Section
7 Flexible hoses
7.1 General
7.1.1 A flexible
hose assembly is a short length of metallic or non-metallic hose normally
with prefabricated end fittings ready for installation.
7.1.2 For
the purpose of approval for the applications in Pt 5, Ch 12, 7.2 Applications, details of the materials and
construction of the hoses, and the method of attaching the end fittings
together with evidence of satisfactory prototype testing, are to be
submitted for consideration.
7.1.3 The use of hose clamps and similar types of end attachments are not to be
used for flexible hoses in piping systems for steam, flammable media, starting air
systems or for sea-water systems where failure may result in flooding. In other piping
systems, the use of hose clamps may be accepted where the working pressure is less than
0,5 MPa and provided that there are two clamps at each end connection.
7.1.4 Flexible hoses are to be limited to a length necessary to provide for
relative movement between fixed and flexibly mounted items of machinery/equipment or
systems. Flexible hose assemblies for essential services or containing either flammable
or toxic substances are not to exceed 1,5 m in length.
7.1.5 Flexible
hoses are not to be used to compensate for misalignment between sections
of piping.
7.1.6 Flexible
hose assemblies are not to be installed where they may be subjected
to torsional deformation (twisting) under normal operating conditions.
7.1.7 The
number of flexible hoses in piping systems mentioned in this Section
is to be kept to a minimum and to be limited for the purpose stated
in Pt 5, Ch 12, 7.2 Applications 7.2.1.
7.1.8 Where
flexible hoses are intended for conveying flammable fluids in piping
systems that are in close proximity to hot surfaces, electrical installation
or other sources of ignition, the risk of ignition due to failure
of the hose assembly and subsequent release of fluids is to be mitigated
as far as practicable by the use of screens or other suitable protection.
7.1.9 Flexible
hoses are to be installed in clearly visible and readily accessible
locations.
7.1.10 The
installation of flexible hose assemblies is to be in accordance with
the manufacturer's instructions and use limitations with particular
attention to the following:
-
Orientation.
-
End connection
support (where necessary).
-
Avoidance of
hose contact that could cause rubbing and abrasion.
-
Minimum bend
radii.
7.1.11 Flexible
hoses are to be permanently marked by the manufacturer with the following
details:
-
Hose manufacturer's
name or trademark.
-
Date of manufacture
(month/year).
-
Designation
type reference.
-
Nominal diameter.
-
Pressure rating
-
Temperature
rating.
Where a flexible hose assembly is made up of items from different
manufacturers, the components are to be clearly identified and traceable
to evidence of prototype testing.
7.2 Applications
7.2.1 Short
joining lengths of flexible hoses complying with the requirements
of this Section may be used, where necessary, to accommodate relative
movement between various items of machinery connected to permanent
piping systems. The requirements of this Section may also be applied
to temporarily-connected flexible hoses or hoses of portable equipment.
7.2.2 Rubber
or plastics hoses, with integral cotton or similar braid reinforcement,
may be used in fresh and sea-water cooling systems. In the case of
sea-water systems, where failure of the hoses could give rise to the
danger of flooding, the hoses are to be suitably enclosed, as indicated
in Pt 5, Ch 13, 2.7 Provision for expansion.
7.2.3 Rubber
hoses, with single, double or more closely woven integral wire braid
or other suitable material reinforcement, or convoluted metal pipes
with wire braid protection, may be used in bilge, ballast, compressed
air, fresh water, sea-water, fuel oil, lubricating oil, Class III
steam, hydraulic and thermal oil systems. Flexible hoses of plastics
materials for the same purposes, such as Teflon or Nylon, which are
unable to be reinforced by incorporating closely woven integral wire
braid are to have suitable material reinforcement as far as practicable.
Where rubber or plastics hoses are used for fuel oil supply to burners,
the hoses are to have external wire braid protection in addition to
the integral wire braid. Flexible hoses for use in steam systems are
to be of metallic construction.
7.2.4 Flexible
hoses are not to be used in high pressure fuel oil injection systems.
7.2.5 The
requirements in this section for flexible hose assemblies are not
applicable to hoses intended to be used in fixed fire-extinguishing
systems.
7.3 Design requirements
7.3.1 Flexible
hose assemblies are to be designed and constructed in accordance with
recognised National or International Standards acceptable to LR.
7.3.2 Flexible
hoses are to be complete with approved end fittings in accordance
with manufacturer's specification. End connections which do not have
flanges are to comply with Pt 5, Ch 12, 2.12 Other mechanical couplings as
applicable and each type of hose/fitting combination is to be subject
to prototype testing to the same standard as that required by the
hose with particular reference to pressure and impulse tests.
7.3.3 Flexible
hose assemblies intended for installation in piping systems where
pressure pulses and/or high levels of vibration are expected to occur
in service, are to be designed for the maximum expected impulse peak
pressure and forces due to vibration. The tests required by Pt 5, Ch 12, 7.4 Testing are to take into consideration
the maximum anticipated in-service pressures, vibration frequencies
and forces due to installation.
7.3.4 Flexible hose assemblies constructed of non-metallic materials intended for
installation in piping systems for flammable media, and sea-water systems where failure
may result in flooding, are to be of fire-resistant type. Non-metallic flexible hoses
used for sea water systems and flammable media, except fuel oil, installed on open decks
having little or no fire risk as defined in SOLAS II-2/Reg. 9.2.3.3.2.2(10) are not
required to be of fire-resistant type. Fire resistance is to be demonstrated by testing
to ISO 15540 and ISO 15541.
7.3.5 Flexible
hose assemblies are to be suitable for the intended location and application,
taking into consideration ambient conditions, compatibility with fluids
under working pressure and temperature conditions consistent with
the manufacturer's instructions and any other applicable requirements
in the Rules.
7.4 Testing
7.4.1 Acceptance
of flexible hose assemblies is subject to satisfactory prototype testing.
Prototype test programmes for flexible hose assembles are to be submitted
by the manufacturer and are to be sufficiently detailed to demonstrate
performance in accordance with the specified Standards.
7.4.2 For
a particular hose type complete with end fittings, the tests, as applicable,
are to be carried out on different nominal diameters for pressure,
burst, impulse and fire resistance in accordance with the requirements
of the relevant Standard. The following Standards are to be used as
applicable:
- ISO 6802 – Rubber and plastics hoses and hose assemblies
with wire reinforcements – Hydraulic impulse test with flexing.
- ISO 6803 – Rubber or plastics hoses and hose assemblies
– Hydraulic – pressure impulse test without flexing.
- ISO 15540 – Ships and marine technology – Fire
resistance of hose assemblies – Test methods.
- ISO 15541 – Ships and marine technology – Fire
resistance of hose assemblies – Requirements for test bench.
- ISO 10380 – Pipework – Corrugated metal hoses
and hose assemblies.
Other Standards may be accepted where agreed by LR.
7.4.3 All
flexible hose assemblies are to be satisfactorily prototype burst
tested to an International Standard* to demonstrate they are able
to withstand a pressure of not less than four times the design pressure
without indication of failure or leakage.
Note * The International Standards, e.g. EN or SAE for burst
testing of non-metallic hoses, require the pressure to be increased
until burst without any holding period at 4 x Maximum Working Pressure.
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