Section
8 Piping
8.1 Fuel oil, hydraulic and high-pressure oil
systems
8.1.2 Engine fuel system components are to be designed to accommodate the maximum
peak pressures experienced in service. Where fuel injection pumps are fitted, particular
attention is to be given to the fuel injection pump supply and spill line piping which
may be subject to high-pressure pulses from the pump. Connections on such piping systems
should be chosen to minimise the risk of pressurised oil fuel leaks. Fatigue analysis
may be considered necessary to establish the suitability of the piping system components
for the pressures and fluctuating stresses that the pipe system may be subject to in
normal service.
8.1.3 On engines used for propulsion, where fuel oil and hydraulic oil pressure
pumps are fitted, and these are essential for engine operation, not less than two fuel
oil and two hydraulic oil pressure pumps are to be provided and arranged such that
failure of one pump does not render the other pump(s) inoperative. Each fuel oil pump
and hydraulic oil pump is to be capable of supplying the quantity of oil for engine
operation at its maximum continuous rating and arranged ready for immediate use.
8.1.4 External high pressure fuel delivery piping between the fuel injection pump
or high pressure fuel pumps and the fuel injectors is to be protected with a jacketed
piping system capable of containing leakage and/or spray of flammable fluid from a high
pressure line failure. The jacketed piping arrangements are to be approved, see
Table 1.1.1 Plans and particulars to be
submitted. The protection of high-pressure fuel pipes
on common rail fuel systems will be specially considered.
8.1.5 The protection required by Vol 2, Pt 2, Ch 1, 8.1 Fuel oil, hydraulic and high-pressure oil systems 8.1.4 is to prevent fuel oil or fuel oil mist from reaching a
source of ignition on the engine or its surroundings. Suitable drainage arrangements are
to be made for draining any fuel oil leakage to one or more collector tank(s) fitted in
a safe position. These tanks are to be separate from any tank used to collect other oils
such as lube oil or hydraulic oil to prevent cross-contamination. An alarm is to be
provided to indicate that leakage is taking place. The collector tank arrangement is to
be approved.
8.1.6 The hydraulic oil pressure piping between the high pressure hydraulic pumps
and hydraulic actuators is to be protected with a jacketed piping system or suitable
enclosure capable of containing hydraulic oil leakage from a high pressure pipe failure.
Where flammable oils are used in high-pressure systems to operate exhaust valves, the
oil pipe lines between the high-pressure oil pump and actuating oil pistons are to be
protected with a jacketed piping system capable of preventing oil spray from a
high-pressure line failure.
8.1.8 Where flammable oils are used in high-pressure actuating systems, a fatigue
analysis is to be carried out in accordance with a suitable standard and all
anticipated pressure, pulsation and vibration loads are to be considered. The analysis
is to demonstrate that the design and arrangements are such that the likelihood of
failure is as low as reasonably practicable. The analysis is to identify all assumptions
made and standards to be applied during manufacture and testing. Any potential weak
points that may develop due to incorrect construction or assembly are also to be
identified.
8.1.9 Accumulators and associated high pressure piping are to be designed,
manufactured and tested in accordance with a standard applicable to the maximum pressure
and temperature rating of the system.
8.1.10 For high pressure oil containing and mechanical power transmission systems,
the quality plan for sourcing, design, installation and testing of components is to
address the following issues (see
Table 1.1.1 Plans and particulars to be
submitted, Note 11):
-
Design and manufacturing standard(s) applied.
-
Materials used for construction of key components and their sources.
-
Details of the quality control system applied during manufacture and
testing.
- Details of type approval, type testing or approved type status assigned to the
machinery or equipment.
-
Details of installation and testing recommendations for the machinery
or equipment.
8.2 Additional requirements for fuel oil, hydraulic and high pressure oil systems for naval vessels
8.2.1 Where multi-engined installations are supplied from the same fuel source,
means of isolating the fuel supply and spill piping to individual engines is to be
provided. These means of isolation are not to affect the operation of the other
engines and are to be operable from a position not rendered inaccessible by a fire
on any of the engines.
8.2.2 Means are to be provided safely to purge the fuel oil system of air.
8.2.3 Short lengths of synthetic rubber hoses that comply with the requirements
of Vol 2, Pt 7, Ch 1, 13 Flexible hoses may be used to accommodate relative
movement between machinery and fixed piping systems.
8.3 Exhaust systems
8.3.1 Where the surface temperature of the exhaust pipes and silencer may exceed
220°C, they are to be water cooled or efficiently lagged to minimise the risk of fire
and to prevent damage by heat. Where lagging covering the exhaust piping system
including flanges is oil-absorbing or may permit penetration of oil, the lagging is to
be encased in sheet metal or equivalent. In locations where the Surveyor is satisfied
that oil impingement could not occur, the lagging need not be encased.
8.3.2 Where the exhausts of two or more engines are led to a common silencer or
exhaust gas-heated boiler or economiser, an isolating device is to be provided in each
exhaust pipe.
8.3.3 For alternatively fired furnaces of boilers using exhaust gases and oil
fuel, the exhaust gas inlet pipe is to be provided with an isolating device and
interlocking arrangements whereby oil fuel can only be supplied to the burners when the
isolating device is closed to the boiler.
8.3.4 In two-stroke main engines fitted with exhaust gas turbochargers which
operate on the impulse system, provision is to be made to prevent broken piston rings
entering the turbine casing and causing damage to blades and nozzle rings.
8.3.5 Where the exhaust is led overboard near the waterline, the exhaust system
shall be so designed as to prevent water from entering the engine exhaust manifold
through wave or wake action, both when the engine is in operation or shutdown. The
system shall also be designed to prevent ingress of water at the angles of inclination
as shown in Vol 2, Pt 1, Ch 3, 4.6 Inclination of ship.
8.3.6 Where the exhaust is cooled by water spray, the exhaust pipes are to be self-draining
overboard. Suitable measures shall be taken to prevent inadvertent closure of drain
valves where this may lead to sprayed water entering the engine. Means shall be provided
to prevent water from flowing back into the engine when the engine is stopped.
8.3.7 Exhaust systems having components sensitive to heat shall be fitted with a high
temperature alarm after water injection. This alarm shall be integrated into the ship’s
alarm system.
8.3.8 Exhaust pipes penetrating the shell below the bulkhead deck shall be provided with a
shipside valve or other approved positive means of closure at the shell to prevent
back-flooding into the hull through a damaged exhaust system.
8.3.9 The exhaust system shall be designed such that the exhaust back-pressure is within the
allowable limits stated by the engine manufacturer under all expected operating
conditions.
8.4 Additional requirements for exhaust systems for naval vessels
8.4.1 The exhausts are to be in accordance with the engine manufacturer's
design and installation requirements. Particular attention is drawn to the
requirements on pressure and flow conditions to be achieved throughout the intake
exhaust systems.
8.4.2 Each engine is to have an independent exhaust system unless arrangements
are made to address risks associated with combined exhausts e.g back pressure,
trapped combustion products and unburned fuel vapours.
8.4.3 The arrangement of the exhaust system is to be such as to prevent
exhaust gases being drawn into the manned spaces, air conditioning systems and air
intakes. They should not discharge into air cushion intakes.
8.4.4 The design of exhaust systems is to prevent deterioration of engine parts
resulting from ingress of sea or rain water via the exhaust ducting when the engine
is not in use. Drainage arrangements are to be provided and are to be led to a tank
suitable for the potentially corrosive nature of any drainage.
8.4.5 Exhaust systems are not to pass through accommodation spaces.
8.4.6 The exhaust system is to accommodate thermal expansion and movement of
the duct due to the combined effects of operating the engines and flexure of the
ship's structure.
8.4.7 The exhaust ducting and silencers are to be designed and installed to
minimise the risk of unburnt fuel collecting inside the duct.
8.4.8 The design of the exhaust ducting and associated equipment is to
minimise the risk of soot collecting at any point other than those specifically
intended for soot removal. Inspection and access openings are to be provided.
8.4.9 Plastic pipes intended for exhaust systems are to be in accordance with a
recognised Code or Standard suitable for the intended service conditions.
8.5 Starting air pipe systems and safety fittings
8.5.1 In
designing the compressed air installation, care is to be taken that
the compressor air inlets will be located in an atmosphere reasonably
free from oil vapour or, alternatively, an air duct from outside the
machinery space is to be led to the compressors.
8.5.2 The
air discharge pipe from the compressors is to be led direct to the
starting air receivers. Provision is to be made for intercepting and
draining oil and water in the air discharge for which purpose a separator
or filter is to be fitted in the discharge pipe between compressors
and receivers.
8.5.3 The
starting air pipe system from receivers to main and auxiliary engines
is to be entirely separate from the compressor discharge pipe system.
Stop valves on the receivers are to permit slow opening to avoid sudden
pressure rises in the piping system. Valve chests and fittings in
the piping system are to be of ductile material.
8.5.4 Drain
valves for removing accumulations of oil and water are to be fitted
on compressors, separators, filters and receivers. In the case of
any low-level pipelines, drain valves are to be fitted to suitably
located drain pots or separators.
8.5.5 The
starting air piping system is to be protected against the effects
of explosions by providing an isolating non-return valve or equivalent
at the starting air supply to each engine.
8.5.6 In
direct reversing engines, bursting discs or flame arresters are to
be fitted at the starting valves on each cylinder; in non-reversing
and auxiliary engines at least one such device is to be fitted at
the supply inlet to the starting air manifold on each engine. The
fitting of bursting discs or flame arresters may be waived in engines
where the cylinder bore does not exceed 230 mm.
8.5.7 Alternative
safety arrangements may be submitted for consideration.
8.6 Requirements for lubricating oil systems
for naval vessels
8.6.1 The
lubrication system for each engine is to be independent from any other
engine. A common lubricating oil storage tank arrangement may be provided.
8.6.2 Each
engine is to be provided with a means of checking the running and
static level of oil in the system/engine.
8.6.3 Means
are to be provided to purge safely lubricating oil systems of air.
8.6.4 All
vent pipes are to be arranged with a continuous upward slope of at
least 10° to prevent the collection of oil in pockets and bends.
8.6.5 Oil
sampling arrangements with the ability to take samples when the engine
is running are to be fitted with valves or cocks of the self-closing
type and located in positions as far removed as possible from any
heated surface or electrical equipment.
8.7 Requirements for air intake systems for
naval vessels
8.7.1 The air intakes are to be in accordance with the engine manufacturer's design and
installation requirements. Particular attention is drawn to the requirements on pressure
and flow conditions to be achieved throughout the intake system.
8.7.2 Engine intakes are to be arranged to provide sufficient air to the engines
whilst minimising the ingestion of harmful particles.
8.7.3 An air
filter is to be fitted at the inlet to each engine. The air filters
are to satisfy the following:
-
Be readily removable
for cleaning.
-
Have an efficiency
of not less than 98 per cent at 100 per cent of rated flow capacity
when tested to an acceptable standard specified by the manufacturer.
-
Be provided with
an indicator, such as a pressure drop indicator, to indicate when
a filter requires cleaning.
-
Be of a design
that does not degrade the performance of the engine.
-
For engines drawing
air from the engine compartment, be as close as possible to the engine
air inlet and in such cases, the debris screen required by Vol 2, Pt 2, Ch 1, 8.7 Requirements for air intake systems for naval vessels 8.7.6.(c) may be omitted.
8.7.5 The
ducting is to be led by the most direct route practicable consistent
with the arrangement of adjacent systems and equipment.
8.7.6 Each
ducted air supply is to have the following:
-
Means to prevent
sea spray, aerosol salt and sand reaching the engine and means to
remove any such substances that enter the intakes or their bypass
arrangements. Suitable drainage arrangements to remove any water from
intakes and intake bypass arrangements (where fitted) to guard against
the risk of icing are also to be provided.
-
Means of ensuring
that loads are not transmitted from the engine to the ducting, such
as a flexible bellows, see
Vol 2, Pt 7, Ch 1, 14 Expansion pieces.
-
A debris screen
that is easily accessible for cleaning located close to the engine.
8.7.7 The
design of induction air systems is to provide a nominal constant air
speed that should be as low as reasonably practicable to minimise
pressure losses. The inlet pressure drop across the system, including
filters and silencers, etc. is not to exceed the engine manufacturer's
recommendations.
8.7.8 Air
induction system intakes are to be designed and installed such that
turbulent flow is not induced therein by ship motions.
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