ISO/TR 17784:2003

Rubber and plastics hoses and hose assemblies — Guide for use by purchasers, assemblers, installers and operating personnel

ISO/TR 17784:2003 contains general information on rubber and plastic hoses with regard to both their properties and their practical application. This includes, amongst other things, the properties of materials used in hoses, the precautions to be taken when storing hoses and the care required when installing and fitting hoses and their couplings. Safety measures when testing hoses are also indicated. This Technical Report is intended for use by system designers, purchasers, assemblers, installers and operating personnel to improve the operating safety of hoses and hose assemblies. NOTE Metal hoses are not included in this Technical Report. Attention is drawn to the following International Standards: ISO 8444, ISO 8445, ISO 8446, ISO 8447, ISO 8448, ISO 8449, ISO 8450, ISO 10807, ISO 10806 and ISO 10380. This Technical Report cannot, in practice, cover all circumstances and therefore its content is largely based on examples. It is assumed that these examples will provide sufficient information to give guidelines for a range of practical circumstances.

Tuyaux et flexibles en caoutchouc et en plastique — Guide technique à l'intention des acheteurs, des assembleurs, des installateurs et des utilisateurs

General Information

• Status: Published
• Publication Date: 10-Jul-2003
• ICS: 23.040.70 - Hoses and hose assemblies
• Technical Committee: ISO/TC 45/SC 1 - Rubber and plastics hoses and hose assemblies
• Drafting Committee: ISO/TC 45/SC 1 - Rubber and plastics hoses and hose assemblies
• Current Stage: 9093 - International Standard confirmed
• Start Date: 28-Oct-2021
• Completion Date: 12-Feb-2026

Overview

ISO/TR 17784:2003 is a Technical Report that provides practical guidance on the selection, installation, testing and safe operation of rubber and plastics hoses and hose assemblies. It is an informative, example-based resource intended to improve operating safety for system designers, purchasers, assemblers, installers and operating personnel. Metal hoses are excluded from the scope. The report complements product standards (e.g., ISO 8330) and cross‑references related ISO standards for couplings, testing and storage practice.

Key topics

• Hose selection criteria - guidance on choosing hose type based on media compatibility, temperature range, maximum/peak working pressure, operational conditions and required service life.
• Materials and construction - properties of linings, covers and reinforcements that determine pressure resistance and chemical resistance.
• Pressure fundamentals - distinctions between maximum working pressure, proof/test pressure and burst pressure; manufacturer/ user responsibilities.
• Electrical properties and static control - classifications (electrically bonded, conductive, non-conductive), design considerations for conductive wires or carbon-filled compounds, earthing/through-connection and static discharge mitigation.
• Couplings and fittings - practical notes on matching couplings to hose construction and ensuring electrical continuity where required.
• Installation and handling - avoidance of kinking, correct routing (ship-to-shore, moving equipment), use of slings and spreader bars for large-diameter hoses.
• Testing and safety - recommended safety measures for pressure testing and inspecting hose assemblies.
• Limitations - the report is illustrative and not exhaustive; recommendations are example-based and manufacturers’ instructions and product resistance lists should be consulted.

Applications and users

ISO/TR 17784 is useful for:

• System designers specifying hose assemblies for fluid transfer systems (chemical, petroleum, water, steam).
• Procurement teams and purchasers evaluating hose suitability and supplier documentation.
• Assemblers and installers responsible for coupling selection, routing and earthing.
• Operating and maintenance personnel conducting inspections, pressure tests and routine safe handling.
• Maritime and tank loading/unloading operations (guidance on ship–shore electrical insulation and hose suspension).

Practical benefits include reduced failure risk, improved static-dissipation practice, correct coupling choices and safer pressure-testing protocols.

Related standards

Relevant standards referenced in the report include:

• ISO 8330, ISO 8331 (storage), ISO 7751 (pressure ratios)
• ISO 8444, ISO 8445, ISO 8446, ISO 8447, ISO 8448, ISO 8449, ISO 8450
• ISO 10806, ISO 10807, ISO 10380
• Standards on hose cuffs and couplings: ISO 1823, ISO 2928, ISO 2929, ISO 5772

For implementation, always combine ISO/TR 17784 guidance with manufacturer data sheets and applicable product standards to ensure compliance and operational safety.

Standards Content (Sample)

TECHNICAL ISO/TR
REPORT 17784
First edition
2003-07-15
Rubber and plastics hoses and hose
assemblies — Guide for use by
purchasers, assemblers, installers and
operating personnel
Tuyaux et flexibles en caoutchouc et en plastique — Guide technique à
l'intention des acheteurs, des assembleurs, des installateurs et des
utilisateurs
Reference number
©
ISO 2003
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO 2003
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2003 — All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Terms and definitions. 1
3 General considerations for hoses. 1
4 Rubber hoses . 16
5 Plastics hoses . 23
6 Applications of rubber and plastics hoses and hose assemblies. 29
7 Couplings. 35
Bibliography . 49

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.
In exceptional circumstances, when a technical committee has collected data of a different kind from that
which is normally published as an International Standard (“state of the art”, for example), it may decide by a
simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely
informative in nature and does not have to be reviewed until the data it provides are considered to be no
longer valid or useful.
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/TR 17784 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee
SC 1, Hoses (rubber and plastics) in collaboration with the Nederlands Normalisatie-instituut (NEN). Its aim is
to promote operating security when using hoses. Technical safety, inspection, system design and fitting of
hoses are considered. This may reduce or avoid the possibility of errors when working on or with hoses.
iv © ISO 2003 — All rights reserved

Introduction
Hoses are used in places where a rigid connection to one connecting point or between two points is
impracticable or when a flexible connection is required for delivery purposes. Examples are suction and
pressure hoses, loading and discharging hoses and connections between parts of moving and vibrating
equipment. Hoses are used for carrying media which are generally under pressure in systems. Other
applications include places where the frequent linking of one or both ends of a pipe may present problems.
Users often ask hose suppliers' advice on potential uses of hoses for their applications. A hose
supplier/manufacturer can give optimum advice only if he is fully informed of the specific operating
circumstances. If insufficient information on envisaged use is obtained, incorrect advice may be given, so that
a hose not suitable for the intended use is supplied and installed. Close consultation between user and hose
manufacturer is therefore necessary. Thus, a major function of this Technical Report is to provide an
information resource to assist in decision making.
The guidelines presented in this document are derived from the Nederlands Normalisatie-instituut (NEN)
document SPE 5660 (Hoses and accessories, directives for the application), second edition 1999, and were
prepared by a task group of ISO/TC 45/SC 1/WG 4. Metal hoses, included in SPE 5660, are excluded from
this document because they fall outside the scope of ISO/TC 45/SC 1. Furthermore, the section in SPE 5660
concerning storage has been omitted as it is the subject of ISO 8331.

TECHNICAL REPORT ISO/TR 17784:2003(E)

Rubber and plastics hoses and hose assemblies — Guide for
use by purchasers, assemblers, installers and operating
personnel
1 Scope
This Technical Report contains general information on rubber and plastic hoses with regard to both their
properties and their practical application. This includes, amongst other things, the properties of materials used
in hoses, the precautions to be taken when storing hoses and the care required when installing and fitting
hoses and their couplings. Safety measures when testing hoses are also indicated. This Technical Report is
intended for use by system designers, purchasers, assemblers, installers and operating personnel to improve
the operating safety of hoses and hose assemblies.
NOTE Metal hoses are not included in this Technical Report. Attention is drawn to the following International
Standards: ISO 8444, ISO 8445, ISO 8446, ISO 8447, ISO 8448, ISO 8449, ISO 8450, ISO 10807, ISO 10806 and
ISO 10380.
This Technical Report cannot, in practice, cover all circumstances and therefore its content is largely based on
examples. It is assumed that these examples will provide sufficient information to give guidelines for a range
of practical circumstances.
2 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 8330 apply.
3 General considerations for hoses
3.1 Choosing the type of hose
3.1.1 General
When choosing the type of hose the chief criteria are:
 the resistance of the lining and cover of the hose to the media to which the hose comes into contact (air,
oil, water, steam and chemicals) and/or external influences (ozone, UV light and weathering);
 the maximum working pressure including any peak pressures;
 the minimum and maximum temperatures that may arise during operation;
 operational conditions i.e. static, dynamic, ship to shore, dragging on the ground;
 hazard category of the medium;
 required working life.
Most hose manufacturers include a “resistance list” with their hose documentation, indicating the media
against which their hose material is resistant. It should be remembered that this list refers only to the materials
used by the specific manufacturer, who will use their own composition of the product indicated by the
collective name. Temperature-pressure diagrams are also available showing the admissible pressures in
combination with certain temperatures. Although these tables are sometimes reasonably comprehensive, they
are, nonetheless, not always adequate. Hoses should not be used at temperatures outside the range advised
by the manufacturer.
The hose supplier should be notified of all requirements to which the hose needs to conform in order to make
the right choice of materials. This includes all chemical, physical and mechanical. Hoses that are not
purchased against a standard should only be used for media recommended by the manufacturer's list. The
manufacturer's advice should be obtained if there is any doubt as to the suitability of a particular hose for a
specific application.
1)
3.1.2 Maximum working pressure, proof pressure and minimum burst pressure
The hose manufacturer has information regarding maximum working pressure, test pressure and burst
pressure for hoses (see also ISO 7751 regarding the ratio of working pressure to burst pressure). The user
has information on the rated system pressure and the working pressure.
As a general rule, the hose working pressure will be selected so that it is greater than the rated pressure in the
user's system.
NOTE Pressures are sometimes divided into three classes, such as “low pressure”, “medium pressure” and “high
pressure”. However, hose manufacturers do not use these pressure categories and these terms should not be used, as
the national or international standards will not refer to them.
2)
One manufacturer may well refer to a hose with a working pressure of 10 bar as a “medium-pressure” hose
while a different manufacturer may still refer to a hose for a 200 bar pressure as a “low-pressure” hose.
The pressure-resisting strength of a hose is determined mainly by the reinforcement. The pressure-resisting
strength of tubing (a hose without reinforcement) depends on its wall thickness and material of construction.
3.2 Electrical conductivity
3.2.1 General
Hoses are divided into three types with regard to electrical conductivity, namely electrically bonded,
conductive and non-conductive (or discontinuous or insulating) hoses.
3.2.2 Design of electrically bonded hoses
Designs of electrically bonded hoses differ according to the type of hose. Electrically bonded rubber and
plastic hoses contain conducting wires (see Figure 1). These wires are always applied spirally, either
crosswise or in parallel during manufacture. The wires are connected to the metal couplings at the hose ends
in such a way that an uninterrupted pathway with low electrical resistance is obtained throughout the
assembled length when hose assemblies are coupled to each other. “Composite” or multilayer hoses (see 6.3)
have no conducting wires but are equipped with two conducting metal helixes. In this case, the two helixes
should be firmly connected to the hose coupling. Problems may arise in practice where one of the two ends of
a coated internal helix is not connected through as a result of an assembly fault. The other wire will then still
ensure a conductive connection so that the manufacturing error is not discovered when taking electrical
measurements. The non-connected internal helix may cause sparking. Coated internal helixes should
therefore be so designed that the electrical connection on both the internal and external helixes can be
checked. This may be achieved, for example, by connecting the external helix to the coupling in such a way
that it can be disconnected in order to check the electrical connection of the internal helix (to the coupling).

1) This can also be the test pressure.
2) 1 bar = 0,1 MPa.
2 © ISO 2003 — All rights reserved

Figure 1 — Hose with metal conducting wires
3.2.3 Design of conductive hoses
The construction of conductive hoses differs entirely from the designs described in 3.2.2 through the absence
of wire contacts with the couplings. The rubber composition contains a quantity of specially conductive carbon
black such that the cover of the hose is conductive. The hose couplings discharge the static electricity through
the connecting points of the installation in which the hose is fitted, or to earth. An anti-kinking spiral is often
incorporated into the hose during manufacture but it is not electrically connected to the couplings. Hoses of
this kind should be made with wire-free cuffs (see ISO 1823, ISO 2928, ISO 2929 and ISO 5772).
3.2.4 Design of non-conductive (or discontinuous or insulating) hoses
The materials used in the construction of a non-conductive hose should not be electrically conductive.
If metal materials are used within the construction, then these should not be connected to or come into contact
with the coupling.
3.3 Static electricity
3.3.1 General
The generation of static charges can be avoided by a proper choice of operating circumstances:
 adjust liquid velocities (as low as possible);
 adjust air velocities (as low as possible);
 adjust dust loading ratio on pneumatic conveyance;
 earth all conductive parts;
 speed up removal of electrical charges, e.g. by increasing the conductivity of the material being
transferred (e.g. by adding conductive additives).
NOTE 1 The removal of static electrical charge is also accelerated at high relative humidity, e.g. above 70 %.
NOTE 2 For information in connection with static electricity, see “Hazards of static electricity” (chapter 5 of document
[89] [90]
AI-25) and, if applicable, Static Electricity Guidelines, latest Edition, 1980 .
3.3.2 Earthing and through-connection
The purpose of earthing and through-connection is to reduce the mortality risk and the risk to equipment
caused by:
 faults between live conductors and non-conductive metallic parts;
 atmospheric discharge;
 accumulation of static charges.
3.3.3 Hoses for loading and unloading units
Hoses used for loading and unloading road and rail tankers can be earthed by means of an external flexible
copper cable of adequate cross-section. A spark-free make-or-break installation is desirable when linking up a
flexible earth conductor.
Examples of materials which can be conveyed by conductive or semi-conductive hoses include the following:
 petroleum distillates;
 petroleum gases;
 water or aqueous chemicals if well mixed with an oil product of low conductivity, consisting of the latter
sediments from the oil phase;
 solids (e.g. powders or granulates).
Non-conductive hoses can be used when operating conditions are safe. Examples of these conditions are:
 the charge cannot accumulate (e.g. sufficiently high specific conductivity);
 there is no explosive gas mixture;
 no static charges can be generated (e.g. low flow velocities).
NOTE The following are regarded as safe product velocities in the oil industry:
a) 1 m/s generally during the start-up period and if no data are known regarding the product;
b) 7 m/s for potentially hazardous products in pipes without micro-filter/water separator or other obstructions, following
the start-up period;
c) Unlimited, if safe conditions prevail and/or where a safe product is concerned.
3.3.4 Hoses between shore and ship
Landing platforms and tankers with loading and discharging facilities are naturally earthed by the water so that,
from the static electricity aspect, there is bound to be a good through-connection between the metal parts and
earth cables between shore and ship provide little additional protection against static. Furthermore, these
electrically conductive connections can, if not properly linked up, prove dangerous, for example, as a result of
cathodic protection installations which can cause relatively high electrical currents to flow between shore and
ship. When uncoupling the connecting pipe and/or hose connections, sparking may occur at the very point
where liquid spillages are most likely.
4 © ISO 2003 — All rights reserved

[91]
According to the IMO (International Maritime Organization) Regulations , the ship and shore installation
should be electrically insulated from each other. Means that can be used for this purpose are:
a) an insulating flange in each hose system that may be used to make a connection with the vessel; or
b) a length of conductive hose in the connection between shore and ship.
The part of the loading hose located on the shore side of the insulating equipment should be electrically
connected to the shore installation, while the hose on the ship's side should be electrically connected to the
ship.
If insulating flanges are used, only one insulating flange may be present in each line or loading arm.
If hoses are used for interconnecting shore and ship's hoses, the connection should be of the correct length
required to accommodate the maximum movement and should be electrically connected with the other lines of
the pipe system concerned.
Hoses used for loading or discharging vessels should be so suspended that kinking is avoided. Hoses with
large diameters, in particular, may not be suspended by cables. A “sling” is used for this purpose in which the
hose is laid. A sling with a hose may be transported by a hoisting device. The “sling” should meet the safety
requirements as laid down by the Shipping Inspectorate, amongst others. A so-called spreader bar may also
be used for temporary transportation of hoses.
3.4 Hose internal diameter and couplings
Although there is a relation between the nominal hose internal diameter and the actual internal diameter, the
connection between the internal diameter and the associated coupling is the most important in practice.
For hydraulic hoses, the last digit of the coupling number corresponds with the internal diameter of the hose.
The SAE nominal hose dimensions are often included in the coupling coding as -4, -6, -8, etc. (see Table 1,
column 6).
The attachment of hose to coupling can be:
 built-in;
 swaged;
 crimped;
 clamped;
 banded;
 wired-on.
 screw-on (re-usable)
NOTE See Clause 7 for end coupling connections.
Table 1 — List of internal hose diameters
Actual dimensions Comparative indications
Internal diameter
Size in accordance with USA (hydraulic)
European Britain/USA
ISO 1307 a (dash size symbol)
ISO 4397
mm mm mm inches 1/16th inch
3 3,2 3,2 3 (3,2) ⅛ -2
4 4 ± 0,4 — 4 ± 0,4 — —
5 4,8 5 5 / -3
6,3 6,4 6,3 6 ¼ -4
8 7,9 8 8 / -5
10 9,5 10 10 ⅜ -6
12,5 12,7 12,5 12 (13) ½ -8
16 15,9 16 16 ⅝ -10
19/20 19,1 19/20 20 ¾ -12
22 22,2 31,5 22 ⅞ -14
25 25,4 25 25 1 -16
31,5 31,8 31,5 32 1 ¼ -20
38/40 38,1 38/40 40 1 ½ -24
50/51 50,8 50/51 50 2 -32
63 63,5 — 60 2 ½ -40
80/76 78,6/76,2 — 75 3 -48
— 88,9 — 90 3 ½ -56
100 101,6 — 100 4 -64
125 125 ± 1,6 — — 5 —
160 150 ± 2 — — 6 —
200 200 ± 2,5 — — 8 —
250 250 ± 3 — — 10 —
315 315 ± 3 — — 12 —
NOTE Values obtained from SAE, DIN and ISO standards.
a
ISO 4397:1993, Fluid power systems and components — Connectors and associated components — Nominal outside diameters of
tubes and nominal inside diameters of hoses.

3.5 Pressures and safety factors
3.5.1 General
A hose can never function as a safety device for the system. When selecting a hose for a particular
application, irrespective of the hose material, the maximum allowable pressure of the hose should therefore
exceed the operating pressure of the system into which the hose is installed. This also applies to the
assembled hose end connections. The user should always relate the maximum working pressures indicated in
the manufacturer's documentation to the maximum allowable pressure of the desired end couplings and vice
versa.
6 © ISO 2003 — All rights reserved

Maximum working, proof and minimum burst pressures are normally indicated in the manufacturer's
documentation concerned, leaving end connections out of consideration. For example, for a hose with a
maximum working pressure, as quoted by the manufacturer, of 40 bar at −10 °C to +38 °C and assembled
with couplings rated for a lower pressure, the maximum working pressure of the assembly will be reduced.
The assembly should be tested to the required pressures.
3.5.2 Types of pressure
3.5.2.1 Constant pressure
Constant pressure is when the pressure no longer varies once the hose has been pressurized. It only needs
to be checked as to whether the hose is suitable for the operating circumstances.
3.5.2.2 Fluctuating pressure
Fluctuating pressure varies between a minimum and a maximum with a certain regularity. If the variations do
not occur rapidly, it is sufficient to check that the hose is suitable for maximum operating conditions.
3.5.2.3 Pulsating pressure
Pulsating pressure or “cyclic pressure” varies continuously at fixed intervals e.g. with plunger pumps. With
each pulse, the material stress is raised, so that material fatigue may occur more rapidly. In order to ensure a
viable working life, where pulsating pressures are involved a burst pressure/working pressure ratio of at least
4:1 (see ISO 7751) is normal.
3.5.2.4 Intermittent pressures
Peak pressures arising at irregular intervals may be caused e.g. by fast-closing sealing elements (quick shut-
off valves). If a slow-operating pressure gauge is used, it might not indicate the peak pressure so that it is
possible hose damage and leakage to occur within a short period.
If peak pressures are anticipated, they may be measured with the aid of an oscilloscope. In order to achieve a
reasonable working life for the hoses, a burst pressure/working pressure ratio of 5:1 should be adopted.
NOTE It is recommended that, where pulsating or intermittent pressures arise, this is discussed with the
manufacturer or supplier.
3.6 Installation and handling of hoses
3.6.1 General
Reference is made, throughout this report, to the minimum bending radius of hoses. This also means that a
different bending radius applies to each type of hose. Standards for hoses normally include requirements for
minimum bend radius. A 50 mm hose reinforced with a spiral has a smaller minimum bending radius than a
hose with 50 mm bore without spiral. A corrugated hose has a smaller minimum bending radius than a
“smooth” hose whether or not it is fitted with a spiral. See Figures 2 and 3.
Figure 2 — Bending radius
Figure 3 — Bending radius of corrugated hose with spiral
A hose should be installed with caution. The correct and incorrect installation of hoses is indicated in Figures 4
to 18. A hose should be of the right length and no tension should be exerted on the connecting points. If hoses
are incorrectly installed, the bending stress adjacent to the fixed connections will be excessive.
Figure 4 shows an incorrect installation and how a hose kinks adjacent to the couplings. The hose then has a
very short working life. The installed hose shown in Figure 5 will last much longer.
It should be remembered that the weakest point of a hose is generally immediately adjacent to the couplings.
The length of hose required for installation can be calculated by adding 6 to 10 times the internal diameter to
the length of the arc of the bend (see Figure 5).
8 © ISO 2003 — All rights reserved

INCORRECT CORRECT
Figure 4 Figure 5
Hoses should not be installed as illustrated in Figures 6, 7 and 8. The working life will be shortened even
further if the hoses are fitted at points where vibration is heavy. The correct fitting is shown in Figure 9. When
both connecting points are provided with an elbow, the hose will last much longer.

INCORRECT INCORRECT
Figure 6 Figure 7
INCORRECT CORRECT
Figure 8 Figure 9
Incorrect installation may cause compression of the longitudinal axis. This fault may arise both during
installation, as in Figure 10, and during movement, as indicated in Figure 11.

INCORRECT INCORRECT
Figure 10 Figure 11
Torsional movements lead to rapid fracture in hoses and are generally caused by incorrect installation, see
Figure 12. It should be ensured that the hose centrelines run in parallel as in Figure 13, where the directions
of movement lie within the same plane.

INCORRECT CORRECT
Figure 12 Figure 13
10 © ISO 2003 — All rights reserved

Rotation, especially with threaded couplings, may produce torsion. The hose should therefore be held with a
second spanner. Torsion can be avoided as indicated in Figure 14.

CORRECT
Figure 14
Incorrect installation is shown in Figures 15 and 16.

INCORRECT INCORRECT
Figure 15 Figure 16
Deformation and torsion of the hose will be avoided if a support is provided as in Figure 17 or 18.

CORRECT CORRECT
Figure 17 Figure 18
A shaped support can be used to prevent sagging (Figure 16), as shown in Figure 17 or 18. If the support is
provided with a balance weight, the hose will also retain a good bending radius without the hose connections
being overloaded (Figure 18).
It is not always easy, in a pipe system, to install two “permanent” flanges in such a way that the bolt holes line
up precisely. To avoid twisting hoses with flange end connections, hoses should be fitted with one “swivel”
(pivoting) flange. Hoses with diameters exceeding 50 mm may have a coloured stripe over their entire length.
This is called a “longitudinal” stripe. The stripe will show if a hose is twisted during installation. The hose
should then be “disconnected” and refitted. A hose may sometimes have to be used in situations where it is
exposed to horizontal and vertical movement simultaneously during use. The torsion then arising in the hose
may be fatal to it. The correct installation is a so-called “dog-leg”, where two hoses are mounted with a 90°
metal elbow between them (see Figure 19).
12 © ISO 2003 — All rights reserved

Figure 19 — “Dog-leg” installation
In principle, the hose in one leg absorbs the expansion of the other leg and vice versa. The hoses can also
relieve each other, so that partial movements which are not lying in the same plane are still absorbed.
No hoses can be exposed to bending without restriction. They cannot absorb axial forces and may not be
twisted. Sharp bends should be avoided. With frequent bending occurring in a regular cycle, the minimum
bending radius as quoted by the manufacturer should be strictly adhered to, special attention being paid to the
increasing of the minimum bending radius with high operating temperatures and pressures.
During installation, pipelines connected to hoses should be adequately supported so that their weight is never
taken up by the hoses, as this may cause the reinforcing braiding to “distort” so that it no longer supports the
inner hose wall beneath the reinforcement against the internal pressure.
3.6.2 Contact with media
Hoses should not normally come into contact internally or externally with media such as oil, solvents,
corrosive substances, etc. unless the hose has been specially designed for this purpose. In the event of doubt,
the manufacturer should be consulted.
3.6.3 End connections
End connections, unless fitted by the manufacturer during production, should be of a design (including the
incorporated couplings) approved by the manufacturer.
WARNING — Failure to follow the manufacturer's instructions regarding care, maintenance and
storage (see 4.5 and 5.5) of hoses may result in their not functioning in the right way and causing
bodily injury and/or damage to property.
3.7 Inspection and testing
3.7.1 General
The condition of hoses in critical applications should be regularly tested. The more critical the application, the
more frequently they should be tested. Reference may be made to the manufacturer for this purpose. There is
a large number of standards describing hose test methods. They should be used where possible. See the
Bibliography.
Various bodies and firms prescribe periodic inspection for certain hoses, which should then be tested for the
recommended pressure in each case dependent on type, application and frequency of use.
3.7.2 Visual inspection
Hoses and connections should be visually inspected for damage, blisters and non-bonded sections of the
cover of the hose. Rubber hoses should be inspected for soft areas and for any debonding of the
reinforcement.
The weakest part of a rubber hose assembly is usually the section located at a distance of approximately
three times the hose diameter from the inboard end of the hose connection. Blisters or disbonded cover may
be cause for a pressure test to be carried out, or the hose should be replaced. Couplings should be examined
for movement, demonstrated by out-of-line assembly and/or by torn or exposed areas where movement has
occurred. Any evidence of movement of the coupling is a reason for renewing the hose or reassembling the
coupling and re-testing the hose and coupling assembly, where this is permissible.
Small cracks and folds and cloth marking in the cover of the hose that do not penetrate the cover entirely need
not result in replacement.
NOTE The pricking of hoses, e.g. for steam and gas hoses, by the manufacturer is a useful practice. A uniformly
pricked hose should not be regarded with suspicion for that reason. The depth of the pricking should not be more than the
thickness of the cover and subcover.
3.7.3 Periodical testing
Hoses should be periodically tested under pressure in accordance with ISO 1402 at a pressure corresponding
to the product standard or ISO 7751. The pressure test should be carried out with water. Hoses should be
tested in a straight position. The following should be noted in particular.
a) High-pressure air or other compressed gases should not be used as the testing medium because of the
risk of explosion if the hose is not resistant to the pressure test. Air tests under water may be carried out if
acceptable precautions are taken; these tests are usually carried out with low-pressure air to test for leaks
at the hose-coupling connection or porosity throughout the hose walls.
b) The hose should be ventilated through an outlet valve during filling with the testing medium.
c) Steps should be taken to restrict whiplash of the hose in the event of fracturing, but in such a way that
radial expansion and the elongation of the hose under pressure are not restricted.
d) The free end of the hose should be so secured that a loose coupling cannot blow off freely; this can be
done e.g. by a cable connecting the two couplings (with sufficient slack to allow free expansion of the
assembly under test pressure).
e) The personnel carrying out the test should never stand in front of or behind the ends of a hose being
tested.
f) During testing, the hose should be uncoiled to its full length in a dry, clean area without looping or kinking.
The cover and, if possible, the lining should be inspected for blistering, serious damage or cracks; end
connections should also be inspected.
14 © ISO 2003 — All rights reserved

3.7.4 Pressure testing
Following visual inspection, hoses that meet the requirements should be connected to a pressure pump, with
clamps, bolts and nuts being tightened before the pressure test is carried out in accordance with ISO 1402.
A quick-acting valve should be fitted to the end of the hose. Make sure that all connections are tight and fill the
hose with water with the valve open and the end lifted in order to expel the air from the hose.
Close the quick-acting valve when all the air has been expelled. Using the pressure pump, increase pressure
in the hose to that stated in ISO 7751. Examine the hose for leakage, especially at the connections. Look out
for any blistering or swollen parts. Any hose that displays swellings, leakage or tearing should be rejected.
The affected parts may be cut out. The remaining hose length can then again be fitted with couplings and
pressure-tested. If there is no further leakage, it may be assumed that the hose and connections are reliable
and can be used under normal operating conditions.
NOTE It is essential that the precautions mentioned in 3.7.3 are observed when a pressure test is carried out.
3.7.5 Vacuum testing
Suction hoses may be tested under vacuum if applicable. A vacuum test, with both ends of the hose blanked
off with PMMA (“Perspex”) sheet discs (of sufficient thickness) should also be carried out on suction and
discharge hoses to check the integrity of lining-to-reinforcement bond.
3.7.6 Electrical continuity
If electrical continuity is required, this should be tested after the pressure test is completed. The hose should
be tested on a non-conductive support, making use of a suitable resistance meter to determine the resistance
between the couplings (see ISO 8031).
3.7.7 Repairs
Repairs, if allowed, should be carried out in consultation with the supplier after which the hose should be re-
inspected and pressure tested.
3.7.8 Rejection
A hose should be rejected if there is any doubt regarding its operational safety due to:
a) kinking and serious damage to the lining and/or cover wall of the hose, cracks or damaged internal
reinforcement, damage to the textile or wire inlays, or shifting of the latter;
b) wear, tear or corrosion of the outer armouring or metal braiding;
c) swelling or loosening of rubber and reinforcement;
d) corrosion or damage to hose connections;
e) faulty fastening of connections, causing leaks that cannot be fixed;
f) leakage through the hose material;
g) unacceptable deviations from the specified electrical resistance in case of electrically conductive, or semi-
conductive hoses.
Rejected hoses should be destroyed after removal of any couplings or flanges. Couplings that are still found to
be serviceable after a hose has been rejected may be reused in consultation with the hose supplier.
3.7.9 Records
Records should be kept for hoses that are intensively used and/or for critical media. These records should
include an inspection card on which all data for the hose should appear, such as hose identification number,
manufacturer, hose type, standard, date of receipt and commissioning, order number and inspection date. The
length, diameter and hose end connections may also be entered on the card. The inspection card should be
such that all inspection findings can be listed on it. The inspection card number or code should be indicated on
the hose.
3.8 Certificates
3.8.1 New hoses
The supplier/manufacturer should provide a certificate for new hoses that are to be used for critical or
hazardous media. The certificate should at least state the following:
 manufacturer;
 order number (dated);
 make and type of hose as well as the specification and hose serial numbers (optional) covered by the
certificate;
 test pressure;
 any standard according to which the hose has been tested, e.g. national, European or industry standards;
 test date;
 any required electrical resistance of rubber and composite hoses.
3.8.2 Re-inspected and repaired hoses
Hoses that are re-inspected and/or repaired by the supplier/manufacturer should be accompanied by a test
certificate on redelivery with the test results for the hose concerned. If a hose has to conform to certain
electrical conductivity or resistance requirements, the certificate should indicate the value measured.
4 Rubber hoses
4.1 Material
4.1.1 General
Natural or synthetic rubber is homogenized with a number of chemicals mixed in a certain ratio by mixing and
milling equipment, by means of which non-vulcanized rubber compounds are obtained. Apart from the rubber
raw material itself, the added chemicals determine the properties subsequently obtained by the finished
product.
4.1.2 Types of rubber
Although natural rubber is still widely used, synthetic rubber is occupying an ever-greater position. Especially
after World War II, use of this type of rubber became very popular. Synthetic rubber is more suited for certain
purposes than natural rubber. Its resistance to oil, petrol and other hydrocarbons, in particular, means it is
ever-more widely used in the chemical and petro-chemical industries. The main types of rubber are shown in
Table 2 together with their characteristic properties (see also ISO/TR 7620).
16 © ISO 2003 — All rights reserved

Table 2 — Types and properties of rubber
Temp. range Generally Generally
Type of rubber Symbol Special properties
°C resistant to: not resistant to:
Natural rubber NR −50 to +70 Most non-aggressive
Ozone, strong acids, fats,
chemicals, organic High resilience and
oils and most
mechanical strength
acids, alcohols,
Isoprene rubber IR −50 to +70
hydrocarbons
aldehydes, ketones
Styrene butadiene High mechanical
SBR −40 to +80 As for NR/IR As for NR/IR
rubber strength
Resistant to animal
and vegetable fats
Mineral oils, solvents,
Butyl rubber IIR −40 to +130 and oils, alcohols and Gas tightness
aromatic hydrocarbons
ketones, strong and
oxidizing chemicals
Even more highly
Ethylene propylene resistant to ozone
EP(D)M −50 to +130 As for IIR Low water absorption
rubber than IIR & ER,
otherwise as for IIR.
Ozone, chlorinated and
Many hydrocarbons,
nitrohydrocarbons,
Nitrile rubber NBR −25 to +110 fats, oils, hydraulic High oil resistance
ketones, esters and
liquids
aldehydes
Highly oxidizing acids,
Effectively resistant to
esters, ketones,
Chloroprene rubber CR −25 to +100 ozone, oils and fats, Flame-retardant
chlorinated aromatic and
various solvents
nitrohydrocarbons
Chlorinated and
sulfonated CSM −25 to +130 As for CR As for CR Flame-retardant
polythene
Polyether urethane
Concentrated acids,
EU
Effectively resistant to
rubber
ketones and esters,
−20 to +80 ozone, hydrocarbons, Hard-wearing
chlorinated and nitro-
Polyester urethane
fats and oils
AU
hydrocarbons
rubber
Effectively resistant to Concentrated acids, Wide temperature
Silicone rubber MQ −70 to +200
ozone and oxidants many oils and solvents range
Effectively resistant to
Ketones, simple esters
all aliphatic, aromatic Resistance to
Fluoro rubber FMK −25 to +200 and compounds
and chlorinated aromatics
containing a nitro group
hydrocarbons
NOTE The properties are determined not only by the sub-type of the rubber concerned but largely by the composition of the
compounds.
4.1.3 Rubber compounds
A rubber compound may comprise the following:
 rubber: natural or synthetic rubber;
 sulfur: to achieve vulcanization;
 accelerators: for speeding up vulcanization;
 activators: to activate the effect of the accelerators;
 fillers: with or without reinforcing properties;
 softeners: to make the rubber more flexible;
 anti-oxidants: to prevent ageing of the rubber through oxygen;
 colorants: to give the product a particular colour.
4.1.4 Processing of rubber compounds
The homogenized rubber compound (see 4.1.3) consisting of a pliable mass is worked up into the desired
article in the rubber factory. Working up may differ according to the method of manufacture. The product is
vulcanized after moulding.
In vulcanization, which generally takes place at temperatures between 135 °C and 160 °C, a chemical
reaction occurs whereby the rubber mixture changes from a pliable mass into a permanently shaped elastic
material.
4.2 Properties
Hoses made of rubber have to meet a number of requirements. One of these requirements, for example, is
the hardness of the rubber from which the lining of hoses is made. The hardness is often determined by a
hardness meter with a scale gradation of 1 to 100. The hardness is normally expressed in IRHD (International
Rubber Hardness Degrees).
See 3.1 for other required properties.
4.3 Construction
4.3.1 General
A rubber hose consists in principle of a lining around which a reinforcement (single or multi-layered) and a
cover is applied. These parts are described in 4.3.2 to 4.3.7.
4.3.2 Lining
The lining is used to carry media through the hose. The lining protects subsequently located parts of the inner
hose against damage by the medium passing through. Linings are made of a number of types of rubber (see
Table 2). The composition of the lining depends on the application. In some cases, a particular application
requires a lining built up of various materials in order to achieve a combination of different properties.
4.3.3 Lining manufacture
For manufacturing linings, rubbers are mixed in order to achieve the desired composition and properties. The
rubber lining may be either extruded, spirally applied or formed by a so-called “build up method”. In this case,
sheets or strips of rubber are wrapped very uniformly round a mandrel. The mandrel has an external diameter
equal to the desired internal diameter for the hose.
4.3.4 Reinforcing layers
A certain pressure will normally be necessary if a medium is to be carried through a hose. A direct
consequence of this is that the hose needs to be reinforced.
The various pressures determine the type of reinforcement. For low-pressure applications, the reinforcement
may consist of cotton or synthetic textile yarns applied round the lining.
In some cases, metal wire or a combination of textile yarns with metal wire is used.
Wit
...