Section
6 Machinery space arrangements
6.1 General
6.2 Structural configuration
6.2.2 For machinery
spaces situated aft, where the longitudinal framing terminates and
is replaced by transverse framing, a suitable scarfing arrangement
of the longitudinal framing is to be arranged. See also
Pt 3, Ch 2, 5.3 Structural continuity.
6.2.3 The maximum
spacing, S
max, of web frames in longitudinally
framed machinery spaces is not to exceed 3,8 m. Additionally for transversely
framed craft, in way of a machinery space situated adjacent to the
aft peak, the spacing of web frames is not to exceed six transverse
frame spaces.
6.3 Structural continuity
6.3.1 Suitable
scarfing arrangements are to be made to ensure continuity of strength
and the avoidance of abrupt discontinuities where structure which
contributes to the main longitudinal strength of the craft is omitted
in way of a machinery space.
6.4 Deck structure
6.4.1 The corners
of machinery space openings are to be of suitable shape and design
to minimise stress concentrations.
6.4.2 In motor craft having a Rule length LR, less than 15 m,
the machinery is to be enclosed by gastight decks to protect accommodation spaces from
gas and vapour fumes from machinery, exhaust and fuel systems.
6.5 Side shell structure
6.5.2 General
requirements for web frames are given in this Section for both longitudinal
and transverse framing systems. Where longitudinal framing is adopted
in the midship region it is to be carried as far forward and aft as
practicable.
6.5.3 A transverse
framing system is to be additionally reinforced by web frames fitted
six frame spaces apart. Where a longitudinal framing system is adopted,
the spacing of the transverses is not to exceed 2,5 m.
6.6 Double and single bottom structure
6.6.1 Flag state requirements for double and single bottom structures are to be
complied with. In the absence of specific Flag state requirements for double and single
bottom structures, arrangements in accordance with SOLAS will be acceptable.
6.6.2 Margin
plates and drainage wells are to be provided as necessary and subject
to special consideration.
6.6.5 In craft
having considerable rise of floor, the depth of the floor plate, or
its height at side, may require to be increased. The transverse extent
of double bottom will be specially considered.
6.6.6 Suitable
arrangements are to be made to provide free passage of water from
all parts of the bilge to the pump suctions.
6.6.7 A centreline
girder is to be fitted in association with transverse frames, transverses
supporting longitudinals or where the breadth of floors at the upper
edge is greater than 1,5 m. Where the breadth of the floors at the
upper edge exceeds 6,0 m a side girder is also to be fitted each side
of the centre girder.
6.6.8 All girders
are to extend as far forward and aft as practicable and care is to
be taken to avoid any abrupt discontinuity.
6.6.9 Centreline
girders fitted in association with flat plate keels are to be formed
of intercostal or continuous plates with a continuous face flat welded
on the upper edge.
6.7 Machinery casings
6.7.2 Where casing
stiffeners carry loads from deck transverses, girders, etc. or where
they are in line with pillars below, they are to be suitably increased. See also
Pt 6, Ch 3, 10 Pillars and pillar bulkheads
Pt 7, Ch 3, 10 Pillars and pillar bulkheads and Pt 8, Ch 3, 10 Pillars and pillar bulkheads,
for craft built in steel, aluminium alloy and composite respectively.
6.7.3 Where casing
sides act as girders supporting decks over, care is to be taken that
access openings do not seriously weaken the structure. Openings are
to be effectively framed and reinforced if found necessary. Particular
care is to be paid to stiffening where the casing supports the funnel
or exhaust uptakes.
6.7.4 Casing
bulkheads are to be made gastight and the access doors are to be of
a gastight self-closing type.
6.8 Integral fuel tanks
6.9 Machinery seatings
6.9.1 Main and
auxiliary engines in motor and auxiliary sailing craft are to be effectively
secured to the hull structure by seatings of adequate scantlings to
resist the gravitational, thrust, torque and vibrating forces which
may be imposed upon them.
6.9.2 The longitudinal
girders forming the engine seatings are to extend as far forward and
aft as practicable and be adequately supported by transverse floors
or brackets.
6.9.3 In determining the scantlings of seats for oil engines, consideration is to
be given to the design characteristics of the engine with regard to out of balance
forces. For machinery room arrangements, see
Pt 5, Ch 1, 4 Machinery room arrangements.
6.9.4 Scantlings for the seats of the drive train should consider the rigidity of its
components and the design characteristics of individual components.
6.9.5 The seats
are to be so designed that they distribute the forces from the engine(s)
as uniformly as possible into the supporting structure. Longitudinal
girders supporting the seatings are to be arranged in single or double
bottoms, and are, in general, to extend over the full length of the
machinery space. The ends of the girders are to be scarfed into the
bottom structure for at least two frame spaces. Adequate transverse
brackets are to be arranged in line with floors. Small brackets may
be required under the top plate in way of holding down bolts.
6.9.6 For gas
turbine installations, seats are to be so designed as to provide effective
support and ensure their proper alignment with the gearing, and, where
applicable, allow for thermal expansion of the casings. In general,
the seats are not to be arranged in way of breaks or recesses in the
double bottom.
6.9.7 Auxiliary
machinery is to be secured on seatings, of adequate scantlings, so
arranged as to distribute the loadings evenly into the supporting
structure.
6.10 Thrust blocks
6.10.1 Main
engines and thrust bearings are to be effectively secured to the hull
structure by seatings of adequate scantlings to resist the various
gravitational, thrust, torque, dynamic and vibratory forces which
may be imposed on them.
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