Bsi bs en 00817 2008 (2009)

Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BRITISH STANDARD Sanitary tapware — Mechanical mixing valves (PN 10) — General technical specifications ICS 91.140.70, NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS EN 817:2008 Incorporating Corrigendum January 2009 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 National foreword This British Standard is the UK implementation of EN 817:2008 It supersedes BS EN 817:1998 and which is withdrawn The UK participation in its preparation was entrusted to Technical Committee B/504/8, Sanitary tapware A list of organizations represented on this committee 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 obligations This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 December 2008 © BSI 2009 ISBN 978 580 66666 Amendments/corrigenda issued since publication Date Comments 31 January 2009 Correction to low resolution images Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EUROPEAN STANDARD EN 817 NORME EUROPÉENNE EUROPÄISCHE NORM June 2008 ICS 91.140.70 Supersedes EN 817:1997 English Version Sanitary tapware - Mechanical mixing valves (PN 10) - General technical specifications Robinetterie sanitaire - Mitigeurs mécaniques (PN 10) Spécifications techniques générales Sanitärarmaturen - Mechanisch einstellbare Mischer (PN 10) - Allgemeine technische Spezifikation This European Standard was approved by CEN on 29 May 2008 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 CEN Management Centre 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 CEN Management Centre has the same status as the official versions CEN members are the national standards bodies of Austria, 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 FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG Management Centre: rue de Stassart, 36 © 2008 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members B-1050 Brussels Ref No EN 817:2008: E Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) Contents page Foreword Introduction Scope Normative references 10 3.1 3.2 Terms, definitions and designation 10 Terms and definitions 10 Designation 11 4.1 4.2 Marking and identification 11 Marking 11 Identification .12 5.1 5.2 Materials .12 Chemical and hygiene requirements 12 Exposed surface conditions .12 6.1 6.2 6.3 6.4 6.5 6.6 6.7 Dimensional characteristics .12 General remarks 12 Inlet dimensions 12 Outlet dimensions 17 Mounting dimensions 19 Special cases .20 Flexible hoses for shower outlets 20 Shower outlets .20 Sequence of testing 21 8.1 8.2 8.3 8.4 8.5 8.6 8.7 Leaktightness characteristics 21 General 21 Test methods 21 Leaktightness of the obturator and of the mixing valve upstream of the obturators with the obturator in the closed position .22 Leaktightness of the mixing valve downstream of the obturator with the obturator open 22 Leaktightness of manually operated diverter 22 Leaktightness and operation of diverter with automatic return .23 Leaktightness of the obturator: cross flow between hot water and cold water 24 9.1 9.2 9.3 9.4 9.5 Pressure resistance characteristics – mechanical performance under pressure 26 General 26 Principle 26 Apparatus .26 Mechanical behaviour upstream of the obturator – obturator in the closed position 26 Mechanical behaviour downstream of the obturator – obturator in the open position .26 10 10.1 10.2 10.3 10.4 10.5 10.6 10.7 Hydraulic characteristics 27 General 27 Initial settings .27 Principle 28 Apparatus .28 Procedure .28 Determination of flow rate 29 Determination of sensitivity 30 11 Mechanical strength characteristics - torsion test for operating mechanism 33 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) 11.1 11.2 General 33 Test method 33 12 12.1 12.2 12.3 Mechanical endurance characteristics 34 Mechanical endurance of the control device 34 Mechanical endurance of diverters 38 Mechanical endurance of swivel spouts 40 13 Backflow protection 41 14 14.1 14.2 14.3 Acoustic characteristics .41 General 41 Procedure .41 Requirements .41 Annex A (informative) Apparatus 43 Annex B (informative) Pressure take-off tee .47 Bibliography 50 ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) Figures Figure Supply system with a pressure range of (0,05 to 1,0) MPa [(0,5 to 10) bar] Figure Flexible hoses and plain tube .14 Figure Multi-hole mechanical mixing valve 15 Figure Supply connections for mechanical mixing valve and remote outlets 16 Figure Remote outlet .18 Figure Single hole mechanical mixing valve .18 Figure Two hole mechanical mixing valve 18 Figure Single hole mechanical mixing valve .19 Figure Two hole mechanical mixing valve 20 Figure 10 Sensitivity curve 31 Figure 11 Radius for the determination of sensitivity .32 Figure 12 Rectangular movement .34 Figure 13 Triangular movement 35 Figure 14 Test bench adjustment torque for conventionnal mixing valve 37 Figure 15 Test bench adjustment torque for joystick mixing valve .37 Figure 16 Test bench adjustment torque for sequential mixing valve 37 ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Figure A Supply circuits 43 Figure A Test circuit .45 Figure A Mounting of the mixing valve 46 Figure B Pressure take-off tee 47 Figure B Schematic examples of pressure take-off tees 48 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) Tables Table Conditions of use/Classifications Table Designation 11 Table Inlet dimensions (mechanical mixing valve) 13 Table Outlet dimensions (Remote outlets, mechanical mixing valve) .17 Table Mounting dimensions (Outlets, single- and multi-hole mechanical mixing valve) .19 Table Test Sequence .21 Table Summary of leaktightness tests 25 Table Summary of pressure resistance characteristic tests 27 Table Initial Settings 27 Table 10 Flow rates according to application 29 Table 11 Performance levels 30 Table 12 Summary of test conditions for cartridges .35 Table 13 Summary of test conditions for diverters 39 Table 14 Flow rate classes (EN ISO 3822-4 Annex A) 41 Table 15 Acoustic group 42 Table A Connecting dimension 45 Table B Dimensions of the pressure take-off tee 47 ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) Foreword This document (EN 817:2008) has been prepared by Technical Committee CEN/TC 164 “Water supply”, 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 2008, and conflicting national standards shall be withdrawn at the latest by December 2008 Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights This document supersedes EN 817:1997 This European Standard acknowledges the field of application for mechanical mixing valves used in water supply systems with a pressure range of (0,05 to 1,0) MPa (0,5 bar to 10 bar) 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, 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 ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) Introduction In respect of potential adverse effects on the quality of water intended for human consumption, caused by the product covered by this European Standard This European Standard provides no information as to whether the product can be used without restriction in any of the Member States of the EU or EFTA It should be noted that, while awaiting the adoption of verifiable European criteria, existing national regulations concerning the use and/or the characteristics of these products remain in force This document identifies characteristics and technical requirements for mechanical mixing valves ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) Scope This European Standard specifies:  the dimensional, leaktightness, pressure resistance, hydraulic performance, mechanical strength, endurance and acoustic characteristics with which mechanical mixing valves need to comply;  test methods to verify the characteristics The tests described in this European Standard are type tests (laboratory tests) and not quality control tests carried out during manufacture This European Standard applies to PN 10 mechanical mixing valves for use with sanitary appliances installed in rooms used for bodily hygiene (cloakrooms, bathrooms, etc.) and in kitchens, i.e for use with baths, wash basins, bidets, showers and sinks The conditions of use and classifications are given in Table — Conditions of use/classifications Water supply system Pressure Temperature a NOTE Operating range of mechanical mixing valves Limits Dynamic pressure > 0,05 MPa (0,5 bar) Static pressure ≤ 1,0 MPa (10,0 bar) ≤ 90 °C Recommended Flow rate classes Acoustics Marking See See Clause 14 See Clause Z ≤ 0,15 l/s A ≤ 0,25 l/s S ≤ 0,33 l/s B ≤ 0,42 l/s C ≤ 0,50 l/s D ≤ 0,63 l/s for example IA IIC / B ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Dynamic pressure (0,1 to 0,5) MPa [(1,0 to 5,0) bar] Group I - Group II – unclassified I /- a II /- a ≤ 65 °C Without flow rate class: mechanical mixing valves without interchangeable outlet accessories are tested with the original outlet accessories of the manufacturer and are not marked with a flow rate class Mechanical mixing valves for use at pressures lower than those in Table are covered by EN 1286 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) 12.2 Mechanical endurance of diverters 12.2.1 General This clause describes two methods, one for manual diverters and one for diverters with automatic return that shall be carried out to evaluate the mechanical endurance of diverters of mechanical mixing valves, and specifies the test criteria 12.2.2 Test method 12.2.2.1 Principle The diverter is subjected to a specified number of operations whilst being supplied alternately with cold water and with hot water to test its behaviour over a period of time, taking into account the effect of water temperature 12.2.2.2 Apparatus For manual diverter, an automatic machine that ensures alternate operations at the rate of (15 −01 ) cycles per minute and supply circuits with a pump or similar device to supply the required cold water static pressure at a temperature of ≤ 30 °C and the required hot water static pressure at a temperature of (65 ± 2) °C For diverter with automatic return, a mechanism for moving the diverter to the shower position under the conditions specified in 8.6 and supply circuits identical to those specified above with, in addition, an automatic quick-acting valve to cut off the supply to the mixing valve under test 12.2.3 Procedure For manual diverter: a) install the mixing valve, as supplied, on the test rig and connect both inlets to both supply circuits; b) connect the drive device to the diverter operating member by means of a flexible component; c) adjust the static water pressure of both hot and cold circuits to (0,4 ± 0,05) MPa [(4 ± 0,5) bar]; d) in the flow-to-bath and flow-to-shower mode, adjust the flow rate to (6 ± 1) l/min by restricting the outlet; e) subject the diverter to a test of 30 000 cycles, each comprising a return movement between the extreme positions; throughout the test, supply the mixing valve alternately at both inlets with cold water for (15 ± 1) min, then hot water for (15 ± 1) For diverter with automatic return: a) install the mixing valve, as supplied, on the test rig and connect both inlets to both supply circuits; b) connect the drive device to the diverter operating member by means of a flexible component; c) adjust the static pressure of both hot and cold circuits to (0,4 ± 0,05) MPa [(4 ± 0,5) bar]; d) in the flow-to-bath and flow-to-shower mode, adjust the flow rate to (6 ± 1) l/min by restricting the outlet; e) subject the diverter to a test of 30 000 cycles, one cycle being defined as follows: 38 1) with the diverter in the “flow to bath” position, allow water to flow through the spout for (5 ± 0,5) s; 2) move the diverter to the shower position; 3) allow water to flow through the shower outlet for (5 ± 0,5) s; Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) 4) use the quick-acting valve to cut off the supply to the mixing valve, allowing the diverter to return to the “flow to bath” position, and then reopen the supply Throughout the test, supply the mixing valve alternately at both inlets with cold water for (15 ± 1) and then hot water for (15 ± 1) 12.2.4 Requirements Throughout the test, there shall be no incidents of leaks, failure of diverter to reset, blockage, etc On completion of 30 000 cycles, the assembly shall be leaktight when tested according to 8.5 for manual diverters or 8.6 for diverters with automatic return Table 13 — Summary of test conditions for diverters Field of application Conditions Supply system Pressure of: (0,4 + 0,05) MPa Cold and hot water [(4,0 + 0,5) bar] Cold water temperature ≤ 30 °C Hot water temperature (65 ± 2) °C Timing of supply: Cold or hot water Time of flow: to bath or to shower outlet (15 ± 1) (5 ± 0,5) s Flow rate to bath and to (6 ± 1) l/min shower outlet Operation rate for manual diverters (cycles) (15 ± 1) -1 Backflow prevention See Clause 13 Number of cycles 30 000 39 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) 12.3 Mechanical endurance of swivel spouts 12.3.1 General This clause describes a method that shall be carried out to test the mechanical endurance of swivel spouts of mixing valves and specifies the corresponding test criteria 12.3.2 Test method 12.3.2.1 Principle The principle of the test is to reciprocate the spout of the mixing valve with both inlets fed with cold water for a specified number of cycles in order to test its behaviour over a period of time 12.3.2.2 Apparatus  Automatic machine, capable of swivelling the spout as described in 12.3.3 and 12.3.4 at a rate of (15 ± 1) cycles per minute;  cold water supply circuit with water at a temperature of ≤ 30 ˚C with a pump or a similar device, for supplying the required pressure;  mass of (1 ± 0,1) kg if the spout is ≤ 200 mm , or sufficient to apply a bending moment of (2 ± 0,25) Nm if the spout is > 200 mm 12.3.3 Procedure a) Mount the mixing valve on the machine and connect the inlet(s) to the supply circuit; b) with the mixing valve closed, adjust the static water pressure to (0,4 ± 0,05) MPa [(4 ± 0,5) bar]; c) open the mixing valve fully and adjust the flow rate to (6 ± 1) l/min by restricting the nozzle outlet; d) subject the spout to a test of 80 000 cycles, each cycle comprising a movement of the spout through an arc of 120° in both directions or, if there is a stop, over 90 % of the available travel 12.3.4 Requirements During the test there shall be:  no deformation or fracture of the swivel spout;  no deformation or fracture of the device connecting the spout to the body;  no leakage of the assembly At the end of the test, the spout shall be leaktight under the conditions given in 8.4 40 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) 13 Backflow protection Backflow protection shall be provided using appropriate devices referenced in EN 1717 14 Acoustic characteristics 14.1 General This clause specifies the test method that shall be carried out to classify mixing valves by acoustic group and, in appropriate cases, by flow class NOTE required The use of mechanical mixing valve without acoustical group I or II is not precluded where no acoustical group is 14.2 Procedure The method of measurement shall be in accordance with EN ISO 3822-1 under the conditions specified in EN ISO 3822-2 14.3 Requirements 14.3.1 Flow rate class of mechanical mixing valves Mechanical mixing valves with provision for connecting interchangeable outlet accessories such as flow rate regulators, shower, flow straightener, etc having been tested with a low-noise flow resistance in accordance with EN ISO 3822-4 are allocated a corresponding flow class as shown in 14.3.2 Flow rate class of mixing valves without provision for connecting accessories Mechanical mixing valves without provision for connecting interchangeable outlet accessories or water saving accessories are tested as supplied and the flow rate obtained at the test pressure of (0,3 ± 0,02) MPa [(3,0 ± 0,2) bar] is reported 14.3.3 Correspondence between flow rate classes and measurements Hydraulic resistances are defined in classes (EN ISO 3822-4) as a function of their calibrated flow rate at (0,3 ± 0,02) MPa [(3,0 ± 0,2) bar] (see 0; see also EN 246) Table 14 — Flow rate classes (EN ISO 3822-4:1997, Annex A) Flow rate Flow rate class (l/s) Z 0,15 A 0,25 S 0,33 B 0,42 C 0,50 D 0,63 41 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) 14.3.4 Expression of results The results of the measurements taken in accordance with EN ISO 3822-1 shall be expressed by the noise emission of the tapware Lap in dB(A) 14.3.5 Determination of acoustic group The acoustic group is determined by the value of Lap obtained at a flow pressure of 0,3 MPa (3 bar) The mixing valve is classified in acoustic group I, II or U as shown in Table 15 — Acoustic group 42 Group Lap in dB(A) I ≤ 20 II 20 < Lap ≤ 30 U (unclassified) > 30 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) Annex A (normative) Apparatus A.1 Apparatus This comprises:  two supply circuits (hot water and cold water) (Figure A.1);  one test circuit (Figure A.2) A.1.1 Supply circuits Key pressure regulator piping flow rate measurement cold water hot water sample under test Figure A.1 — Supply circuits 43 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) Each circuit comprises: a) a temperature regulating device (not shown) for adjusting: 1) the temperature of the cold water to a value of (10 to 15) °C; 2) the temperature of the hot water to a value between (60 to 65) °C; b) a device (1) for obtaining the required pressures; c) piping (2) of appropriate cross-section for the flow to be obtained; d) a device (3) for measuring the flow rate A.1.2 Test circuit Each hot water or cold water supply to the mixing valve comprises: a) piping made from a rigid metal tube of diameter and length in accordance with the dimensions in Table A.1 and Figure A.2 comprising: 1) a device for connecting this piping to the supply circuit; 2) a pressure take off tee; 3) a temperature probe; 4) a connection to the reinforced flexible pipe; b) a reinforced flexible pipe, 500 mm long, of minimum internal diameter equal to that of the metal tube, with a device at the end for connection to the mixing valve; c) a temperature probe for measuring the temperature of the water at the mixing valve outlet; d) a device without backlash for automatic or non-automatic operation at a rate of approximately 0,5 °angular/s or mm/s of the temperature and flow rate control device(s) of the mixing valve; e) equipment for measuring: 1) pressures (measurement accuracy ± % of the measured values); 2) flow rates (measurement accuracy ± % of the measured values); 3) temperatures (measurement accuracy ± K of the measured values); 4) movement (measurement accuracy of ± 0,5 mm or ± 0,5° angular of the measured values) NOTE The various parameters QC, QH, QM and G may be recorded continuously where QC is the flow of cold water; QH is the flow of hot water; QM is the flow of mixed water 44 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) Table A.1 — Connecting dimension Connecting dimension mixing valve of the Internal mm diameter Union nut ½ 13 Gẵ ắ 20 Gắ Dimensions in millimetres Key connection to supply circuit metal tube pressure tapping temperature probe connection hot water mixed water temperature probe cold water Figure A.2 — Test circuit A.1.3 Pressure take off tees Pressure take off tees shall be of the individual pressure tapping type or the annular slit type (see Annex B) 45 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) A.2 Mounting of the mixing valve Depending on the type of mixing valve, one of the following mounting arrangements shall be used: Key flexible tube Figure A.3 — Mounting of the mixing valve 46 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) Annex B (informative) Pressure take-off tee Dimensions in millimetres Key hex or spanner flats both ends conforming to type A, EN 1254-2 NOTE Unspecified tolerances are ± Figure B.1 — Pressure take-off tee Table B.1 — Dimensions of the pressure take-off tee Dimensions of the pressure take off tee Nominal size of tap A B C E F max max max ½ 15,25 15,15 26 25 13,95 13,80 40 ¾ 22,30 22,20 36 35 20,75 20,50 50 J K Screws M L max Max 37 0,7 0,6 19 18 5,5 47 0,8 0,6 26 25 9,0 No Size M4 x 15 47 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) Figure B.2— Schematic examples of pressure take-off tees 48 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) Recommendation for the design of pressure take-off tees: Figure B.2 shows three examples of pressure take-off tees giving equivalent results: a) individual: types A and B; b) annular slit: type C Requirements relating to the design and manufacture of pressure take-off tees are given in EN ISO 5167-1 The main principles are: a) b) Individual type: 1) The axis of the pressure orifices shall intersect the axis of the piping (or the casing) and be perpendicular to it; the opening of the orifice shall be circular and the edges flush with the wall of the piping (or the casing) with an angle as sharp as possible Slight rounding at entry is permitted (radius ≤ 1/10 diameter of the pressure orifice) 2) The diameter of the pressure orifice shall be less than 0,1 D (D; internal diameter of the tube or casing) 3) There shall be an even number (at least 4) of the pressure orifices The angles formed by the arcs of the pressure orifices shall be approximately equal 4) The area of the free cross section of the annular chamber of the casing shall be greater than or equal to the half total area of the orifices connecting the chamber to the piping Annular slit: 1) The thickness f of the annular slit shall be equal to or greater than twice the width i of the slit 2) The area of the free section of the annular chamber should be equal to or greater than half the total area of the annular slit connecting the chamber to the piping 3) All surfaces coming into contact with the fluid measured shall be clean and well finished 4) The width of the annular slit shall be nominally mm 49 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 EN 817:2008 (E) Bibliography [1] EN 1254-2, Copper and copper alloys — Plumbing fittings — Part 2: Fittings with compression ends for use with copper tubes [2] EN 1286, Sanitary tapware — Low pressure mechanical mixing valves — General technical specification [3] EN ISO 5167-1:2003, Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full — Part 1: General principles and requirements (ISO 51671:2003) 50 Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 This page has been intentionally left blank Licensed copy: The University of Hong Kong, The University of Hong Kong, Version correct as of 18/04/2009 01:54, (c) BSI BS EN 817:2008 BSI Group Headquarters 389 Chiswick High Road, London, W4 4AL, UK Tel +44 (0)20 8996 9001 Fax +44 (0)20 8996 7001 www.bsigroup.com/ standards BSI - British Standards Institution BSI is the independent national body responsible for preparing 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