ISA TR12 13 03-2009 Guide for Combustible Gas Detection as a Method of Protection《做为防护方法的可燃气体探测指南》.pdf

1、 TECHNICAL REPORT ANSI/ISA-TR12.13.03-2009 ANSI Technical Report prepared by ISA Guide for Combustible Gas Detection as a Method of Protection Approved 14 December 2009 ANSI/ISA-TR12.13.03-2009, Guide for Combustible Gas Detection as a Method of Protection ISBN: 978-1-936007-32-5 Copyright 2009 by t

2、he International Society of Automation. 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)

3、, without the prior written permission of the Publisher. ISA 67 Alexander Drive P.O. Box 12277 Research Triangle Park, North Carolina 27709 - 3 - ANSI/ISA-TR12.13.03-2009 Preface This preface, as well as all footnotes and annexes, is included for information purposes and is not part of ANSI/ISA-TR12

4、.13.03. This document has been prepared as part of the service of the International Society of Automation (ISA) toward a goal of uniformity in the field of instrumentation. To be of real value, this document should not be static but should be subject to periodic review. Toward this end, the Society

5、welcomes all comments and criticisms and asks that they be addressed to the Secretary, Standards and Practices 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 De

6、partment is aware of the growing need for attention to the metric system of units in general, and the International System of Units (SI) in particular, in the preparation of instrumentation standards. The Department is further aware of the benefits to USA users of ISA standards of incorporating suit

7、able references to the SI (and the metric system) in their business and professional dealings with other countries. Toward this end, this Department will endeavor to introduce SI-acceptable metric units in all new and revised standards, recommended practices, and technical reports to the greatest ex

8、tent possible. Standard for Use of the International System of Units (SI): The Modern Metric System, published by the American Society for Testing ISA; 67 Alexander Drive; P. O. Box 12277; Research Triangle Park, NC 27709. The primary reason for development of this technical report is to support the

9、 existing allowance for combustible gas detectors as a method of protection as permitted within ANSI/NFPA 70, National Electrical Code (NEC), Articles 500 and 505. This document also provides guidance on the use of combustible gas detectors as a method of area classification designation, gas free wo

10、rk permit (hot work permit) application and supplemental protection. Abstract This document provides guidance on the use of combustible gas detection as a method of protection as permitted by ANSI/NFPA 70 (NEC), the use of combustible gas detection for reduction of area designation by API 500 and AP

11、I 505, and to support the Hot Work Permit discussed in OSHA regulations 29 CFR 1910.119(k). Keywords Apparatus, combustible gas detection, fixed apparatus, combustible gas, combustible vapor, gas concentration, gas free work permit, hot work permit, portable apparatus, transportable apparatus This p

12、age intentionally left blank. - 11 - ANSI/ISA-TR12.13.03-2009 Introduction Combustible gas detection apparatus and systems should be used whenever there is the possibility of a hazard to life or property caused by the accumulation of a combustible gaseous atmosphere. Such apparatus can provide a mea

13、ns of reducing the hazard by detecting the presence of the combustible gas and issuing suitable audible or visual warnings and/or to initiate specific actions such as increased ventilation rates, plant shutdown, evacuation, and operation of fire suppression procedures. Combustible gas detection appa

14、ratus and systems may be used to monitor a gas atmosphere to initiate maintenance or operation action when low levels of combustible gas are detected. Additionally, combustible gas detection apparatus can be used to confirm that the area is suitable for engagement of work activities or to permit ene

15、rgizing electrical equipment in hazardous (classified) locations. Performance requirements for combustible gas detecting apparatus are set out in ANSI/ISA-12.13.01 (IEC 61779-1 to -5 Mod) and ANSI/FM 6325/ISA-12.13.04. This page intentionally left blank. - 13 - ANSI/ISA-TR12.13.03-2009 1 Scope Combu

16、stible gas detection used for process safety management may also be used to provide protection from explosion or fires by minimizing the possibility of an accumulation of combustible gases reaching ignitable levels. Criteria are developed to establish combustible gas levels to initiate alarms, initi

17、ate increase in ventilation rates and to initiate shutdown of processes to shutoff the flow of combustible gas that has breached containment. It is the intent of this document to compile and refine techniques for the use of combustible gas sensors and controllers to monitor and control sources of co

18、mbustible gas release into the atmosphere within designated spaces. It is also the intent that these products and techniques be adapted by industries and used with processes that have historically not employed combustible gas detection as a method of protection. 1.1 This document provides guidance o

19、n the use of a combustible gas detection system as a method of protection in Class I hazardous (classified) locations as defined within the following specific documents: ANSI/NFPA 70 (NEC) where for specific applications, electrical equipment that would not otherwise be permitted in the hazardous (c

20、lassified) location may be used in conjunction with combustible gas detection equipment; API RP 500 and API RP 505 for the use of combustible gas detection equipment to augment ventilation to ensure adequate dilution of combustible gas to prevent the possibility of ignition; Title 29 Code of Federal

21、 Regulations 1910.119(k) OSHA regulations to support the hot work permit. NOTE 1 Applicable combustible gas detection equipment performance standards include ANSI/ISA-12.13.01 and ANSI/FM 6325/ISA-12.13.04. For the purpose of this document combustible gases include combustible and flammable gases an

22、d vapors. Documents other than API RP 500 and RP 505 that describe area classification techniques, but which have not included combustible gas detection as part of the process to reduce the probability of ignition are ANSI/NFPA 497 and ANSI/ISA-TR12.24.01 (IEC 60079-10 Mod). Application of combustib

23、le gas detection and control as described in this document can provide additional protection from fire and explosion over typical area classification protection techniques by risk reduction methods. Industries that use these and other area classification documents can benefit by application of the t

24、echniques and criteria presented in this document. NOTE 2 Where mandatory text is provided in this Technical Report, the basis of the mandatory text is derived directly from referenced standards. 1.2 This document provides guidance on the use of portable combustible gas detection apparatus to allow

25、live maintenance on equipment or work with electrical powered tools within hazardous (classified) locations. 1.3 This document provides guidance on the use of combustible gas detection as a supplement in adequately ventilated spaces. 1.4 For the purpose of this document, apparatus includes fixed app

26、aratus; portable apparatus; and transportable apparatus. ANSI/ISA-TR12.13.03-2009 - 14 - 1.5 This document is NOT intended to cover the following: a) Guidance on area classification b) Apparatus intended only for the detection of non-combustible toxic gases c) Apparatus of laboratory or scientific t

27、ype intended only for analysis or measurement purposes d) Apparatus intended for mining applications e) Apparatus intended for applications in explosives processing and manufacture f) Apparatus intended only for process control applications g) Apparatus intended for the detection of a potentially co

28、mbustible atmosphere resulting from dust or mist in air h) Appartus intended for confined space entry. 1.6 Combustible gas hardware as described in this document may be applied as stand alone sensor/controllers or may be incorporated with or into another system such as, Basic Process and Control Sys

29、tem (BPCS), Safety Instrumented System (SIS) or Fire and Gas System that may be employed in an industrial facility. When ventilation rates must be controlled by the various responses of the combustible gas detection and control devices, there must also be interaction with the HVAC control system or

30、devices. 2 References The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ANSI/ISA-60079-0 (12.00.01)

31、, Electrical Apparatus for Use in Class I, Zones 0, 1 - has restricted public access; and - is governed by conditions of maintenance and supervision that ensure only qualified persons service the installation. b) The combustible gas detection equipment should be Listed for compliance to ANSI/ISA-12.

32、13.01 or ANSI/FM 6325/ISA-12.13.04. The combustible gas detectors are of a stationary type, permanently mounted and Listed for detection of the specific combustible gas to be encountered. - 17 - ANSI/ISA-TR12.13.03-2009 (1) The portion of the gas detection equipment installed in the described cases

33、of Clause 4 (a) (c) is required to be rated for Class I, Division 1/Zone 1, and that portion of the gas detection equipment outside the described cases is required to be rated for the location in which it is installed. (2) The power circuit for the combustible gas detection equipment is required to

34、be independent from any power circuit for the equipment within the space in order to permit continued gas detection monitoring by the gas detection system. NOTE 1 Reference ANSI/ISA-84.00.01 for information regarding safety instrumented system requirements and ANSI/NFPA 72 for information regarding

35、fire alarm code requirements. NOTE 2 Combustible gas detection equipment identified as “Classified as gas or vapor detection enclosures” or “Classified as gas or vapor detection equipment” does not meet the requirement in (b) above and should not be used in the applications reviewed in this guide. c

36、) An adequate number of sensors is installed and appropriately placed to ensure the sensing of combustible gas in the space protected in all areas where such gas might flow or accumulate. d) Sensing a combustible gas concentration of less than or equal to 20% LFL (as defined by risk assessment), or

37、1 LFLm, should activate a low level alarm (audible or visual, or both, as most appropriate for the location). NOTE 1 Reference ANSI/NFPA 72 for audible and visual alarm device details. NOTE 2 The 20% LFL has been historically acceptable to account for gas detection equipment accuracy considerations

38、for compliance with 49CFR 192.736. NOTE 3 OSHA 1910.146 Permit required confined entry spaces defines a hazardous atmosphere with “flammable gas, vapour, or mist in excess of 10 percent of its lower flammable limit (LFL)”. NOTE 4 ISO 21798 Gas Turbine Applications-Safety, Clause 5.19.4, specifies an

39、 alarm level of 10% LFL within ventilated turbine enclosures. Lower LFL alarm levels are recommended where dilution of gas concentrations are likely. e) Action to reduce the rate of increase in combustible gas concentration should be taken at or before the 20% LFL or 1 LFLm. NOTE The 20% LFL has bee

40、n historically acceptable to account for gas detection equipment accuracy considerations for compliance with 49CFR 192.736. f) Detection of a combustible gas concentration of 40% LFL or 3 LFLm (or less if defined by risk assessment) should activate a high level alarm (audible or visual, or both, as

41、most appropriate for the area) and initiate automatic disconnection of power from otherwise inappropriate electrical devices in the area. Disconnection of the devices should consider the following: 1) In a Division 2 (Zone 2) hazardous (classified) location, the power disconnecting device(s) should

42、be suitable for Class I, Division 1 or Zone 1 as appropriate if located inside the building (or similar area). A power disconnecting device listed for Division 2 may also be used within a Division 2 location. 2) If the disconnecting device(s) is located outside the building (or similar area), it sho

43、uld be suitable for the area in which it is located. Redundant or duplicate components (such as sensors) may be installed to avoid disconnecting electrical power when single component malfunctions are indicated. 3) When automatic shutdown could introduce additional or increased hazard, this method o

44、f protection should not be used. ANSI/ISA-TR12.13.03-2009 - 18 - NOTE 1 In the case of sensing 40% LFL or a combustible gas detection system malfunction, corrective action to reduce or limit the increase in gas concentration should be initiated immediately. NOTE 2 Reference ANSI/NFPA 72 for audible

45、and visual alarm device details. NOTE 3 To prevent gas migration through the conduit and/or cable system, reference ANSI/NFPA 70 “Canned Pumps, Process, or Service Connections, and ” for additional requirements on seals. g) The calibration of the combustible gas detection system should be checked an

46、d/or adjusted as necessary in accordance with the manufacturers recommendations, but at least once every three months. Checks and adjustments should verify the entire system such as test filters or by actual exposure of the sensor to a known mixture (nominal 50% LFL is recommended) of diluents and m

47、ethane or other gas anticipated, in accordance with the manufacturers recommendations, but at least once every three months. NOTE Reference ANSI/ISA-12.13.02 for combustible gas detection calibration details. h) User-provided systems that bypass the disconnecting or other “corrective action” devices

48、 to allow calibration and maintenance are permitted, provided the bypass system is utilized only during calibration or maintenance operations, and only while the area is manned by personnel who are qualified to take corrective action should there be a malfunction in process, storage, transfer, or si

49、milar equipment that potentially might release combustible gas into the area. Any systems in the bypass mode must be made continuously obvious by audible or visual means to facility personnel; and the audible or visual alarm devices must remain active while the bypass action is in effect. NOTE Reference ANSI/NFPA 72 for audible and visual alarm device details. i) When electrical equipment is installed in a location in accordance with the requirements of 4.a or 4.b, the protected location should contain no electrically heated parts or components that