API 521 Pressurerelieving and Depressuring Systems(英文版)（可编辑）

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1、API 521-2007 Pressure-relieving and Depressuring Systems(英文版) Pressure-relieving and Depressuring Systems ANSI/API STANDARD 521 FIFTH EDITION, JANUARY 2007 ISO 23251 Identical , Petroleum and natural gas industriesPressure-relieving and depressuring systems Special Notes API publications necessarily

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9、cording, or otherwise, without prior written permission from the publisher. Contact the Publisher, API Publishing Services, 1220 L Street, N.W., Washington, D.C. 20005. Copyright ? 2006 American Petroleum Institute API Standard 521 / ISO 23251 API Foreword Nothing contained in any API publication is

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15、org. ii Contents Page API Foreword . ii Foreword . v Introduction . vi 1 Scope . 1 2 Normative references . 1 3 Terms and definitions . 1 4 Causes of overpressure . 10 4.1 General . 10 4.2 Overpressure protection philosophy . 10 4.3 Potentials for overpressure . 11 4.4 Recommended minimum relief sys

16、tem design content . 17 4.5 List of items required in flare-header calculation documentation . 20 4.6 Guidance on vacuum relief. 20 5 Determination of individual relieving rates. 22 5.1 Principal sources of overpressure . 22 5.2 Sources of overpressure . 24 5.3 Effects of pressure, temperature, and

17、composition . 24 5.4 Effect of operator response . 24 5.5 Closed outlets . 24 5.6 Cooling or reflux failure . 25 5.7 Absorbent flow failure . 26 5.8 Accumulation of non-condensables . 26 5.9 Entrance of volatile material into the system . 26 5.10 Failure of process stream automatic controls . 27 5.1

18、1 Abnormal process heat input . 29 5.12 Internal explosion excluding detonation . 30 5.13 Chemical reaction . 30 5.14 Hydraulic expansion . 31 5.15 External pool fires . 36 5.16 Jet fires . 51 5.17 Opening manual valves . 51 5.18 Electric power failure . 51 5.19 Heat-transfer equipment failure . 52

19、5.20 Vapour depressuring . 55 5.21 Special considerations for individual pressure-relief devices . 63 5.22 Dynamic simulation . 64 6 Selection of disposal systems . 65 6.1 General . 65 6.2 Fluid properties that influence design . 65 6.3 Atmospheric discharge . 66 6.4 Disposal by flaring . 76 6.5 Dis

20、posal to a lower-pressure system .95 6.6 Disposal of liquids and condensable vapours . 96 7 Disposal systems . 97 7.1 Definition of system design load . 97 7.2 System arrangement . 100 7.3 Design of disposal system components . 102 7.4 Flare gas recovery systems . 137 ISO 23251:2006 E Annex A inform

21、ative Determination of fire relief requirements. 142 Annex B informative Special system design considerations . 146 Annex C informative Sample calculations for sizing a subsonic flare stack. 149 Annex D informative Typical details and sketches. 166 Annex E informative High integrity protection syste

22、ms HIPS . 169 Bibliography . 176 iv API Standard 521 / ISO 23251 ISO 23251:2006 E Foreword ISO the International Organization for Standardization is a worldwide federation of national standards bodies ISO member bodies . The work of preparing International Standards is normally carried out through I

23、SO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates

24、closely with the International Electrotechnical Commission IEC on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Dr

25、aft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this doc

26、ument may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 23251 was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore structures for petroleum, petrochemical and natural gas industries, Subcommittee SC 6

27、, Processing equipment and systems. This corrected version of ISO 23251:2006 incorporates corrections to Table 4, column 2, second row under the header, and the five rows of data in column 3. v v ISO 23251:2006 E API Standard 521 / ISO 23251 Introduction The portions of this International Standard d

28、ealing with flares and flare systems are an adjunct to API Std 537 10, which addresses mechanical design, operation and maintenance of flare equipment. It is important for all parties involved in the design and use of a flare system to have an effective means of communicating and preserving design i

29、nformation about the flare system. To this end, API has developed a set of flare data sheets, which can be found in of API Std 537, Appendix A. The use of these data sheets is both recommended and encouraged as a concise, uniform means of recording and communicating design information. vi vi API Sta

30、ndard 521 / ISO 23251 INTERNATIONAL STANDARD ISO 23251:2006 E Petroleum, petrochemical and natural gas industries Pressure-relieving and depressuring systems 1 Scope This International Standard is applicable to pressure-relieving and vapour-depressuring systems. Although intended for use primarily i

31、n oil refineries, it is also applicable to petrochemical facilities, gas plants, liquefied natural gas LNG facilities and oil and gas production facilities. The information provided is designed to aid in the selection of the system that is most appropriate for the risks and circumstances involved in

32、 various installations. This International Standard is intended to supplement the practices set forth in ISO 4126 or API RP 520-I for establishing a basis of design. This International Standard specifies requirements and gives guidelines for examining the principal causes of overpressure; and determ

33、ining individual relieving rates; and selecting and designing disposal systems, including such component parts as piping, vessels, flares, and vent stacks. This International Standard does not apply to direct-fired steam boilers. Piping information pertinent to pressure-relieving systems is presente

34、d in . 2 Normative 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. ISO 4126 all parts ,

35、Safety devices for protection against excessive pressure API RP 520-I:2000, Sizing, Selection and Installation of Pressure-Relieving Devices in Refineries Part I : Sizing and Selection 1 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 accumul

36、ation pressure increase over the imum allowable working pressure of the vessel allowed during discharge through the pressure-relief device NOTE Accumulation is expressed in units of pressure or as a percentage of MAWP or design pressure. imum allowable accumulations are established by pressure-design codes for emergency operating and fire contingencies. 1 American Petroleum Institute, 1220 L Street, N.W., Washington, D.C., 20005-4070, USA. 1