC.5.1 Assume the process facility establishes Instrumentation Sy
31、stem Categories as shown in Clause 2,Figure 5.C.5.2 Figure C1 shows a possible criticality ranking scheme. For this example, we identified four CriticalRanking Categories.NOTE The operating facility chose to alter the ranking provided in the guidelines to suit its application.C.5.2.1 Critical Rankin
32、g Category #4 consisted of the OSHA PSM/EPA RMP regulated SafetyInstrumented Systems and systems identified as Major Asset.C.5.2.2 Critical Ranking Category #3 consisted of all other Safety Instrumented Systems (OSHA & EPAgen. duty clauses).C.5.2.3 Critical Ranking Category #2 consisted of the remai
33、nder of the Asset Systems.C.5.2.4 Critical Ranking #1 consisted of all other instrumented systems in the process facility.Figure C1 Developing criticality rankings from guidance demoNow that a Criticality Ranking represents each instrument system, specific requirements can now beestablished. Referen
34、ces are available to assist you in determining any facility-specific requirements (seeTable C1).Criticality Ranking #4- Safety & Environmental per OSHA PSM/EPARMP regulations- Major AssetsCriticality Ranking #3- Other Safety (OSHA & EPA gen. duty clauses)Criticality Ranking #2- Non Critical AssetsCr
35、iticality Ranking #1- Non Classified- 27 - ISA-TR91.00.02-2003Table C.1 Example of facility-specific requirementsCriticality Ranking Description Process Facility Requirements ReferencesCR #4 OSHA PSM/EPARMPAsset CriticalSafety & Environmental- Prior Use- Designed per IEC 61508Sect 2/3Asset Critical-
36、 See Note C.1Safety/EnvironIEC 61511ANSI/ISA-84.01AssetSee Annex ACR #3 SafetyInstrumentedSystems for OSHA& EPA gen. duty cl.Safety & Environmental- Prior Use- Designed per IEC 61508 Sect 2/3Safety/EnvironIEC 61511ANSI/ISA 84.01CR #2 Minor Assets Asset Critical- See standard operating facilityAssetS
37、ee Annex BCR #1 Nonclassified No Specific RequirementsFollow standard operating facilityprocurement processesOperating facilitystandardNOTE C.1: Asset Critical RequirementsIt is the responsibility of the operating facility to determine the requirements for instrumentation systems deemed “AssetCritic
38、al.” These requirements may include the following:- Prior use in similar environments- A specific number of years of experience using the instrument- Designed per IEC 61508 Sections 2 and 3- Special tests or documentation to be supplied by the supplier- Other- Supplier is on qualified supplier list-
39、 Supplier has approved quality system/program (e.g., ISO 9001:2000)This page intentionally left blank.Developing and promulgating sound consensus standards, recommended practices, and technicalreports is one of ISAs primary goals. To achieve this goal the Standards and Practices Departmentrelies on
40、the technical expertise and efforts of volunteer committee members, chairmen and reviewers.ISA is an American National Standards Institute (ANSI) accredited organization. ISA administers UnitedStates Technical Advisory Groups (USTAGs) and provides secretariat support for InternationalElectrotechnica
41、l Commission (IEC) and International Organization for Standardization (ISO) committeesthat develop process measurement and control standards. To obtain additional information on theSocietys standards program, please write:ISAAttn: Standards Department67 Alexander DriveP.O. Box 12277Research Triangle Park, NC 27709ISBN: 1-55617-841-7
