1、BRITISH STANDARDBS EN ISO 23251:2007 +A1:2008Incorporating corrigendum August 2007Petroleum, petrochemical and natural gas industries Pressure-relieving and depressuring systemsICS 75.180.20g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g
2、51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN ISO 23251:2007+A1:2008This British Standard was published under the authority of the Standards Policy and Strategy Committee on 29 September 2006 BSI 2008ISBN 978 0 580 61979 3National forewordThis Britis
3、h Standard is the UK implementation of EN ISO 23251:2007+A1:2008. It is identical with ISO 23251:2006, incorporating amendment 1:2008 and corrigendum August 2007. It supersedes BS EN ISO 23251:2007 which is withdrawn.The start and finish of text introduced or altered by amendment is indicated in the
4、 text by tags. Tags indicating changes to ISO text carry the number of the ISO amendment. For example, text altered by ISO amendment 1 is indicated by !“.The start and finish of text introduced or altered by corrigendum is indicated in the text by tags. Text altered by ISO corrigendum August 2007 is
5、 indicated in the text by .The UK participation in its preparation was entrusted by Technical Committee PSE/17, Materials and equipment for petroleum, petrochemical and natural gas industries, to Panel PSE/17/-/6, Processing equipment and systems for petroleum and natural gas industries.A list of or
6、ganizations represented on this subcommittee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal ob
7、ligations.Amendments/corrigenda issued since publicationAmd. No. Date Comments17355 31 August 2007 Renumbers BS ISO 23251:2006 as BS EN ISO 23251:200730 September 2008 Implementation of ISO amendment 1:2008 with CEN endorsement A1:2008. Implementation of ISO corrigendum August 2007EUROPEAN STANDARDN
8、ORME EUROPENNEEUROPISCHE NORMEN ISO 23251:2007+A1May 2008ICS 75.180.20English VersionPetroleum, petrochemical and natural gas industries - Pressure-relieving and depressuring systems (ISO 23251:2006)Industries du ptrole, de la ptrochimie et du gaz naturel -Systmes de dpressurisation et de protection
9、 contre lessurpressions (ISO 23251:2006)Erdl-, petrochemische und Erdgasindustrie -Druckentlastungs- und Druckausgleichssysteme (ISO23251:2006)This European Standard was approved by CEN on 12 July 2007.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the cond
10、itions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three
11、official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austri
12、a, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE
13、 FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2007 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 23251:2007: EForeword The text of ISO 232
14、51:2006 has been prepared by Technical Committee ISO/TC 67 “Materials, equipment and offshore structures for petroleum and natural gas industries” of the International Organization for Standardization (ISO) and has been taken over as EN ISO 23251:2007 by Technical Committee CEN/TC 12 “Materials, equ
15、ipment and offshore structures for petroleum, petrochemical and natural gas industries“, the secretariat of which is held by AFNOR. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by January 2008, an
16、d conflicting national standards shall be withdrawn at the latest by January 2008. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Den
17、mark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. Endorsement notice The text of ISO 23251:2006 has been approved
18、by CEN as EN ISO 23251:2007 without any modifications. BS EN ISO 23251:2007+A1:2008Foreword to amendment A1 This document (EN ISO 23251:2007/A1:2008) has been prepared by Technical Committee ISO/TC 67 “Materials, equipment and offshore structures for petroleum and natural gas industries” in collabor
19、ation with Technical Committee CEN/TC 12 “Materials, equipment and offshore structures for petroleum, petrochemical and natural gas industries” the secretariat of which is held by AFNOR. This Amendment to the European Standard EN ISO 23251:2007 shall be given the status of a national standard, eithe
20、r by publication of an identical text or by endorsement, at the latest by November 2008, and conflicting national standards shall be withdrawn at the latest by November 2008. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and
21、/or CENELEC shall not be held responsible for identifying any or all such patent rights. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republi
22、c, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of ISO 23251:2007/Amd 1:20
23、08 has been approved by CEN as EN ISO 23251:2007/A1:2008 without any modification. iiiContents Page Introduction v 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
24、. 11 4.4 Recommended minimum relief system 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 Effec
25、ts of pressure, temperature, and 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
26、automatic controls. 27 5.11 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 equipme
27、nt failure 52 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 66 6.1 General. 66 6.2 Fluid properties that influence design 67 6.3 Atmospheric discharge 68 6.4 Disposal by flaring 78 6.5 Disp
28、osal to a lower-pressure system . 97 6.6 Disposal of liquids and condensable vapours 98 7 Disposal systems 100 7.1 Definition of system design load 100 7.2 System arrangement 102 7.3 Design of disposal system components 104 7.4 Flare gas recovery systems. 141 5.23 Overfilling process or surge vessel
29、 65 6.7 Disposal through common vent stack . 99 BS EN ISO 23251:2007+A1:2008iv Annex A (informative) Determination of fire relief requirements. 146 Annex B (informative) Special system design considerations 150 Annex C (informative) Sample calculations for sizing a subsonic flare stack. 153 Annex D
30、(informative) Typical details and sketches. 170 Annex E (informative) High integrity protection systems (HIPS) 173 Bibliography . 180 BS EN ISO 23251:2007+A1:2008vBS EN ISO 23251:2007+A1:2008Introduction This International Standard is based on the draft 5th edition of API RP 521, with the intent tha
31、t the 6th edition of API RP 521 will be identical to this International Standard. The portions of this International Standard dealing 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 a
32、ll parties involved in the design and use of a flare system to have an effective means of communicating and preserving design information 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
33、is both recommended and encouraged as a concise, uniform means of recording and communicating design information. blank1Petroleum, petrochemical and natural gas industries Pressure-relieving and depressuring systems 1 Scope This International Standard is applicable to pressure-relieving and vapour-d
34、epressuring systems. Although intended for use primarily in 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
35、most appropriate for the risks and circumstances involved in 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 fo
36、r examining the principal causes of overpressure; and determining 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 inf
37、ormation pertinent to pressure-relieving systems is presented in 7.3.1. 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
38、 document (including any amendments) applies. ISO 4126 (all parts), 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 Selection1)3 Terms and definitions For the purposes of thi
39、s document, the following terms and definitions apply. 3.1 accumulation pressure increase over the maximum 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 pre
40、ssure. Maximum 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. BS EN ISO 23251:2007+A1:20082 3.2 administrative controls procedures intended to en
41、sure that personnel actions do not compromise the overpressure protection of the equipment 3.3 assist gas combustible gas that is added to relief gas prior to the flare burner or at the point of combustion in order to raise the heating value 3.4 atmospheric discharge release of vapours and gases fro
42、m pressure-relieving and depressuring devices to the atmosphere 3.5 back pressure pressure that exists at the outlet of a pressure-relief device as a result of the pressure in the discharge system NOTE The back pressure is the sum of the superimposed and built-up back pressures. 3.6 balanced pressur
43、e-relief valve spring-loaded pressure-relief valve that incorporates a bellows or other means for minimizing the effect of back pressure on the operational characteristics of the valve 3.7 blowdown depressurization of a plant or part of a plant, and equipment NOTE Not to be confused with the differe
44、nce between the set pressure and the closing pressure of a pressure-relief valve. 3.8 blow-off loss of a stable flame where the flame is lifted above the burner, occurring if the fuel velocity exceeds the flame velocity 3.9 breaking-pin device pressure-relief device actuated by static differential o
45、r static inlet pressure and designed to function by the breakage of a load-carrying section of a pin that supports a pressure-containing member 3.10 buckling pin device pressure-relief device actuated by static differential or static inlet pressure and designed to function by the buckling of an axia
46、lly-loaded compressive pin that supports a pressure-containing member 3.11 built-up back pressure increase in pressure at the outlet of a pressure-relief device that develops as a result of flow after the pressure-relief device opens 3.12 buoyancy seal dry vapour seal that minimizes the amount of pu
47、rge gas needed to protect against air infiltration NOTE The buoyancy seal functions by trapping a volume of light gas in an internal inverted compartment; this prevents air from displacing buoyant light gas in the flare. BS EN ISO 23251:2007+A1:200833.13 burnback internal burning within the flare ti
48、p NOTE Burnback can result from air backing down the flare burner at purge or low flaring rates. 3.14 burning velocity flame velocity speed at which a flame front travels into an unburned combustible mixture 3.15 burn-pit flare open excavation, normally equipped with a horizontal flare burner that c
49、an handle liquid as well as vapour hydrocarbons 3.16 burst pressure value of the upstream static pressure minus the value of the downstream static pressure just before a rupture disk bursts NOTE If the downstream pressure is atmospheric, the burst pressure is the upstream static gauge pressure. 3.17 closed disposal system disposal system capable of containing pressures that are different from atmospheric pressure 3.18 cold differential test pressure CDTP pressure at which a pressure-relief valve is adjusted to open on the test stand NOTE The cold differential test pre
