Section
3 System arrangements
3.1 Water storage facilities
3.1.1 Sufficient
potable water storage is to be provided to cater for the needs of
the full ship’s complement and embarked personnel recognising
the operating role of the ship that is to be declared in the System
Design Description required by Vol 2, Pt 11, Ch 1, 1.3 Documentation required for design review 1.3.2.
For example, a ship may be expected to spend some time in littoral
waters where production of fresh water using installed plant may not
be possible due to plant limitations or statutory regulations. The
combination of storage, water production rate and usage is to be carefully
considered in the vessel design, taking into account both average
and peak loadings, the latter of which may be typically three times
the normal usage rate.
3.1.2 At least two storage tanks are to be fitted, each with separate means of
supplying the fresh water distribution main. In NS1 and NS2 type ships these tanks are
not to share a common boundary or be directly cross-connected and at least one of the
tanks is to be sited other than in the double bottom space. The tanks are to be sited
and be of such dimensions that they are readily accessible to facilitate inspection,
cleaning and coating.
3.1.3 The internal structure of fresh water tanks is to be designed to ensure
efficient drainage to the suction point. Access arrangements to storage tanks are to be
arranged and sited clear of sources of possible contamination see also
Vol 1, Pt 3, Ch 2, 4.9 Separation and protection of tanks.
3.1.4 Pipes
other than piping containing fresh water of the same quality as the
tank contents are not to pass through or be located within a fresh
water tank. Pipes carrying fresh water are not to pass through tanks
other than fresh water tanks.
3.1.6 Water
storage tanks are to be provided with means of indicating the water
level. The means of routine level inspection is to be by means other
than by the use of sounding rods.
3.1.7 Air, filling and sounding arrangements for fresh water storage tanks are to
be located and arranged to prevent an ingress of a contaminant. The arrangements for
filling are to include a deck connection to facilitate external loading.
3.1.8 Where
specified, separate storage tank(s) in addition to the two storage
tanks required by Vol 2, Pt 11, Ch 1, 3.1 Water storage facilities 3.1.2 is/are
to be provided. The tank(s) is/are to be provided with means for treatment
of water in the tank for decontamination or other purposes that may
be specified by the Owner.
3.2 Made water production facilities
3.2.1 Made water production facilities fitted are to be capable of producing
water to World Health Organization Guidelines for Drinking Water Quality, Volume 1
Recommendations Second Edition 1994 as a minimum requirement. A more stringent
quality of water production may be necessary in the case of water for use in, for
example, boiler feed systems, battery top-up, or gas turbine washing. In these cases, an
alternative means of water production is to be provided or a further stage of
desalination included in the production arrangements. Where the specified standards for
made water are other than the World Health Organization Standards, these are to be
provided to LR.
3.2.2 The
total capacity of the fresh water generation plant will depend upon
a number of parameters including complement, ship operating profile
and other equipment supplied, but typically will be of the order of
135 litres/man/day plus 450 litres/aircraft/day. The capacity of the
plant and tank storage is to be specified by the Owner and declared
in the System Design Description required by Vol 2, Pt 11, Ch 1, 1.3 Documentation required for design review 1.3.2.
3.2.3 Two
or more plants for making water are to be provided, of sufficient
combined capacity to produce sufficient water under defined levels
of requirements stated in the System Design Description required by Vol 2, Pt 11, Ch 1, 1.3 Documentation required for design review 1.3.2. Provision of single plant
will be considered in conjunction with the operational requirements
of the ship and any assigned service restriction.
3.2.4 The
design of plants for making water is to be such that permits cleaning,
maintenance and repair of any plant whilst the other is in service.
3.2.5 Adequate
cleaning arrangements are to be fitted to water generating plants.
A suitable safe area is to be designated for system cleaning agents.
3.2.6 In
the case of distilling type plants, adequate safeguards are to be
incorporated to prevent excess steam pressure. Steam piping arrangements
are to comply with Vol 2, Pt 7, Ch 3, 5 Steam piping systems.
3.2.7 Where
there are low-pressure evaporators using diesel engine jacket water
as the heating medium, any corrosion inhibitors in the jacket water
are specifically approved for that application.
3.2.8 Means
are to be provided to automatically enable produced water that falls
below specification to be prevented from being discharged into the
supply for distribution into the fresh and made water storage and
user systems. The arrangements are to minimise the risk of contamination
of made water storage facilities if the made water quality from the
plant falls below specification.
3.3 Piping system design
3.3.1 Piping system arrangements are to be such that the supply of made and fresh
water can be made to Mobility and/or Ship Type systems such as chilled water, machinery
fresh water cooling and boiler feed water in the event of a single failure or damage of
a system or item of equipment. As far as possible, permanent connections to these
systems are to be avoided to prevent contamination of the fresh water by additives such
as corrosion inhibitors that may be present in the systems. Where it is essential to fit
permanent connections, means are to be provided to isolate the systems from the fresh
water supplies to ensure that cross contamination cannot take place when the systems are
operating normally.
3.3.3 Where
a piping system has failed or been damaged, any resulting hazards
are to be capable of being minimised.
3.3.4 All
equipment fitted in piping systems is to be readily accessible to
facilitate maintenance and survey. For this purpose, valves or cocks
are to be interposed between items of equipment and the inlet and
outlet pipes in order that any item of equipment may be shut off for
opening up and overhauling.
3.3.5 Any
filter elements fitted in equipment or piping systems are to be capable
of being cleaned and/or changed.
3.3.6 Pressure
relief devices are to be mounted in such a way that it is not possible
to isolate them from the part of the system which they are protecting
except that, where duplicated, a changeover valve may be fitted that
will allow either device to be isolated for maintenance purposes without
it being possible to shut off the other device at the same time.
3.3.8 Not less than two sea inlets are to be provided for pumps supplying
seawater to the fresh water generating plants. The sea inlets are to be independent from
each other and other ship’s services and are to be located forward and clear of any
bilge or sanitary discharges.
3.3.10 Provision
is to be made for all seawater to pass through suitable filters before
being introduced to the made water plant. The filters are to be in
accordance with the equipment manufacturer's recommendations.
3.3.12 The
system is to be capable of being cleaned with arrangements for safely
flushing out any cleaning chemical agents after use and for storing
or disposing of them safely.
3.4 Piping system distribution
3.4.1 Two
or more water pumps are to be provided of sufficient capacity to supply
the water distribution system with any one pump out of action.
3.4.2 The
water distribution system is to be capable of providing a steady flow
of water at any point in the system in accordance with the System
Design Description required by Vol 2, Pt 11, Ch 1, 1.3 Documentation required for design review 1.3.2.
Where a pneumatically pressurised tank arrangement is used, the tank
is to be provided with water level indication and a means of indicating
the pressure. The compressed air connection to the pressurised tank
is to incorporate a non-return valve arrangement at the tank to prevent
the possibility of water entering the compressed air system and it
is recommended that the connection be made via a portable hose connection.
3.4.3 Each
user or group of users of fresh water are to be provided with means
of isolation such that the distribution system can continue to function
when a user or group of users has been isolated.
3.4.4 Air
vent and drain points are to be provided throughout the system at
all high and low points.
3.4.5 Provision
is to be made for filling the water storage system(s) from the made
water production facilities. Shore connection located above the waterline
and an associated dry main are to be provided to permit the filling
of the storage system.
3.4.6 Provision
is to be made to connect an alternative source of water supply to
defined services in emergency/ action damage conditions. For example,
where the fresh water main is unavailable, stand-by arrangements are
to be provided for suitable water supplies to medical spaces, galleys,
bridge window sprays, cleansing stations (CBRN Protection fitted vessels)
and weapon cooling. The supply arrangements to defined services in
emergency/action damage conditions are to be included in the System
Design Description required by Vol 2, Pt 11, Ch 1, 1.3 Documentation required for design review 1.3.2 and
agreed by the Owner.
3.4.7 There
are to be no permanent connections between fresh water and sea water
systems. Where emergency connections have been designed for the supply
of fresh water to fresh and seawater cooled equipment, the fresh water
is to be supplied by means of a portable hose with screw down non-return
valve isolation arrangements at the connection to the equipment.
3.4.8 The
temperature of domestic hot water systems is to be maintained above
63°C except in cases of peak demand when a fall to no less than
60° is acceptable. The distribution system is to be provided with
a means of continuous circulation to resist bacteriological contamination
of the system.
3.4.9 Calorifiers
are to be provided with drainage arrangements and adequate access
to enable cleaning.
3.4.10 Provision
is to be made for all water supplies intended for domestic services
and food preparation to be sterilised by chlorination that maintains
residual free chlorine content of 0,2 ppm or by an equivalent sterilisation
method. Means are also to be provided to chlorinate all fresh water
taken from shore, water barge or supply ship on loading to a sufficient
concentration to ensure a residual free chlorine content of 0,2 ppm.
3.4.11 The
water supply arrangements intended for crew and embarked personnel
for drinking, washing or food preparation is to be independent of
other services wherever possible. Where there are no alternative supply
arrangements to other services requiring fresh water (e.g. machinery
cooling water, purifiers or a fresh water WC flushing system), a clear
air break is to be provided in the fresh water supply pipe to such
a system or tank. If it is impracticable to provide a clear air break,
the supply pipe to each system is to be provided with an efficient
non-return valve and a vacuum breaker or back-flow preventer.
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