prEN ISO 13971
(Main)Refrigeration systems and heat pumps - Flexible pipe elements, vibration isolators, expansion joints and non-metallic tubes - Requirements and classification (ISO 13971:2012)
Refrigeration systems and heat pumps - Flexible pipe elements, vibration isolators, expansion joints and non-metallic tubes - Requirements and classification (ISO 13971:2012)
This International 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 the 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 (e.g., during repair work), or to joints that are free to rotate or hinge.
Kälteanlagen und Wärmepumpen - Flexible Rohrleitungsteile, Schwingungsabsorber, Kompensatoren und Nichtmetall-Schläuche - Anforderungen und Klassifikation (ISO 13971:2012)
Systèmes de réfrigération et pompes à chaleur - Éléments flexibles de tuyauterie, isolateurs de vibration, joints de dilatation et tubes non métalliques - Exigences et classification (ISO 13971:2012)
Hladilni sistemi in toplotne črpalke - Gibki cevni elementi, blažilniki vibracij, raztezni spoji in nekovinske cevi - Zahteve in klasifikacija (ISO 13971:2012)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-julij-2025
Hladilni sistemi in toplotne črpalke - Gibki cevni elementi, blažilniki vibracij,
raztezni spoji in nekovinske cevi - Zahteve in klasifikacija (ISO 13971:2012)
Refrigeration systems and heat pumps - Flexible pipe elements, vibration isolators,
expansion joints and non-metallic tubes - Requirements and classification (ISO
13971:2012)
Kälteanlagen und Wärmepumpen - Flexible Rohrleitungsteile, Schwingungsabsorber,
Kompensatoren und Nichtmetall-Schläuche - Anforderungen und Klassifikation (ISO
13971:2012)
Systèmes de réfrigération et pompes à chaleur - Éléments flexibles de tuyauterie,
isolateurs de vibration, joints de dilatation et tubes non métalliques - Exigences et
classification (ISO 13971:2012)
Ta slovenski standard je istoveten z: prEN ISO 13971
ICS:
27.080 Toplotne črpalke Heat pumps
27.200 Hladilna tehnologija Refrigerating technology
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
INTERNATIONAL ISO
STANDARD 13971
First edition
2012-09-01
Refrigeration systems and heat pumps —
Flexible pipe elements, vibration
isolators, expansion joints and non-
metallic tubes — Requirements and
classification
Systèmes de réfrigération et pompes à chaleur — Éléments flexibles
de tuyauterie, isolateurs de vibration, joints de dilatation et tubes non
métalliques — Exigences et classification
Reference number
ISO 13971:2012(E)
©
ISO 2012
ISO 13971:2012(E)
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Published in Switzerland
ii © ISO 2012 – All rights reserved
ISO 13971:2012(E)
Foreword
ISO (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
technical 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 closely 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 International 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 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 13971:2012(E)
Introduction
Flexible 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 system and the part most likely to suffer
from fatigue or stress corrosion cracking.
iv © ISO 2012 – All rights reserved
INTERNATIONAL STANDARD ISO 13971:2012(E)
Refrigeration systems and heat pumps — Flexible pipe
elements, vibration isolators, expansion joints and non-metallic
tubes — Requirements and classification
1 Scope
This International 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 the 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 (e.g., during repair work), or to joints that are free to rotate or hinge.
2 Normative references
The 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 referenced document
(including any amendments) applies.
ISO 175, Plastics — Methods of test for the determination of the effects of immersion in liquid chemicals
ISO 5149-2, Refrigerating systems and heat pumps — Safety and environmental requirements — Part 2:
Design, construction, testing, marking and documentation
ISO 6605:2002, Hydraulic fluid power — Hoses and hose assemblies — Test methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
expansion joint
tubular pipe element shaped in such a way that it provides limited movement to accommodate thermal expansion
without reaching its elastic limit
3.2
flexible pipe element
pipe or tube of non-permanent shape linking two parts that are moveable with respect to each other
See 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 include 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., coiled capillary tube).
3.3
flexible pipe element, fixed installed
element used to minimize assembly difficulty by accommodating slight misalignments or relative movement
between components of the refrigerating system
ISO 13971:2012(E)
3.4
flexible pipe element, for intermittent movement
element moving intermittently to take up relative movement between components of the refrigerating system
3.5
flexible pipe element, for significant movement
element moving regularly through significant distance to allow the operation of refrigerating equipment
EXAMPLE Plate freezers.
3.6
maximum allowable pressure
P
S
maximum pressure for which the equipment is designed, as specified by the manufacturer
3.7
maximum/minimum allowable temperature
T
S
maximum/minimum temperature for which the equipment is designed, as specified by the manufacturer
3.8
metallic flexible pipe
readily 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 maintenance
3.9
metallic flexible tube
tubular flexible element designed to bend within defined limits and containing a corrugated metal bellows, the
corrugations of which may be annular or spiral
See 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 bent 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.
3.10
non-metallic flexible tube
tubular flexible element designed to bend within defined limits
See Figure 1.
NOTE 1 Non-metallic flexible 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-layer or multi-layer,
reinforced or non-reinforced.
3.11
vibration isolator
short, 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 versa
2 © ISO 2012 – All rights reserved
ISO 13971:2012(E)
Flexible pipe elements
metallic flexible pipe metallic flexible tube
non-metallic flexible tube
(3.8)
(3.9)
(3.10)
flexibility is flexibility is flexibility is
configuration dependent construction dependent material dependent
(e.g. coils) (e.g. bellows) (e.g. elastomer)
Figure 1 — Types of flexible pipe elements
4 Applications
4.1 General
4.1.1 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, including start and stop.
4.1.2 Flexible pipe elements and non-metallic tubes shall be installed in accordance with the manufacturer’s
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 for significant movements, flexible pipe elements for intermittent
movement and fixed installed flexible pipe elements
Flexible 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 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 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 on 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 13971:2012(E)
4.3 Vibration isolators
4.3.1 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 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
vibration 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 freezing
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 manufacturer’s instructions.
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 joints
4.4.1 Expansion joints or equivalent means shall be used to protect the system if the effects of thermal
expansion are significant
NOTE 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 be 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 which 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 expansion 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 joints 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 condensed 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 reserved
ISO 13971:2012(E)
4.4.8 Expansi
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