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1、BRITISH STANDARD BS EN 12178:2003 Refrigerating systems and heat pumps Liquid level indicating devices Requirements, testing and marking The European Standard EN 12178:2003 has the status of a British Standard ICS 27.080; 27.200 ? Licensed Copy: sheffieldun sheffieldun, na, Sat Oct 28 07:14:40 GMT+0
2、0:00 2006, Uncontrolled Copy, (c) BSI BS EN 12178:2003 This British Standard, was published under the authority of the Standards Policy and Strategy Committee on 15 December 2003 BSI 15 December 2003 ISBN 0 580 43088 X National foreword This British Standard is the official English language version
3、of EN 12178:2003. The UK participation in its preparation was entrusted to Technical Committee RHE/18, Refrigeration safety, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards whic
4、h implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publicat
5、ion does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/
6、European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN title page
7、, pages 2 to 14, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments Licensed Copy: sheffieldun sheffieldun, na, Sat Oct 28 07:14:40 GMT+00:00 2006, Uncontrol
8、led Copy, (c) BSI EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 12178 December 2003 ICS 27.080; 27.200 English version Refrigerating systems and heat pumps - Liquid level indicating devices - Requirements, testing and marking Systmes de rfrigration et pompes chaleur - Indicateurs de liquide -
9、 Exigences, essais et marquage Klteanlagen und Wrmepumpen - Flssigkeitsstandanzeiger - Anforderungen, Prfung und Kennzeichnung This European Standard was approved by CEN on 3 November 2003. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for g
10、iving 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 Management Centre or to any CEN member. This European Standard exists in three official vers
11、ions (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 Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Cz
12、ech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG M
13、anagement Centre: rue de Stassart, 36 B-1050 Brussels 2003 CENAll rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 12178:2003 E Licensed Copy: sheffieldun sheffieldun, na, Sat Oct 28 07:14:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 12
14、178:2003 (E) 2 Contents page Foreword3 1Scope 4 2Normative references 4 3Terms and definitions5 4List of Symbols 6 5General requirements6 6Materials7 7Design.8 8Fitting requirements 10 9Testing 10 10Application10 11Marking and additional information.11 12Documentation.11 Annex ZA (informative) Relat
15、ionship between this European Standard and the Essential Requirements of EU Directive 97/23/EC .13 Bibliography14 Licensed Copy: sheffieldun sheffieldun, na, Sat Oct 28 07:14:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 12178:2003 (E) 3 Foreword This document (EN 12178:2003) has been prepared by
16、 CEN/TC 182, “Refrigerating systems, safety and environmental requirements“, the secretariat of which is held by DIN. 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 June 2004, and conflicting nat
17、ional standards shall be withdrawn at the latest by June 2004. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive(s). For relationship with EU Directive(s), see informati
18、ve annex ZA, which is an integral part of this document. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary
19、, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Licensed Copy: sheffieldun sheffieldun, na, Sat Oct 28 07:14:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 12178:2003 (E) 4 1 Scope This European Standard spec
20、ifies safety requirements, safety factors, test methods, test pressures and marking of liquid level indicating devices, referred to throughout this standard as “level indicators“, for use in refrigerating systems and heat pumps. It applies to devices connected to refrigerant vessels (e.g. on high-pr
21、essure liquid receivers, intercoolers and low- pressure separators) and to devices connected to other parts of a refrigerating system (e.g. oil-level sight glasses on a compressor). This European Standard applies to those types of level indicators that are direct and indirect reading devices (e.g. s
22、ight glasses, frosting tubes), and includes electrical and pneumatic indicators. This European Standard describes the procedure to be followed when designing (by calculation or by an experimental design method) level indicator parts subjected to pressure as well as the criteria to be used for the se
23、lection of materials. This European Standard applies to the design of level indicators with respect to pressure containment and describes methods by which the reduced impact values at lower temperatures may be taken into account in a safe manner. It also gives guidance on some aspects of application
24、 and installation. 2 Normative references This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amen
25、dments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies (including amendments). EN 378-1, Refrigerating systems and heat pumps Safety an
26、d environmental requirements Part 1: Basic requirements, definitions, classification and selection criteria. EN 378-2, Refrigerating systems and heat pumps Safety and environmental requirements Part 2: Design, construction, testing, marking and documentation. EN 378-4, Refrigerating systems and heat
27、 pumps Safety and environmental requirements Part 4: Operation, maintenance, repair and recovery. prEN 764-1, Pressure equipment Terminology Part 1: Pressure, temperature, volume, nominal size. EN 12284:2003, Refrigerating systems and heat pumps Valves Requirements, testing and marking. EN 60529, De
28、grees of protection provided by enclosures (IP code) (IEC 60529:1989). EN ISO 6708:1995, Pipework components Definition and selection of DN nominal size (ISO 6708:1995). ISO 7268, Pipe components - Definition of nominal pressure. Licensed Copy: sheffieldun sheffieldun, na, Sat Oct 28 07:14:40 GMT+00
29、:00 2006, Uncontrolled Copy, (c) BSI EN 12178:2003 (E) 5 3 Terms and definitions For the purposes of this European Standard, the terms and definitions given in EN 378-1 and prEN 764-1 and the following apply. 3.1 min t0 100 lowest temperature at which pressurized parts can be used at a load of up to
30、 100 % of the allowable design stress at 20 C, taking the safety factors according to Table A.2 of EN 12284:2003 into account 3.2 min t0 75 lowest temperature at which pressurized parts can be used, if its load amounts to 75 % maximum of the allowable design stress at 20 C, taking the safety factors
31、 according to Table A.2 of EN 12284:2003 into account 3.3 min t0 25 lowest temperature at which pressurized parts can be used, if their load amounts to 25 % maximum of the allowable design stress at 20 C, taking the safety factors according to Table A.2 of EN 12284:2003 into account 3.4 self-closing
32、 balls self-closing shut-off arrangement NOTEThe arrangement comprises balls positioned in the connecting channel close to the sight glass in such a manner that the balls will not be affected at low flow rates. At high flow rates the balls will be carried forward with the flow and block the connecti
33、ons to the sight glass. 3.5 reflex glass glasses having prismatic flutes on the inside, which will break up the incoming light NOTEThe liquid zone will absorb the light and will correspondingly appear dark. The gas/vapour zone will reflect the light and will correspondingly appear bright. 3.6 direct
34、 reading level indicator level indicator where it is possible to see the liquid level 3.7 indirect reading level indicator level indicator where the liquid level is not visible NOTEThe level is indicated by auxiliary means; electrically, magnetically or by observing the frost on a tube. 3.8 self-con
35、tained unit level indicator which is assembled and tested by the manufacturer 3.9 add-on unit level indicator delivered in parts from the manufacturer for mounting directly onto the system and which can only be tested after assembly and connection on site 3.10 level indicator with magnetically opera
36、ted indication device which transfers the measured value at any particular moment to an indicating device by means of a float with a built-in permanent magnet system 3.11 sight glass direct reading level indicator consisting of a glass plate and holder to enable viewing of the liquid surface License
37、d Copy: sheffieldun sheffieldun, na, Sat Oct 28 07:14:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 12178:2003 (E) 6 NOTEThe shape of the glass plate can be either circular or oblong. The glass can be smooth or provided with flutes to break up incoming light which will make the liquid-filled part
38、 darker than the vapour-filled part. A sight glass can be a self- contained or add-on unit. 3.12 frosting tube device, the principle of which is based on the frosting of the humidity of the surrounding air, and which consists of a corrosion protected tube arranged vertically outside the vessel and c
39、onnected to the vessel at top and bottom. It is especially suitable for refrigerant temperatures below 3 C and ambient temperature above freezing point. The top level of the frosting on the tube will indicate the liquid level in the vessel 3.13 auxiliary powered level indicator device which operates
40、 electrically or pneumatically to indicate the level by means such as the following: a) differential pressure transducer; b) capacitative transducer; c) inductive transducer; d) ultrasonic transducer; e) displacement principle with a displacement float. 3.14 operating range temperature and pressure
41、conditions at which the liquid level can be safely operated 3.15 nominal size DN alpha-numeric designation of size for components of a pipework system see EN ISO 6708:1995 3.16 Nominal pressure (PN) value of a pressure in the range of the maximum allowable pressure for planning a plant or a componen
42、t see ISO 7268 4 List of Symbols For symbols see EN 12284:2003, clause 4 (Table 1). 5 General requirements 5.1 Installation and operation Level indicators shall be designed for installation and operation in accordance with EN 378-1, EN 378-2 and EN 378-4. 5.2 Components under pressure All parts of t
43、he level indicator shall be designed and manufactured to remain leakproof and withstand the pressures which may occur during operation, standstill and transportation, taking into account the thermal, physical and chemical stresses to be expected. Licensed Copy: sheffieldun sheffieldun, na, Sat Oct 2
44、8 07:14:40 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 12178:2003 (E) 7 5.3 Excessive mechanical stress After installation, level indicators, especially in systems where hot gas defrosting is used, shall not be under excessive mechanical stress from fitting of the pipe or from temperature variatio
45、ns during operation. NOTEHot gas defrosting can produce hydraulic shocks resulting in transient pressures in excess of PS. Further information can be obtained from EN 378 (all Parts). 5.4 Leakage See 5.4 of EN 12284:2003. 6 Materials 6.1 Material properties Materials, including welding filler metals
46、, solders, braze, sealant and glass, shall allow for the thermal, chemical and mechanical stresses arising in system operation. The material shall be resistant to the refrigerants, solvents (in absorption systems) and refrigerant-oil mixtures used in each particular case. 6.2 New materials New mater
47、ials shall be tested in accordance with annex A to annex D of EN 12284:2003. 6.3 Using non-metallic materials See 6.1.2 of EN 12284:2003. 6.4 Requirements for materials to be used for pressurized parts See 6.2 of EN 12284:2003. 6.5 Compatibility of connections Materials, which are to be physically l
48、inked, shall be suitable for an effective connection, depending on the particular materials used and on the dimensions of piping specified. 6.6 Ductility Materials which are to be considerably deformed shall be sufficiently ductile and capable of being heat treated where necessary. 6.7 Brittle fract
49、ure Level indicators shall be designed and constructed so that they are not subject to brittle fraction at the minimum operating temperature (min to) using the method specified in annex D of EN 12284: 2003. 6.8 Ageing Materials for pressurized parts shall not be significantly affected by ageing. 6.9 Castings Castings shall exhibit a low residual stress level. If they are not subjected to stress relief heat treatment, controlled cooling shall be ensured after the c