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BRITISH STANDARD Installations and equipment for LNG Ð Suitability testing of gaskets designed for flanged joints used on LNG piping The European Standard EN 12308:1998 has the status of a British Standard ICS 23.040.80; 75.200 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BS EN 12308:1998 Confirmed February 2012 BS EN 12308:1998 National foreword This British Standard is the English language version of EN 12308:1998 The UK participation in its preparation was entrusted to Technical Committee GSE/38, Installations and equipment for LNG, which has the responsibility to: Ð aid enquirers to understand the text; Ð present to the responsible European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; Ð monitor related international and European developments and promulgate them in the UK A list of organizations represented on this committee can be obtained on request to its secretary Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled ªInternational Standards Correspondence Indexº, or by using the ªFindº facility of the BSI Standards Electronic Catalogue A British Standard does not purport to include all the necessary provisions of a contract Users of British Standards are responsible for their correct application Compliance with a British Standard does not of itself confer immunity from legal obligations Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages to 12, an inside back cover and a back cover This British Standard, having been prepared under the direction of the Engineering Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15 December 1998 BSI 1998 ISBN 580 30073 Amendments issued since publication Amd No Date Text affected EN 12308 EUROPEAN STANDARD NORME EUROPÊENNE EUROPẰISCHE NORM June 1998 ICS 23.040.80; 75.200 Descriptors: gas installation, gas valves, gas pipes, liquefied natural gas, pipe fittings, pipe joints, flange connections, pipe flanges, operating requirements, tests, testing conditions, clamping tests, mechanical strength, leak tests, acceptability English version Installations and equipment for LNG Ð Suitability testing of gaskets designed for flanged joints used on LNG piping Installations et eÂquipements relatifs au GNL Ð Essais d'aptitude aÁ l'emploi des joints destineÂs aux assemblages par brides des tuyauteries GNL Anlagen und AusruÈstung fuÈr FluÈssigerdgas Ð EignungspruÈfung von Flachdichtungen fuÈr Flanschverbindungen in FluÈssigerdgas Ð Rohrleitungen This European Standard was approved by CEN on May 1998 CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member This European Standard exists in three official versions (English, French, German) A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom CEN European Committee for Standardization Comite EuropeÂen de Normalisation EuropaÈisches Komitee fuÈr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1998 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members Ref No EN 12308:1998 E Page EN 12308:1998 Foreword This European Standard has been prepared by Technical Committee CEN/TC 282, Installation and equipment for LNG, 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 December 1998 and conflicting national standards shall be withdrawn at the latest by December 1998 According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom Contents Foreword Scope Normative references Definitions 3.1 liquefied natural gas (LNG) 3.2 nominal diameter (DN) 3.3 nominal pressure (PN) 3.4 NPS 3.5 Class 3.6 Class of pressure 3.7 ps (allowable pressure) 3.8 Required bolting load, Fa Design specifications of tested gaskets Technical documentation by the gasket manufacturer Check of compatibility between bolting load and mechanical strength of joint components 6.1 Compatibility with flanges 6.2 Compatibility with bolting Means and equipment required for testing 7.1 Test rig 7.2 Measuring equipment Testing 8.1 Application of bolting load 8.2 Leak testing at ambient temperature 8.3 Leak testing at cold temperature Acceptance criterion 10 Test report Annex A (informative) Thermo-mechanical behaviour of a flanged joint with gasket Annex B (informative) Test rig Annex C (normative) Method for verifying the bolting load Annex D (normative) DN equivalence for tests Annex E (normative) PN equivalence for tests Page 3 3 3 3 3 3 4 4 4 5 5 5 12 12 BSI 1998 Page EN 12308:1998 Scope Definitions This European Standard specifies the tests carried out in order to assess the suitability of gaskets designed for flanged joints used on LNG pipes This European Standard is applicable for gaskets with: Ð nominal pressure range from PN 16 to PN 100; Ð nominal diameter range from DN 10 to DN 000; Ð class range from Class 150 to Class 900; Ð nominal diameter range for Class flanges from NPS 1/4 to NPS 42 For the purposes of this standard, the following definitions and those given in EN 764, EN 1160, EN 1333 and EN ISO 6708 apply: Normative references This European Standard incorporates provisions from other publications, by dated or undated reference These normative references are cited at the appropriate places in the text and the publications are listed hereafter For dated references, subsequent amendments to or revisions of any of these publications shall apply to this European Standard only when incorporated hereto by amendment or revision For undated references, the latest edition of the publication referred to applies EN 764, Pressure equipment Ð Terminology and symbols Ð Pressure, temperature, volume EN 1160, Installations and equipment for liquefied natural gas Ð General characteristics of liquefied natural gas EN 1333, Pipework components Ð Definition and selection of PN EN 1514-1, Flanges and their joints Ð Dimensions of gaskets for PN-designated flanges Ð Part 1: Non-metallic flat gaskets with or without inserts EN 1514-2, Flanges and their joints Ð Dimensions of gaskets for PN-designated flanges Ð Part 2: Spiral wound gaskets for use with steel flanges EN 1514-3, Flanges and their joints Ð Dimensions of gaskets for PN-designated flanges Ð Part 3: Non-metallic PTFE envelope gaskets EN 1514-4, Flanges and their joints Ð Dimensions of gaskets for PN-designated flanges Ð Part 4: Corrugated, flat or grooved metallic and filled metallic gaskets for use with steel flanges prEN 1515-1, Flanges and their joints Ð Bolting Ð Part 1: Selection of bolting prEN 1515-2, Flanges and their joints Ð Bolting Ð Part 2: Combination of flange and bolting materials for steel flanges Ð PN designated EN ISO 6708, Pipework components Ð Definition and selection of DN (nominal size) (ISO 6708:1995) 3.1 liquefied natural gas (LNG) see EN 1160 3.2 nominal diameter (DN) see EN ISO 6708 3.3 nominal pressure (PN) see EN 1333 3.4 NPS a numerical designation of size used only in association with metricated flanges of ANSI origin, which is common to all components in a piping system other than those designated by outside diameter; it is a convenient round number for reference purposes which is normally only loosely related to the manufacturing dimensions in inches NOTE It is designated by the letters NPS followed by a number NOTE The NPS cannot be subject to measurement and cannot be used for the purpose of calculation 3.5 class a numerical designation for reference purposes, used only for metricated flanges of ANSI origin NOTE It is designated by the word ªClassº, followed by the appropriate reference number NOTE The number following the word ªClassº does not represent a measurable value and therefore cannot be used in calculations or followed by a unit NOTE The maximum allowable pressure depends upon the Class number, the material and design of the component The corresponding allowable temperature etc is given in the tables of the p/T-ratings in the appropriate standards 3.6 class of pressure the PN or class of a component 3.7 allowable pressure (ps) see EN 764 3.8 required bolting load (Fa) the load to be applied to ensure the tightness of the joint in normal operating conditions Design specifications of tested gaskets The gasket subjected to the suitability tests defined in this standard shall fulfil the requirements of EN 1514-1 to EN 1514-4, prEN 1515-1 and prEN 1515-2 and wherever necessary, the requirements of EN 1160 BSI 1998 Page EN 12308:1998 Technical documentation by the gasket manufacturer The manufacturer shall supply the technical documentation applicable to the gasket, and in particular: a) the dimensional characteristics of the gasket; b) the assembly drawings for the gasket; c) the required bolting load Fa of the joint designed to ensure tightness under the following conditions: 1) operating temperature ranging from 2165 8C to + 60 8C; 2) operating pressure ranging from Pa to 1,15 times the allowable pressure (ps) of the joint d) the thickness of the gasket and the stacking height, H, of the flanges (see Figure C.2) after tightening with the required bolting load Fa When calculating the required bolting load Fa of the joint to the test conditions defined above, the manufacturer shall take into account the following: Ð the characteristics of the selected bolting; Ð the reversible loosening of the bolting due to the differences in the thermal state of the joint components during cool-down; Ð the irreversible loosening of the bolting due to changes in the relative positioning of the joint components during the first few cool-downs Annex A describes the thermal and mechanical stresses to which the gasket in a flanged joint is subjected, and suggests how the joint is tightened Check of compatibility between bolting load and mechanical strength of joint components 6.1 Compatibility with flanges It is required to check with calculations of mechanical strength that the required bolting load Fa does not generate any permanent distortion of the flanges under the conditions of thermo-mechanical stress defined in Table 6.2 Compatibility with bolting It is necessary to check with calculations of mechanical strength that the required bolting load Fa can be applied without generating any permanent distortion of the bolts Compatibility shall be regarded as demonstrated if the following condition is satisfied: Fa # n Fb where: n is the number of bolts; Fb is the maximum allowable load of each bolt The load Fa shall be calculated based on the assumption that the bolt is subjected to a pure traction load, to a deflection load resulting from flaring-out of the flanges caused by the bolting, and possibly to a torsion load generated by the means of tightening the bolt Means and equipment required for testing 7.1 Test rig Attention is drawn to European safety regulations for the design and operation of the test rig It shall consist of two assembled spool pieces between which the gasket to be tested is positioned The spools shall be fitted with branch-tees providing for: Ð LNG supply; Ð draining of the test rig; Ð pressurising of the test rig; Ð measurement of temperature and pressure of the gas or LNG contained in the spools Annex B specifies the characteristics of the test rig NOTE Liquid nitrogen can replace LNG in the spools provided the appropriate detector is used to measure the possible leakages 7.2 Measuring equipment The following devices shall be used to measure the conditions under which the gasket is tested: Ð a hydraulic tightener or torque wrench to tighten the bolts; Ð a micrometer graduated every 0,01 mm to determine the bolting load when assembling the joint, or any other similar precision instrument; Ð a temperature probe to measure the gas or LNG temperature inside the test rig; Ð a pressure transmitter or a manometer to measure the internal pressure of the rig; Ð a gas detector with a minimum threshold of at least 10 % of the methane low flammability limit in air to detect any gas leakage from the gasket during an LNG test; Ð a temperature probe arranged at the upper periphery of one flange to check the thermal state of the joint during cool-down Table Ð Stresses to be taken into account when checking the mechanical strength of flanges Nature of stress Values Temperature 15 8C Joint internal relative pressure Mechanical load 1,15 ps Fa Cool-down From 15 8C to 2165 8C for the following duration: when DN # 150; 15 when 150 < DN # 300; 60 when 300 < DN # 1000 1,15 ps Fa BSI 1998 Page EN 12308:1998 Testing Acceptance criterion 8.1 Application of bolting load The joint bolting shall be tightened at ambient temperature such that the relative deviation between the achieved bolting loads and the required bolting load of each bolt shall range between % and + 10 % The bolting load shall be verified in accordance with annex C A gasket shall be regarded as suitable for use in flanged joints of LNG pipes provided that the leak tightness tests specified in 8.2 and 8.3 have proved conclusive It is not necessary to carry out such tests on all gaskets presenting the same basic design, except the dimensions Table D.1 specifies the allowable range of DN which are qualified for each DN tested Table E.1 specifies the allowable range of PN which are qualified for each PN tested 8.2 Leak testing at ambient temperature The gasket shall be checked for tightness with gas (air, natural gas, nitrogen) at pressure stages for min, corresponding to 0,25 ps 0,5 ps ps and 1,15 ps At each of the above pressure stages, leak tightness shall be checked by applying soap suds between the flanges of the joint The test shall be regarded as conclusive if no soap bubble forms 8.3 Leak testing at cold temperature Five testing cycles shall be carried out at cold temperature in accordance with the following operational procedure: a) fill the test rig with LNG, with filling time as specified in Table 2; Table Ð Test rig filling time as a function of the DN DN time t DN # 150 # t # 15 150 < DN # 300 15 # t # 60 300 < DN # 000 60 # t # 120 b) cool-down the test rig by circulating LNG; c) stop the LNG circulation once the joint cooling rate is less than 10 8C/h over a period of 15 min; d) check the leak tightness of the joint; The check of leak tightness at cold temperature shall consist of checking for the absence of any leakage with a gas detector over the entire outer circumference of the joint, at pressure stages for min, corresponding to 0,25 ps, 0,5 ps, ps and 1,15 ps e) drain the test rig to allow warming up to ambient temperature; f) repeat the ambient temperature test in conformity with 8.2 NOTE The pressure increase from one stage to the next can be achieved by simple warming-up of the LNG contained in the rig BSI 1998 10 Test report The results from the above test shall be recorded in a test report listing the following data: a) name of testing company, name of tester and signature; b) date of test report; c) technical data sheet of gasket; d) tested gasket characteristics, in particular its DN or NPS and class of pressure; e) required bolting load of the joint as supplied by manufacturer as well as the calculation details; f) achieved bolting load; g) the bolting load uncertainty; h) thermal conditions of test at cold temperature characterized by ambient temperature, LNG temperature and temperature at the upper periphery of the flange; i) results from the leak tightness tests at ambient and cold temperatures and curves reporting the evolution of pressure during the tests; j) DN values of the gaskets qualified on the basis of this test; k) classes of pressure of the gaskets qualified on the basis of this test Page EN 12308:1998 Annex A (informative) Thermo-mechanical behaviour of a flanged joint with gasket A.1 General comments In cryogenic applications, a joint undergoes reversible and irreversible loosening processes resulting from the successive cool-down operations to which it is subjected These loosening processes should be taken into account when determining the bolting load which should in addition be compatible with the mechanical strength of the various components in the joint A.2 Reversible loosening The reversible loosening occurring at cool-down time and disappearing once the joint has returned to ambient temperature results from the following causes: Ð the thermal state of the bolts which are warmer than the rest of the joint, due to their peripheral position; Ð the thermal behaviour of the bolts whenever the bolts are built in a material presenting a lower thermal expansion coefficient than the flange material A.3 Irreversible loosening Following a cooling and warming cycle, the bolting tension is partially relaxed This irreversible loosening is significant after the first cooling and warming cycle, decreases for the next four cycles and becomes negligible thereafter The irreversible loosening process results from a change in the relative position of the joint components, and more specifically of the bolts in relation to the flanges It is not affected either by the LNG pressure nor by the cool-down rate A.4 Evolution of tightening during the successive cooling and warming cycles Figure A.1 represents the changes in the average compressive stress of the gasket during the first five cooling and warming cycles NOTE In the case of cryogenic joints, X8Ni steel is commonly used to manufacture bolts, while the basic flange material is X4CrNi 18-10 steel Considering their respective thermal expansion coefficients (13,8 1026 K21 for X4CrNi 18-10 steel and 9,4 1026 K21 for X8Ni steel), the cool-down causes a decreased compression on the gasket Both phenomena generate differential contractions between the flange and the bolts, and cause a loosening which may be determined theoretically via a calculation based on a finite element method BSI 1998 Page EN 12308:1998 A BD TA ± TE TE ± TC Initial tightening Cool-down Irreversible loosening Reversible loosening Figure A.1 Ð Changes in the average compressive stress during successive cooling and warming cycles BSI 1998 Page EN 12308:1998 Annex B (informative) Test rig Dimensions in millimetres Gasket to be tested LNG supply to test rig Nitrogen pressurization Measurements of temperature and pressure Drain valve LNG tank Measurement of temperature at the upper periphery of the flange Measurement of ambient temperature Figure B.1 Ð Diagram of test rig BSI 1998 Page EN 12308:1998 Annex C (normative) Method for verifying the bolting load C.1 Measurement of bolt length Two centering holes shall be drilled as defined in Figure C.1, at each end of the bolts for purposes of measuring their length using a precision micrometer C.2 Measurement of elongation of bolts The elongation DLi of a bolt referenced i is expressed as follows: DLi = Lfi Loi where: Lfi Loi is the length after tightening the bolt referenced i; is the initial length before tightening the bolt referenced i C.3 Calculation of the bolting load achieved with each bolt The bolting load achieved with each bolt shall be calculated by taking into account the dimensions of the tightened joint components as defined in Figure C.2 The achieved bolting load Fsi of the bolt referenced i has the following expression: Fsi = K DLi where: K is the stiffness coefficient of the bolt barrel The stiffness coefficient K of the bolt barrel shall be calculated as follows: K= + 1 K1 K2 where: K1 K2 is the stiffness coefficient of the unthreaded portion of the bolt; is the stiffness coefficient of the threaded portion of the bolt BSI 1998 The stiffness coefficient K1 has the following expression: E S1 K1 = L1 where: E S1 L1 is the Young modulus of the material of the bolt; is the area of the unthreaded portion of the bolt (diameter D1); is the length of the unthreaded portion of the bolt The stiffness coefficient K2 has the following expression: E S2 K2 = L2 where: S2 Lf is the core area of the threaded portion of the bolt (diameter D2); is the active length of the threaded portion of the bolt The active length of the threaded portion is expressed as follows: L2 = H L1 + Lf where: H Lf is the stacking height of the flanges; is the effective length of each nut conveying the bolting load NOTE The recommended effective length Lf corresponds to the half height of the nut C.4 Calculation of the acceptance criterion of the achieved bolting load The relative difference between the achieved bolting DF1 load and the required bolting load of each bolt has Fa n the following expression: F Fsi a DFi n = Fa Fa n n Page 10 EN 12308:1998 Bolt to be measured Micrometer Centering hole Figure C.1 Ð Measurement of the length of bolts BSI 1998 Page 11 EN 12308:1998 Figure C.2 Ð The dimensions of tightened joint components required for calculation of the bolting load BSI 1998 Page 12 EN 12308:1998 Annex D (normative) DN equivalence for tests Table D.1 Ð Table of DN equivalence for tests DN tested 10 15 20 25 32 40 50 80 100 125 150 200 NPS tested ï ¯ 1ï 1¯ DN of qualified gaskets 10 15 20 10 15 20 25 15 20 25 32 20 25 32 40 25 32 40 50 32 40 50 80 40 50 80 100 50 80 100 125 80 100 125 150 100 125 150 200 125 150 200 250 150 200 250 300 DN tested 250 300 350 400 450 500 600 700 750 800 900 1000 NPS tested 10 12 14 16 18 20 24 28 30 32 36 42 DN of qualified gaskets 200 250 300 350 400 450 500 600 700 750 800 900 250 300 350 300 350 400 350 400 450 400 450 500 450 500 600 500 600 700 600 700 750 700 750 800 750 800 900 800 900 100 900 1000 1000 NOTE If the DN of the tested gasket is 50, all gaskets presenting the same basic design from DN 40 to DN 100 are qualified NOTE The required bolting load Fa of the tested gasket is only representative for the DN and PN of the test Annex E (normative) PN equivalence for tests Table E.1 Ð Table of PN equivalence for tests Class tested 600 PN tested 100 63 300 PN of qualified gaskets 100 63 100 63 40 63 40 25 40 63 40 25 16 25 40 25 16 150 40 25 16 16 25 16 NOTE If the PN of the tested gasket is 63, all gaskets presenting the same basic design from PN 40 to PN 100 are qualified NOTE The required bolting load Fa of the tested gasket is only representative for the DN and PN of the test BSI 1998 blank BSI 389 Chiswick High Road London W4 4AL | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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