1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 13971:2012Refrigeration systems and heat pumps Flexible pipe elements, vibration isolators, expansion joints and non-metallic tubes Requirements and classificationBS ISO 1
2、3971:2012 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 13971:2012. The UK participation in its preparation was entrusted to TechnicalCommittee RHE/18, Refrigeration safety.A list of organizations represented on this committee can beobtained on request to its
3、 secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2012. Published by BSI StandardsLimited 2012 ISBN 978 0 580 72055 0 ICS 27.080; 27.200 Compliance with a British Stan
4、dard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 30 September 2012. Amendments issued since publicationDate Text affectedBS ISO 13971:2012 ISO 2012Refrigeration systems and heat pumps Flexible p
5、ipe elements, vibration isolators, expansion joints and non-metallic tubes Requirements and classificationSystmes de rfrigration et pompes chaleur lments flexibles de tuyauterie, isolateurs de vibration, joints de dilatation et tubes non mtalliques Exigences et classificationINTERNATIONAL STANDARDIS
6、O13971First edition2012-09-01Reference numberISO 13971:2012(E)BS ISO 13971:2012ISO 13971:2012(E)ii ISO 2012 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
7、electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.o
8、rgWeb www.iso.orgPublished in SwitzerlandBS ISO 13971:2012ISO 13971:2012(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO te
9、chnical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates close
10、ly with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.The main task of technical committees is to prepare International Standards. Draft I
11、nternational Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.Attention is drawn to the possibility that some of the elements of this document
12、may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.ISO 13971 was prepared by Technical Committee ISO/TC 86, Refrigeration and air-conditioning, Subcommittee SC 1, Safety and environmental requirements for refrigerating systems. ISO 20
13、12 All rights reserved iiiBS ISO 13971:2012ISO 13971:2012(E)IntroductionFlexible pipe elements are used to eliminate impermissible stresses from refrigerating circuits and absorb pipe expansion or relative movements of components.Flexible pipe elements are often the weakest part of a refrigerating s
14、ystem and the part most likely to suffer from fatigue or stress corrosion cracking.iv ISO 2012 All rights reservedBS ISO 13971:2012Refrigeration systems and heat pumps Flexible pipe elements, vibration isolators, expansion joints and non-metallic tubes Requirements and classification1 ScopeThis Inte
15、rnational standard describes requirements, design and installation of flexible pipe elements (e.g., metallic flexible pipe, metallic flexible tube, vibration isolator, expansion joint) and non-metallic tube used in the refrigerant circuits of refrigerating systems and heat pumps.It also describes th
16、e requirements to qualify the tightness and permeability of non-metallic tubes (e.g., plastic) used in evaporating and/or condensing sides of refrigerating systems and heat pumps.This International standard does not apply to flexible pipes that are only occasionally stressed beyond the elastic limit
17、 (e.g., during repair work), or to joints that are free to rotate or hinge.2 Normative referencesThe 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 referenc
18、ed document (including any amendments) applies.ISO 175, Plastics Methods of test for the determination of the effects of immersion in liquid chemicalsISO 5149-2, Refrigerating systems and heat pumps Safety and environmental requirements Part 2: Design, construction, testing, marking and documentatio
19、nISO 6605:2002, Hydraulic fluid power Hoses and hose assemblies Test methods3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.3.1expansion jointtubular pipe element shaped in such a way that it provides limited movement to accommodate thermal expansi
20、on without reaching its elastic limit3.2flexible pipe elementpipe or tube of non-permanent shape linking two parts that are moveable with respect to each otherSee Figure 1.NOTE 1 This generic term includes all types, as defined in 3.1, 3.3 to 3.5, and 3.8 to 3.11.NOTE 2 Flexible pipe elements may in
21、clude a plastic barrier in the construction, either as a liner on the inner surface or as a sandwich in the pipe wall. The main purpose of such a barrier is to reduce the permeation of refrigerant gas.NOTE 3 This type of pipe is flexible by virtue of the shape into which the tube is bent (e. g., coi
22、led capillary tube).3.3flexible pipe element, fixed installedelement used to minimize assembly difficulty by accommodating slight misalignments or relative movement between components of the refrigerating systemINTERNATIONAL STANDARD ISO 13971:2012(E) ISO 2012 All rights reserved 1BS ISO 13971:2012I
23、SO 13971:2012(E)3.4flexible pipe element, for intermittent movementelement moving intermittently to take up relative movement between components of the refrigerating system3.5flexible pipe element, for significant movementelement moving regularly through significant distance to allow the operation o
24、f refrigerating equipmentEXAMPLE Plate freezers.3.6maximum allowable pressurePSmaximum pressure for which the equipment is designed, as specified by the manufacturer3.7maximum/minimum allowable temperatureTSmaximum/minimum temperature for which the equipment is designed, as specified by the manufact
25、urer3.8metallic flexible pipereadily flexible, small bore pipe, that is capable of movement within its elastic limit during operation of the refrigerating system or within reasonable plastic deformation range during installation or maintenance3.9metallic flexible tubetubular flexible element designe
26、d to bend within defined limits and containing a corrugated metal bellows, the corrugations of which may be annular or spiralSee Figure 1.NOTE 1 Metallic flexible tubes can be reinforced by metallic braiding covered either by rubber or plastic but the whole element should be designed so that, when b
27、ent within pre-determined limits, it is not stressed beyond the elastic limit.NOTE 2 This type of pipe is flexible by virtue of its design and construction, e. g. bellows.3.10non-metallic flexible tubetubular flexible element designed to bend within defined limitsSee Figure 1.NOTE 1 Non-metallic fle
28、xible tubes can have smooth bore or corrugated bore and be reinforced to withstand pressure, vacuum or external impact.NOTE 2 This type of pipe is flexible by virtue of its material (e. g., elastomer).NOTE 3 Non-metallic flexible tube is intended to include all pipes made of plastic or rubber, mono-
29、layer or multi-layer, reinforced or non-reinforced.3.11vibration isolatorshort, flexible tube usually of metallic construction, that is intended to reduce the effects of vibration from the compressor to other parts of the refrigerating system or vice versa2 ISO 2012 All rights reservedBS ISO 13971:2
30、012ISO 13971:2012(E)Flexible pipe elementsmetallic flexible pipe (3.8)metallic flexible tube (3.9)non-metallic flexible tube (3.10)flexibility is configuration dependent(e.g. coils)flexibility is construction dependent(e.g. bellows)flexibility is material dependent(e.g. elastomer)Figure 1 Types of f
31、lexible pipe elements4 Applications4.1 General4.1.1 The refrigerating system shall be so designed and constructed that the components being connected by the flexible pipe elements and non-metallic tubes cannot move in such a way as to stress the pipe element beyond its fatigue limit during operation
32、, including start and stop.4.1.2 Flexible pipe elements and non-metallic tubes shall be installed in accordance with the manufacturers instructions.4.1.3 Flexible pipe elements, vibration isolators, expansion joints and non-metallic tubes shall be used only if necessary.4.2 Flexible pipe elements fo
33、r significant movements, flexible pipe elements for intermittentmovement and fixed installed flexible pipe elementsFlexible pipe elements for significant movements, flexible pipe elements for intermittent movement and fixed installed flexible pipe elements shall be supported and connected in such a
34、way that they are not bent to radii less than those specified by the manufacturer; not allow the generation of static electricity when non-conducting refrigerants pass through them at high velocity;NOTE This can be achieved by the use of antistatic plastic as lining. be so constructed and connected
35、that they are not liable to damage by the freezing of water or by corrosion by humidity at the surface or at joints.Flexible pipe elements for significant movement and flexible pipe elements for intermittent movement shall be so installed that there is no danger of the outer covering being abraded o
36、n stationary objects during movement of the flexible pipe.The manufacturer of non-metallic flexible tubes for significant movements shall specify the permeability of the pipe element to water vapour and to the refrigerants for which it is suitable (see Clauses 7 and 8). ISO 2012 All rights reserved
37、3BS ISO 13971:2012ISO 13971:2012(E)4.3 Vibration isolators4.3.1 Vibration isolators shall be so installed that they are not subjected to combined bending and twisting.4.3.2 Vibration isolators shall be so installed that they can accommodate not only the vibration emanating from a running compressor
38、but also the movement of a spring-mounted compressor at starting and stopping.4.3.3 Where the vibration being isolated has components in more than one plane, care shall be taken to ensure that the axis of the vibration isolator enables accommodation of all these components. If necessary, two vibrati
39、on isolators connected at right angles to each other shall be installed.4.3.4 Vibration isolators shall be firmly anchored at the point where they join the fixed piping of the refrigerating system.4.3.5 Vibration isolators shall be so constructed and connected that they are not liable to damage by f
40、reezing of water at the surface or at joints. In particular, they shall not be installed vertically, unless a waterproof sleeve has been tightly fitted over the isolator where the freezing of water is expected.4.3.6 Vibration isolators shall be installed in accordance with the manufacturers instruct
41、ions.NOTE 1 Vibration isolators are commonly used as suction and discharge connections for compressors and are also sometimes used as connections to evaporators and condensers.NOTE 2 Vibration isolators are not suitable for preventing the transmission of gas pulsation.4.4 Expansion joints4.4.1 Expan
42、sion joints or equivalent means shall be used to protect the system if the effects of thermal expansion are significantNOTE Expansion joints are designed to take up strain produced by thermal expansion of the piping without stressing the piping system beyond its elastic limit. Expansion joints can b
43、e of the bellows type. Alternatively, flexibility can be produced by using a suitable configuration of the piping system (angular, lateral or axial compensating movements).4.4.2 In every case the unrestrained expansion of the piping system shall be calculated to indicate the degree of flexibility wh
44、ich is required.4.4.3 Where expansion joints are used, piping systems shall be designed with fixed anchor points and guide points.NOTE Anchor points, which can be a compressor or a pressure vessel or can be additional rigid fixings to a building structure, are the fixed points between which expansio
45、n and contraction occurs. Guide points are necessary to prevent uncontrolled movement of the pipe in a transverse direction.4.4.4 For insulated piping systems, the anchor points shall be fixed to the pipe but the guide points shall be on the outside of the insulation.4.4.5 Bellows type expansion joi
46、nts shall be so installed that they do not suffer from longitudinal movement produced by internal pressure.4.4.6 Bellows-type expansion joints shall not be subjected to excessive shear forces due to transverse movement of pipes.4.4.7 Care shall be taken to prevent damage to bellows by freezing of co
47、ndensed water within the convolutions of the bellows. This may be achieved by packing the convolutions with low temperature grease or paste. Insulation and vapour seal should be applied over the paste.4 ISO 2012 All rights reservedBS ISO 13971:2012ISO 13971:2012(E)4.4.8 Expansion joints shall be ins
48、talled in accordance with the manufacturers instructions.4.5 Metallic flexible pipes4.5.1 Metallic flexible pipes shall be of material that is resistant to work-hardening, or shall be arranged so that work-hardening does not take place.4.5.2 Metallic flexible pipe coils shall not resonate under any
49、foreseeable conditions of continuous operation. Design or choice of metallic flexible pipe shall take fatigue due to stress during starting and stopping into account.NOTE Metallic flexible pipes, which are usually of small bore, are used to prevent the transmission of vibration from the piping system to, for example, controls and safety devices. Such pipes are often bent into a spiral to minimize the stress.5 MaterialsThe materials used shall be subjected to ISO 175 for the refrigerants used and for the environment to
