Goal
To ensure the safe handling of all cargo and process liquid and vapour, under all
operating conditions, to minimize the risk to the ship, crew and to the
environment, having regard to the nature of the products involved. This
will:
-
.1
ensure the integrity of process pressure vessels, piping systems and
cargo hoses;
-
.2
prevent the uncontrolled transfer of cargo;
-
.3
ensure reliable means to fill and empty the containment systems; and
-
.4
prevent pressure or vacuum excursions of cargo containment systems,
beyond design parameters, during cargo transfer operations.
5.1
General
5.1.1 The requirements of this chapter shall apply to
products and process piping, including vapour piping, gas fuel piping and vent lines
of safety valves or similar piping. Auxiliary piping systems not containing cargo
are exempt from the general requirements of this chapter.
5.1.2 The requirements for type C independent tanks
provided in chapter 4 may also apply to process pressure vessels. If so required,
the term "pressure vessels" as used in chapter 4, covers both type C independent
tanks and process pressure vessels.
5.1.3 Process pressure vessels include surge tanks,
heat exchangers and accumulators that store or treat liquid or vapour cargo.
5.2 System requirements
5.2.1 The cargo handling and cargo control systems
shall be designed taking into account the following:
-
.1 prevention of an abnormal condition
escalating to a release of liquid or vapour cargo;
-
.2 the safe collection and disposal of cargo
fluids released;
-
.3 prevention of the formation of flammable
mixtures;
-
.4 prevention of ignition of flammable liquids
or gases and vapours released; and
-
.5 limiting the exposure of personnel to fire
and other hazards.
5.2.2
Arrangements: general
5.2.2.1 Any piping system that may contain cargo liquid
or vapour shall:
-
.1 be segregated from other piping systems,
except where interconnections are required for cargo-related operations such
as purging, gas-freeing or inerting. The requirements of 9.4.4 shall be
taken into account with regard to preventing back-flow of cargo. In such
cases, precautions shall be taken to ensure that cargo or cargo vapour
cannot enter other piping systems through the interconnections;
-
.2 except as provided in chapter 16, not pass
through any accommodation space, service space or control station or through
a machinery space other than a cargo machinery space;
-
.3 be connected to the cargo containment system
directly from the weather decks except where pipes installed in a vertical
trunkway or equivalent are used to traverse void spaces above a cargo
containment system and except where pipes for drainage, venting or purging
traverse cofferdams;
-
.4 be located in the cargo area above the
weather deck except for bow or stern loading and unloading arrangements in
accordance with 3.8, emergency cargo jettisoning piping systems in
accordance with 5.3.1, turret compartment systems in accordance with 5.3.3
and except in accordance with chapter 16; and
-
.5 be located inboard of the transverse tank
location requirements of 2.4.1, except for athwartship shore connection
piping not subject to internal pressure at sea or emergency cargo
jettisoning piping systems.
5.2.2.2 Suitable means shall be provided to relieve the
pressure and remove liquid cargo from loading and discharging crossover headers;
likewise, any piping between the outermost manifold valves and loading arms or cargo
hoses to the cargo tanks, or other suitable location, prior to disconnection.
5.2.2.3 Piping systems carrying fluids for direct
heating or cooling of cargo shall not be led outside the cargo area unless a
suitable means is provided to prevent or detect the migration of cargo vapour
outside the cargo area (see 13.6.2.6).
5.2.2.4 Relief valves discharging liquid cargo from the
piping system shall discharge into the cargo tanks. Alternatively, they may
discharge to the cargo vent mast, if means are provided to detect and dispose of any
liquid cargo that may flow into the vent system. Where required to prevent
overpressure in downstream piping, relief valves on cargo pumps shall discharge to
the pump suction.
5.3 Arrangements for cargo piping outside the cargo
area
5.3.1
Emergency cargo jettisoning
If fitted, an emergency cargo jettisoning piping system shall comply
with 5.2.2, as appropriate, and may be led aft, external to accommodation spaces,
service spaces or control stations or machinery spaces, but shall not pass through
them. If an emergency cargo jettisoning piping system is permanently installed, a
suitable means of isolating the piping system from the cargo piping shall be
provided within the cargo area.
5.3.2
Bow and stern loading arrangements
5.3.2.1 Subject to the requirements of 3.8, this
section and 5.10.1, cargo piping may be arranged to permit bow or stern loading and
unloading.
5.3.2.2 Arrangements shall be made to allow such piping
to be purged and gas-freed after use. When not in use, the spool pieces shall be
removed and the pipe ends blank-flanged. The vent pipes connected with the purge
shall be located in the cargo area.
5.3.3
Turret compartment transfer systems
For the transfer of liquid or vapour cargo through an internal turret
arrangement located outside the cargo area, the piping serving this purpose shall
comply with 5.2.2, as applicable, 5.10.2 and the following:
-
.1 piping shall be located above the weather
deck, except for the connection to the turret;
-
.2 portable arrangements shall not be
permitted; and
-
.3 arrangements shall be made to allow such
piping to be purged and gas-freed after use. When not in use, the spool
pieces for isolation from the cargo piping shall be removed and the pipe
ends blank-flanged. The vent pipes connected with the purge shall be located
in the cargo area.
5.3.4
Gas fuel piping systems
Gas fuel piping in machinery spaces shall comply with all applicable
sections of this chapter in addition to the requirements of chapter 16.
5.4 Design pressure
5.4.1 The design pressure Po
, used to determine minimum scantlings of piping and piping system components,
shall be not less than the maximum gauge pressure to which the system may be
subjected in service. The minimum design pressure used shall not be less than 1 MPa
gauge, except for open-ended lines or pressure relief valve discharge lines, where
it shall be not less than the lower of 0.5 MPa gauge, or 10 times the relief valve
set pressure.
5.4.2 The greater of the following design conditions
shall be used for piping, piping systems and components, based on the cargoes being
carried:
-
.1 for vapour piping systems or components that
may be separated from their relief valves and which may contain some liquid,
the saturated vapour pressure at a design temperature of 45°C. Higher or
lower values may be used (see 4.13.2.2); or
-
.2 for systems or components that may be
separated from their relief valves and which contain only vapour at all
times, the superheated vapour pressure at 45°C. Higher or lower values may
be used (see 4.13.2.2), assuming an initial condition of saturated vapour in
the system at the system operating pressure and temperature; or
-
.3 the MARVS of the cargo tanks and cargo
processing systems; or
-
.4 the pressure setting of the associated pump
or compressor discharge relief valve; or
-
.5 the maximum total discharge or loading head
of the cargo piping system considering all possible pumping arrangements or
the relief valve setting on a pipeline system.
5.4.3 Those parts of the liquid piping systems that may
be subjected to surge pressures shall be designed to withstand this pressure.
5.4.4 The design pressure of the outer pipe or duct of
gas fuel systems shall not be less than the maximum working pressure of the inner
gas pipe. Alternatively, for gas fuel piping systems with a working pressure greater
than 1 MPa, the design pressure of the outer duct shall not be less than the maximum
built-up pressure arising in the annular space considering the local instantaneous
peak pressure in way of any rupture and the ventilation arrangements.
5.5 Cargo system valve requirements
5.5.1.1 Every cargo tank and piping system shall be
fitted with manually operated valves for isolation purposes as specified in this
section.
5.5.1.2 In addition, remotely operated valves shall
also be fitted, as appropriate, as part of the emergency shutdown (ESD) system the
purpose of which is to stop cargo flow or leakage in the event of an emergency when
cargo liquid or vapour transfer is in progress. The ESD system is intended to return
the cargo system to a safe static condition so that any remedial action can be
taken. Due regard shall be given in the design of the ESD system to avoid the
generation of surge pressures within the cargo transfer pipework. The equipment to
be shut down on ESD activation includes manifold valves during loading or discharge,
any pump or compressor, etc., transferring cargo internally or externally (e.g. to
shore or another ship/barge) and cargo tank valves, if the MARVS exceeds 0.07
MPa.
5.5.2
Cargo tank connections
5.5.2.1 All liquid and vapour connections, except for
safety relief valves and liquid level gauging devices, shall have shutoff valves
located as close to the tank as practicable. These valves shall provide full closure
and shall be capable of local manual operation. They may also be capable of remote
operation.
5.5.2.2 For cargo tanks with a MARVS exceeding 0.07 MPa
gauge, the above connections shall also be equipped with remotely controlled ESD
valves. These valves shall be located as close to the tank as practicable. A single
valve may be substituted for the two separate valves, provided the valve complies
with the requirements of 18.10.2 and provides full closure of the line.
5.5.3
Cargo manifold connections
5.5.3.1 One remotely controlled ESD valve shall be
provided at each cargo transfer connection in use to stop liquid and vapour transfer
to or from the ship. Transfer connections not in use shall be isolated with suitable
blank flanges.
5.5.3.2 If the cargo tank MARVS exceeds 0.07 MPa, an
additional manual valve shall be provided for each transfer connection in use, and
may be inboard or outboard of the ESD valve to suit the ship's design.
5.5.4 Excess flow valves may be used in lieu of ESD
valves, if the diameter of the protected pipe does not exceed 50 mm. Excess flow
valves shall close automatically at the rated closing flow of vapour or liquid as
specified by the manufacturer. The piping including fittings, valves and
appurtenances protected by an excess flow valve shall have a capacity greater than
the rated closing flow of the excess flow valve. Excess flow valves may be designed
with a bypass not exceeding the area of a 1 mm diameter circular opening to allow
equalization of pressure after a shutdown activation.
5.5.5 Cargo tank connections for gauging or measuring
devices need not be equipped with excess flow valves or ESD valves, provided that
the devices are constructed so that the outward flow of tank contents cannot exceed
that passed by a 1.5 mm diameter circular hole.
5.5.6 All pipelines or components which may be isolated
in a liquid full condition shall be protected with relief valves for thermal
expansion and evaporation.
5.5.7 All pipelines or components which may be isolated
automatically due to a fire with a liquid volume of more than 0.05 m3
entrapped shall be provided with PRVs sized for a fire condition.
5.6 Cargo transfer arrangements
5.6.1 Where cargo transfer is by means of cargo pumps
that are not accessible for repair with the tanks in service, at least two separate
means shall be provided to transfer cargo from each cargo tank, and the design shall
be such that failure of one cargo pump or means of transfer will not prevent the
cargo transfer by another pump or pumps, or other cargo transfer means.
5.6.2 The procedure for transfer of cargo by gas
pressurization shall preclude lifting of the relief valves during such transfer. Gas
pressurization may be accepted as a means of transfer of cargo for those tanks where
the design factor of safety is not reduced under the conditions prevailing during
the cargo transfer operation. If the cargo tank relief valves or set pressure are
changed for this purpose, as it is permitted in accordance with 8.2.7 and 8.2.8, the
new set pressure shall not exceed Ph
as is defined in 4.13.2.
5.6.3
Vapour return connections
Connections for vapour return to the shore installations shall be
provided.
5.6.4
Cargo tank vent piping systems
The pressure relief system shall be connected to a vent piping system
designed to minimize the possibility of cargo vapour accumulating on the decks, or
entering accommodation spaces, service spaces, control stations and machinery
spaces, or other spaces where it may create a dangerous condition.
5.6.5
Cargo sampling connections
5.6.5.1 Connections to cargo piping systems for taking
cargo liquid samples shall be clearly marked and shall be designed to minimize the
release of cargo vapours. For vessels permitted to carry toxic products, the
sampling system shall be of a closed loop design to ensure that cargo liquid and
vapour are not vented to atmosphere.
5.6.5.2 Liquid sampling systems shall be provided with
two valves on the sample inlet. One of these valves shall be of the multi-turn type
to avoid accidental opening, and shall be spaced far enough apart to ensure that
they can isolate the line if there is blockage, by ice or hydrates for example.
5.6.5.3 On closed loop systems, the valves on the
return pipe shall also comply with 5.6.5.2.
5.6.5.4 The connection to the sample container shall
comply with recognized standards and be supported so as to be able to support the
weight of a sample container. Threaded connections shall be tack-welded, or
otherwise locked, to prevent them being unscrewed during the normal connection and
disconnection of sample containers. The sample connection shall be fitted with a
closure plug or flange to prevent any leakage when the connection is not in use.
5.6.5.5 Sample connections used only for vapour samples
may be fitted with a single valve in accordance with 5.5, 5.8 and 5.13, and shall
also be fitted with a closure plug or flange.
5.6.5.6 Sampling operations shall be undertaken as
prescribed in 18.9.
5.6.6
Cargo filters
The cargo liquid and vapour systems shall be capable of being fitted with
filters to protect against damage by extraneous objects. Such filters may be
permanent or temporary, and the standards of filtration shall be appropriate to the
risk of debris, etc., entering the cargo system. Means shall be provided to indicate
that filters are becoming blocked, and to isolate, depressurize and clean the
filters safely.
5.7
Installation requirements
5.7.1
Design for expansion and contraction
Provision shall be made to protect the piping, piping system and
components and cargo tanks from excessive stresses due to thermal movement and from
movements of the tank and hull structure. The preferred method outside the cargo
tanks is by means of offsets, bends or loops, but multi-layer bellows may be used if
offsets, bends or loops are not practicable.
5.7.2
Precautions against low temperature
Low temperature piping shall be thermally isolated from the adjacent
hull structure, where necessary, to prevent the temperature of the hull from falling
below the design temperature of the hull material. Where liquid piping is dismantled
regularly, or where liquid leakage may be anticipated, such as at shore connections
and at pump seals, protection for the hull beneath shall be provided.
5.7.3
Water curtain
For cargo temperatures below -110°C, a water distribution system shall be
fitted in way of the hull under the shore connections to provide a low-pressure
water curtain for additional protection of the hull steel and the ship's side
structure. This system is in addition to the requirements of 11.3.1.4, and shall be
operated when cargo transfer is in progress.
5.7.4
Bonding
Where tanks or cargo piping and piping equipment are separated from the
ship's structure by thermal isolation, provision shall be made for electrically
bonding both the piping and the tanks. All gasketed pipe joints and hose connections
shall be electrically bonded. Except where bonding straps are used, it shall be
demonstrated that the electrical resistance of each joint or connection is less than
1MΩ.
5.8 Piping fabrication and joining details
5.8.1
General
The requirements of this section apply to piping inside and outside the
cargo tanks. Relaxation from these requirements may be accepted, in accordance with
recognized standards for piping inside cargo tanks and open-ended piping.
5.8.2
Direct connections
The following direct connection of pipe lengths, without flanges, may be
considered:
-
.1 butt-welded joints with complete penetration
at the root may be used in all applications. For design temperatures colder
than -10°C, butt welds shall be either double welded or equivalent to a
double welded butt joint. This may be accomplished by use of a backing ring,
consumable insert or inert gas backup on the first pass. For design
pressures in excess of 1 MPa and design temperatures of -10°C or colder,
backing rings shall be removed;
-
.2 slip-on welded joints with sleeves and
related welding, having dimensions in accordance with recognized standards,
shall only be used for instrument lines and open-ended lines with an
external diameter of 50 mm or less and design temperatures not colder than
-55°C; and
-
.3 screwed couplings complying with recognized
standards shall only be used for accessory lines and instrumentation lines
with external diameters of 25 mm or less.
5.8.3
Flanged connections
5.8.3.1 Flanges in flanged connections shall be of the
welded neck, slip-on or socket welded type.
5.8.3.2 Flanges shall comply with recognized standards
for their type, manufacture and test. For all piping, except open ended, the
following restrictions apply:
-
.1 for design temperatures colder than -55°C,
only welded-neck flanges shall be used; and
-
.2 for design temperatures colder than -10°C,
slip-on flanges shall not be used in nominal sizes above 100 mm and socket
welded flanges shall not be used in nominal sizes above 50 mm.
5.8.4
Expansion joints
Where bellows and expansion joints are provided in accordance with 5.7.1,
the following requirements apply:
-
.1 if necessary, bellows shall be protected
against icing; and
-
.2 slip joints shall not be used except within
the cargo tanks.
5.8.5
Other connections
Piping connections shall be joined in accordance with 5.8.2 to 5.8.4,
but for other exceptional cases the Administration may consider alternative
arrangements.
5.9
Welding, post-weld heat treatment and non-destructive testing
5.9.1
General
Welding shall be carried out in accordance with 6.5.
5.9.2
Post-weld heat treatment
Post-weld heat treatment shall be required for all butt welds of pipes
made with carbon, carbon-manganese and low alloy steels. The Administration or
recognized organization acting on its behalf may waive the requirements for thermal
stress relieving of pipes with wall thickness less than 10 mm in relation to the
design temperature and pressure of the piping system concerned.
5.9.3
Non-destructive testing
In addition to normal controls before and during the welding, and to the
visual inspection of the finished welds, as necessary for proving that the welding
has been carried out correctly and according to the requirements of this paragraph,
the following tests shall be required:
-
.1 100% radiographic or ultrasonic inspection
of butt-welded joints for piping systems with design temperatures colder
than -10°C, and with inside diameters of more than 75 mm, or wall
thicknesses greater than 10 mm;
-
.2 when such butt-welded joints of piping
sections are made by automatic welding procedures approved by the
Administration or recognized organization acting on its behalf, then a
progressive reduction in the extent of radiographic or ultrasonic inspection
can be agreed, but in no case to less than 10% of each joint. If defects are
revealed, the extent of examination shall be increased to 100% and shall
include inspection of previously accepted welds. This approval can only be
granted if well-documented quality assurance procedures and records are
available to assess the ability of the manufacturer to produce satisfactory
welds consistently; and
-
.3 for other butt-welded joints of pipes not
covered by 5.9.3.1 and 5.9.3.2, spot radiographic or ultrasonic inspection
or other non-destructive tests shall be carried out depending upon service,
position and materials. In general, at least 10% of butt-welded joints of
pipes shall be subjected to radiographic or ultrasonic inspection.
5.10 Installation requirements for cargo piping
outside the cargo area
5.10.1
Bow and stern loading arrangements
The following requirements shall apply to cargo piping and related
piping equipment located outside the cargo area:
-
.1 cargo piping and related piping equipment
outside the cargo area shall have only welded connections. The piping
outside the cargo area shall run on the weather decks and shall be at least
0.8 m inboard, except for athwartships shore connection piping. Such piping
shall be clearly identified and fitted with a shutoff valve at its
connection to the cargo piping system within the cargo area. At this
location, it shall also be capable of being separated by means of a
removable spool piece and blank flanges, when not in use; and
-
.2 the piping shall be full penetration
butt-welded and subjected to full radiographic or ultrasonic inspection,
regardless of pipe diameter and design temperature. Flange connections in
the piping shall only be permitted within the cargo area and at the shore
connection.
5.10.2
Turret compartment transfer systems
The following requirements shall apply to liquid and vapour cargo piping
where it is run outside the cargo area:
-
.1 cargo piping and related piping equipment
outside the cargo area shall have only welded connections; and
-
.2 the piping shall be full penetration
butt-welded, and subjected to full radiographic or ultrasonic inspection,
regardless of pipe diameter and design temperature. Flange connections in
the piping shall only be permitted within the cargo area and at connections
to cargo hoses and the turret connection.
5.10.3
Gas fuel piping
Gas fuel piping, as far as practicable, shall have welded joints. Those
parts of the gas fuel piping that are not enclosed in a ventilated pipe or duct
according to 16.4.3, and are on the weather decks outside the cargo area, shall have
full penetration butt-welded joints and shall be subjected to full radiographic or
ultrasonic inspection.
5.11
Piping system component requirements
5.11.1 Piping scantlings. Piping systems shall be
designed in accordance with recognized standards.
5.11.2.1 The following criteria shall be used for
determining pipe wall thickness.
5.11.2.2 The wall thickness of pipes shall not be less
than:
-
-
where:
-
t0
|
= |
theoretical thickness, determined by the
following formula: |
-
- with:
-
P
|
= |
design pressure (MPa) referred to
in 5.4; |
D
|
= |
outside diameter (mm); |
K
|
= |
allowable stress (N/mm²) referred to
in 5.11.3; |
e
|
= |
efficiency factor equal to 1 for
seamless pipes and for longitudinally or spirally
welded pipes, delivered by approved manufacturers
of welded pipes, that are considered equivalent to
seamless pipes when non-destructive testing on
welds is carried out in accordance with recognized
standards. In other cases, an efficiency factor of
less than 1, in accordance with recognized
standards, may be required, depending on the
manufacturing process; |
-
b
|
= |
allowance for bending (mm). The value of b
shall be chosen so that the calculated stress in the
bend, due to internal pressure only, does not exceed the
allowable stress. Where such justification is not given,
b shall be: |
-
-
with:
-
r
|
= |
mean radius of the bend (mm); |
-
c
|
= |
corrosion allowance (mm). If corrosion or
erosion is expected, the wall thickness of the piping
shall be increased over that required by other design
requirements. This allowance shall be consistent with
the expected life of the piping; and |
a
|
= |
negative manufacturing tolerance for
thickness (%). |
5.11.2.3 The minimum wall thickness shall be in
accordance with recognized standards.
5.11.2.4 Where necessary for mechanical strength to
prevent damage, collapse, excessive sag or buckling of pipes due to superimposed
loads, the wall thickness shall be increased over that required by 5.11.2.2 or, if
this is impracticable or would cause excessive local stresses, these loads may be
reduced, protected against or eliminated by other design methods. Such superimposed
loads may be due to: supporting structures, ship deflections, liquid pressure surge
during transfer operations, the weight of suspended valves, reaction to loading arm
connections, or otherwise.
5.11.3
Allowable stress
5.11.3.1 For pipes, the allowable stress K referred to
in the formula in 5.11.2 is the lower of the following values:
where:
Rm
|
= |
specified minimum tensile strength at room temperature (N/mm²);
and |
Re
|
= |
specified minimum yield stress at room temperature (N/mm²). If
the stress-strain curve does not show a defined yield stress, the 0.2% proof
stress applies. |
The values of A and B shall be shown on the International Certificate of
Fitness for the Carriage of Liquefied Gases in Bulk required in 1.4.4, and have
values of at least A = 2.7 and B = 1.8.
5.11.4
High-pressure gas fuel outer pipes or ducting scantlings
In fuel gas piping systems of design pressure greater than the critical
pressure, the tangential membrane stress of a straight section of pipe or ducting
shall not exceed the tensile strength divided by 1.5 (Rm
/1.5) when subjected to the design pressure specified in 5.4. The pressure
ratings of all other piping components shall reflect the same level of strength as
straight pipes.
5.11.5
Stress analysis
When the design temperature is -110°C or lower, a complete stress
analysis, taking into account all the stresses due to the weight of pipes, including
acceleration loads if significant, internal pressure, thermal contraction and loads
induced by hog and sag of the ship for each branch of the piping system shall be
submitted to the Administration. For temperatures above -110°C, a stress analysis
may be required by the Administration in relation to such matters as the design or
stiffness of the piping system and the choice of materials. In any case,
consideration shall be given to thermal stresses even though calculations are not
submitted. The analysis may be carried out according to a code of practice
acceptable to the Administration.
5.11.6
Flanges, valves and fittings
5.11.6.1 Flanges, valves and other fittings shall
comply with recognized standards, taking into account the material selected and the
design pressure defined in 5.4. For bellows expansion joints used in vapour service,
a lower minimum design pressure may be accepted.
5.11.6.2 For flanges not complying with a recognized
standard, the dimensions of flanges and related bolts shall be to the satisfaction
of the Administration or recognized organization acting on its behalf.
5.11.6.3 All emergency shutdown valves shall be of the
"fail-closed" type (see 5.13.1.1 and 18.10.2).
5.11.6.4 The design and installation of expansion
bellows shall be in accordance with recognized standards and be fitted with means to
prevent damage due to over-extension or compression.
5.11.7
Ship's cargo hoses
5.11.7.1 Liquid and vapour hoses used for cargo
transfer shall be compatible with the cargo and suitable for the cargo
temperature.
5.11.7.2 Hoses subject to tank pressure, or the
discharge pressure of pumps or vapour compressors, shall be designed for a bursting
pressure not less than five times the maximum pressure the hose will be subjected to
during cargo transfer.
5.11.7.3 Each new type of cargo hose, complete with
end-fittings, shall be prototype-tested at a normal ambient temperature, with 200
pressure cycles from zero to at least twice the specified maximum working pressure.
After this cycle pressure test has been carried out, the prototype test shall
demonstrate a bursting pressure of at least 5 times its specified maximum working
pressure at the upper and lower extreme service temperature. Hoses used for
prototype testing shall not be used for cargo service. Thereafter, before being
placed in service, each new length of cargo hose produced shall be hydrostatically
tested at ambient temperature to a pressure not less than 1.5 times its specified
maximum working pressure, but not more than two fifths of its bursting pressure. The
hose shall be stencilled, or otherwise marked, with the date of testing, its
specified maximum working pressure and, if used in services other than ambient
temperature services, its maximum and minimum service temperature, as applicable.
The specified maximum working pressure shall not be less than 1 MPa gauge.
5.12
Materials
5.12.1 The choice and testing of materials used in
piping systems shall comply with the requirements of chapter 6, taking into account
the minimum design temperature. However, some relaxation may be permitted in the
quality of material of open-ended vent piping, provided that the temperature of the
cargo at the pressure relief valve setting is not lower than -55°C, and that no
liquid discharge to the vent piping can occur. Similar relaxations may be permitted
under the same temperature conditions to open-ended piping inside cargo tanks,
excluding discharge piping and all piping inside membrane and semi-membrane
tanks.
5.12.2 Materials having a melting point below 925°C
shall not be used for piping outside the cargo tanks except for short lengths of
pipes attached to the cargo tanks, in which case fire-resisting insulation shall be
provided.
5.12.3
Cargo piping insulation system
5.12.3.1 Cargo piping systems shall be provided with a
thermal insulation system as required to minimize heat leak into the cargo during
transfer operations and to protect personnel from direct contact with cold
surfaces.
5.12.3.2 Where applicable, due to location or
environmental conditions, insulation materials shall have suitable properties of
resistance to fire and flame spread and shall be adequately protected against
penetration of water vapour and mechanical damage.
5.12.4 Where the cargo piping system is of a material
susceptible to stress corrosion cracking in the presence of a salt-laden atmosphere,
adequate measures to avoid this occurring shall be taken by considering material
selection, protection of exposure to salty water and/or readiness for
inspection.
5.13
Testing requirements
5.13.1
Type testing of piping components
5.13.1.1 Valvesfootnote
Each type of valve intended to be used at a working temperature below
-55°C shall be subject to the following type tests:
-
.1 each size and type of valve shall be
subjected to seat tightness testing over the full range of operating
pressures for bi-directional flow and temperatures, at intervals, up to the
rated design pressure of the valve. Allowable leakage rates shall be to the
requirements of the Administration or recognized organization acting on its
behalf. During the testing, satisfactory operation of the valve shall be
verified;
-
.2 the flow or capacity shall be certified to a
recognized standard for each size and type of valve;
-
.3 pressurized components shall be pressure
tested to at least 1.5 times the rated pressure; and
-
.4 for emergency shutdown valves, with
materials having melting temperatures lower than 925°C, the type testing
shall include a fire test to a standard acceptable to the
Administration.
5.13.1.2 Expansion bellows
The following type tests shall be performed on each type of expansion
bellows intended for use on cargo piping outside the cargo tank and where required
by the Administration or recognized organization acting on its behalf, on those
installed within the cargo tanks:
-
.1 elements of the bellows, not pre-compressed,
shall be pressure tested at not less than five times the design pressure
without bursting. The duration of the test shall not be less than 5 min;
-
.2 a pressure test shall be performed on a type
expansion joint, complete with all the accessories such as flanges, stays
and articulations, at the minimum design temperature and twice the design
pressure at the extreme displacement conditions recommended by the
manufacturer, without permanent deformation;
-
.3 a cyclic test (thermal movements) shall be
performed on a complete expansion joint, which shall withstand at least as
many cycles under the conditions of pressure, temperature, axial movement,
rotational movement and transverse movement as it will encounter in actual
service. Testing at ambient temperature is permitted when this testing is at
least as severe as testing at the service temperature; and
-
.4 a cyclic fatigue test (ship deformation)
shall be performed on a complete expansion joint, without internal pressure,
by simulating the bellows movement corresponding to a compensated pipe
length, for at least 2,000,000 cycles at a frequency not higher than 5 Hz.
This test is only required when, due to the piping arrangement, ship
deformation loads are actually experienced.
5.13.2
System testing requirements
5.13.2.1 The requirements of this section shall apply
to piping inside and outside the cargo tanks.
5.13.2.2 After assembly, all cargo and process piping
shall be subjected to a strength test with a suitable fluid. The test pressure shall
be at least 1.5 times the design pressure (1.25 times the design pressure where the
test fluid is compressible) for liquid lines and 1.5 times the maximum system
working pressure (1.25 times the maximum system working pressure where the test
fluid is compressible) for vapour lines. When piping systems or parts of systems are
completely manufactured and equipped with all fittings, the test may be conducted
prior to installation on board the ship. Joints welded on board shall be tested to
at least 1.5 times the design pressure.
5.13.2.3 After assembly on board, each cargo and
process piping system shall be subjected to a leak test using air, or other suitable
medium, to a pressure depending on the leak detection method applied.
5.13.2.4 In double wall gas-fuel piping systems, the
outer pipe or duct shall also be pressure tested to show that it can withstand the
expected maximum pressure at gas pipe rupture.
5.13.2.5 All piping systems, including valves, fittings
and associated equipment for handling cargo or vapours, shall be tested under normal
operating conditions not later than at the first loading operation, in accordance
with recognized standards.
5.13.3
Emergency shutdown valves
The closing characteristics of emergency shutdown valves used in liquid
cargo piping systems shall be tested to demonstrate compliance with 18.10.2.1.3.
This testing may be carried out on board after installation.