Section
10 Safety arrangements
10.1 Relief valves
10.1.1 Scavenge
spaces in open connection with cylinders are to be provided with explosion
relief valves.
10.1.2 Crankcases are to be provided with lightweight spring-loaded valves or
other quick-acting and self-closing devices to relieve the crankcases of pressure in the
event of an internal explosion and to prevent any inrush of air thereafter. The valves
are to be designed and constructed to open quickly and be fully open at a pressure not
greater than 0,02 MPa.
10.1.3 The
valve lids are to be made of ductile material capable of withstanding
the shock of contact with stoppers at the full open position.
10.1.4 Each
valve is to be fitted with a flame arrester that permits flow for
crankcase pressure relief and prevents the passage of flame following
a crankcase explosion. The valves are to be type tested in a configuration
that represents the installation arrangements that will be used on
an engine and in accordance with Pt 5, Ch 2, 14.3 Crankcase explosion relief valves. The valves are to be positioned on engines to minimise
the possibility of danger and damage arising from emission of the
crankcase atmosphere. Where shielding from the emissions is fitted
to a valve, the valve is to be type tested to demonstrate that the
shielding does not adversely affect the operational effectiveness
of the valve.
10.1.5 The
valves are to be provided with a copy of the manufacturer's installation
and maintenance manual for the size and type of valve being supplied
for installation on a particular engine. The manual is to contain
the following information:
- Description of valve with details of function and design limits.
- Copy of type test certification.
- Installation instructions.
- Maintenance and in service instructions to include testing and
renewal of any sealing arrangements.
- Actions required after a crankcase explosion.
10.1.8 The
valves are to be provided with suitable markings that include the
following information:
- Name and address of manufacturer.
- Designation and size.
- Month/Year of manufacture.
- Approved installation orientation.
10.2 Number of relief valves
10.2.1 Internal
combustion engines having a cylinder bore of 200 mm and above or a
crankcase volume of 0,6 m3 and above shall be provided
with crankcase explosion relief valves.
10.2.2 In engines having cylinders exceeding 200 mm but not exceeding 250 mm bore,
at least two relief valves are to be fitted; each valve is to be located at or near the
ends of the crankcase. Where the engine has more than eight crankthrows an additional
valve is to be fitted near the centre of the engine.
10.2.3 In engines having cylinders exceeding 250 mm but not exceeding 300 mm bore,
at least one relief valve is to be fitted in way of each alternate crankthrow with a
minimum of two valves. For engines having 3, 5, 7, 9, etc. crankthrows, the number of
relief valves is not to be less than 2, 3, 4, 5, etc. respectively.
10.2.4 In engines having cylinders exceeding 300 mm bore at least one valve is to
be fitted in way of each main crankthrow.
10.2.5 Additional
relief valves are to be fitted for separate spaces on the crankcase,
such as gear or chaincases for camshaft or similar drives, when the
gross volume of such spaces exceeds 0,6 m3.
10.3 Size of relief valves
10.3.1 The
combined free area of the crankcase relief valves fitted on an engine
is to be not less than 115 cm2/m3 based on the
volume of the crankcase.
10.3.2 The
free area of each relief valve is to be not less than 45 cm2.
10.3.3 The
free area of the relief valve is the minimum flow area at any section
through the valve when the valve is fully open.
10.3.4 In
determining the volume of the crankcase for the purpose of calculating
the combined free area of the crankcase relief valves, the volume
of the stationary parts within the crankcase may be deducted from
the total internal volume of the crankcase.
10.4 Vent pipes
10.4.1 Through
ventilation, and any arrangement which could produce a flow of external
air within the crankcase, is in principle not permitted except for
trunk piston type dual fuel engines where crankcase ventilation is
to be provided. Where crankcase vent or breather pipes are fitted,
they are to be made as small as practicable and/or as long as possible
to minimise the inrush of air after an explosion. Vents or breather
pipes from crankcases of main engines are to be led to a safe position
on deck or other approved position.
10.4.2 If
provision is made for the extraction of gases from within the crankcase,
e.g. for oil mist detection purposes, the vacuum within the crankcase
is not to exceed 25 mm of water.
10.4.3 Lubricating
oil drain pipes from engine sump to drain tank are to be submerged
at their outlet ends. Where two or more engines are installed, vent
pipes, if fitted, and lubrication oil drain pipes are to be independent
to avoid intercommunication between crankcases.
10.5 Warning notice
10.5.1 A
warning notice is to be fitted in a prominent position, preferably
on a crankcase door on each side of the engine, or alternatively at
the engine room control station. This warning notice is to specify
that whenever overheating is suspected in the crankcase, the crankcase
doors or sight holes are not to be opened until a reasonable time
has elapsed after stopping the engine, sufficient to permit adequate
cooling within the crankcase.
10.6 Crankcase access and lighting
10.6.1 Where
access to crankcase spaces is necessary for inspection purposes, suitably
positioned rungs or equivalent arrangements are to be provided as
considered appropriate.
10.6.2 When interior lighting is provided it is to be flameproof in relation to the
interior and details of which are to be submitted for approval. No wiring is to be
fitted inside the crankcase.
10.7 Fire-extinguishing system for scavenge manifolds
10.7.1 Crosshead
type engine scavenge spaces in open connection with cylinders are
to be provided with approved fixed or portable fire-extinguishing
arrangements which are to be independent of the fire-extinguishing
system of the engine room.
10.8 Oil mist detection
10.8.1 Oil mist detection, or engine bearing temperature monitors are to be provided:
- When arrangements are fitted to override the automatic shutdown for excessive
reduction of the lubricating oil supply pressure.
- For engines of 2250 kW and above or having cylinders of more than 300 mm bore.
10.8.3 The
oil mist detection system and arrangements are to be installed in
accordance with the engine designer's and oil mist detection equipment
manufacturer's instructions/recommendations. The following particulars
are to be included in the instructions:
-
A schematic
layout of the engine oil mist detection and alarm system showing locations
of engine crankcase sample points and cabling/piping arrangements
together with pipe dimensions to the detector.
-
Evidence of study
to justify the selected locations of sample points and sample extraction
rate (if applicable) in consideration of the crankcase arrangements
and geometry and the predicted crankcase atmosphere where oil mist
can accumulate.
-
The manufacturer's
maintenance and test manual.
-
Information relating
to type or in-service testing of the engine with engine protection
system test arrangements having approved types of oil mist detection
equipment.
10.8.5 Oil
mist detection and alarm information is to be capable of being read
from a safe location away from the engine.
10.8.6 In
the case of multi engine installations, each engine is to be provided
with individual, dedicated oil mist detection arrangements and alarm(s).
10.8.7 Oil
mist detection and alarm systems are to be capable of being tested
on the test bed and on board when the engine is at a standstill and
when the engine is running at normal operating conditions in accordance
with test procedures that are acceptable to LR.
10.8.10 The
oil mist detection system is to provide an indication that any lenses
fitted in the equipment and used in determination of the oil mist
level have been partially obscured to a degree that will affect the
reliability of the information and alarm indication.
10.8.11 Where
oil mist detection equipment includes the use of programmable electronic
systems, the arrangements are to be in accordance with Pt 6, Ch 1 Control Engineering Systems as applicable.
10.8.13 The
equipment together with detectors is to be tested when installed on
the test bed and on board ship to demonstrate that the detection and
alarm system functions correctly. The testing arrangements are to
be to the satisfaction of the Surveyor.
10.8.14 Where
sequential oil mist detection arrangements are provided, the sampling
frequency and time is to be as short as reasonably practicable.
10.8.15 Where
alternative methods are provided for the prevention of the build-up
of oil mist that may lead to a potentially explosive condition within
the crankcase, detailed information is to be submitted for consideration.
The information is to include:
-
Engine particulars
– type, power, speed, stroke, bore and crankcase volume.
-
Details of arrangements
designed to prevent the build up of potentially explosive conditions
within the crankcase, e.g. bearing temperature monitoring, oil splash
temperature monitoring, crankcase pressure monitoring, and recirculation
arrangements.
-
Evidence to
demonstrate that the arrangements are effective in preventing the
build up of potentially explosive conditions together with details
of in-service experience.
-
Operating instructions
and the maintenance and test instructions.
10.8.16 Where
it is proposed to use the introduction of inert gas into the crankcase
to minimise a potential crankcase explosion, details of the arrangements
are to be submitted for consideration.
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