BS_746-2014.pdf

BS746:2014BRITISH STANDARDForewordPublishing informationThis British Standard is published by BSI Standards Limited,under licence fromThe British Standards Institution,and came into effect on 30 November 2014.Itwas prepared by Technical Committee GSE/25,Gas meters.A list of organizationsrepresented on this committee can be obtained on request to its secretary.SupersessionBS 746:2014 supersedes BS 746:2005+A1:2009,which is withdrawn.Relationship with other publicationsThis standard specifies fittings to be used in conjunction with gas meters such asthose specified by BS EN 1359 and BS EN 14236.Information about this documentThis is a full revision of the standard,and introduces the following principalchanges.Dimensional changes have been made to ensure that the flat parts of thenuts engage directly on the flat parts of the liners such that even pressure isapplied to the surfaces of the washers.The properties of the sealing washer have been redefined.Additional tests for fittings and washer performance have been added.Hexagonal nuts are now permitted as an alternative to octagonal nuts.This document may be used in the procurement of fittings.Presentational conventionsThe provisions of this standard are presented in roman(i.e.upright)type.Itsrequirements are expressed in sentences in which the principal auxiliary verb isshall.Commentary,explanation and general informative material is presented insmaller italic type,and does not constitute a normative element.Contractual and legal considerationsThis publication does not purport to include all the necessary provisions of acontract.Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legalobligations.iThe British Standards Institution2014BRITISH STANDARDBS746:20141 ScopeThis British Standard specifies requirements and test methods for unions andadaptors for the installation of low pressure gas meters.It is applicable tounions and adaptors for gas meters for use with 1st,2nd and 3rd family gases attemperatures between-20 C and+60 C,up to a maximum operating pressureof 75 mbar 1)and a maximum incidental pressure of 200 mbar.The gas tightnessof the gas meter unions and adaptors is also specified.NOTE The tests specified in this standard are type tests,except for that specifiedin4.2.3.2 Normative referencesThe following referenced documents are indispensable for the application ofthis document.For dated references,only the edition cited applies.For undatedreferences,the latest edition of the referenced document(including anyamendments)applies.BS 1936-1,Undercuts and runouts for screw threads-Part 1:Inch screw threadsBS 7371-6,Coatings on metal fasteners-Part 6:Specification for hot dippedgalvanized coatingsBS EN 549,Specification for rubber materials for gas appliances and gasequipmentBS EN 1562,Founding-Malleable cast ironsBS EN 1652,Copper and copper alloys-Plate,sheet,strip and circles for generalpurposesBS EN 1976,Copper and copper alloys-Cast unwrought copper productsBS EN 1982,Copper and copper alloys-Ingots and castingsBS EN 10088-3:2005,Stainless steels-Part 3:Technical delivery conditions forsemi-finished products,bars,rods,wire,sections and bright products ofcorrosion resisting steels for general purposesBS EN 10242,Threaded pipe fittings in malleable cast ironBS EN 12164,Copper and copper alloys-Rod for free machining purposesBS EN 12165,Copper and copper alloys-Wrought and unwrought forging stockBS EN 12167,Copper and copper alloys-Profiles and rectangular bar forgeneral purposesBS EN 12168,Copper and copper alloys-Hollow rod for free machiningpurposesBS EN 12329:2000,Corrosion protection of metals-Electrodeposited coatings ofzinc with supplementary treatment on iron or steelBS EN 12420,Copper and copper alloys-ForgingsBS EN ISO 27830,Metallic and other inorganic coatings-Guidelines forspecifying metallic and inorganic coatingsPD 970,Wrought steels for mechanical and allied engineering purposesRequirements for carbon,carbon manganese and alloy hot worked or coldfinished steels1)1 bar 105 N/m2 100 kPa.The British Standards Institution20141