Section
6 Ventilators
6.1 Application
6.1.1 This
Section applies to all ship types and provides requirements for ventilators.
Reference should be made to the specified subdivision and stability
standard(s).
6.2 Protection
6.2.1 In all
spaces where mechanical damage is likely, all air and sounding pipes,
scuppers and discharges, including their valves, controls and indicators,
are to be well protected. This protection is to be of steel or other
equivalent material.
6.3 General
6.3.1 Special
care is to be taken in the design and positioning of ventilator openings
and coamings, particularly in the region of the forward end of superstructures
and other points of high stress. The deck plating in way of the coamings
is to be efficiently stiffened.
6.3.2 Ventilators
from tunnels passing through decks are to have scantlings suitable
for withstanding the pressures to which they may be subjected and
are to be made watertight.
6.4 Coamings
6.4.1 The
scantlings and height of ventilator coamings exposed to the weather
are to be not less than required by Table 4.6.1 Ventilator coaming
requirements but the thickness need not exceed that of the adjacent
deck or bulkhead plating. In particularly exposed positions, the height
of coamings and scantlings may be required to be increased.
Table 4.6.1 Ventilator coaming
requirements
| Feature
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Requirements
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| Height (measured above sheathing if fitted)
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(1) z
c = 900 mm for locations defined in Note 2
z
c = 760 mm elsewhere
|
| Thickness
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(2) t
c = 5,5 + 0,01 d
v mm
where 7,5 mm ≤ t
c ≤10,0 mm
|
| Support
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(3) If z
c > 900 mm the coaming is to be specially supported
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| Symbols
|
|
t
c
|
= |
thickness of coaming, in mm |
|
z
c
|
= |
height of coaming, in mm |
|
d
v
|
= |
internal diameter of coaming, in mm |
|
Note
(1) Where the height of the ventilator
exceeds that given in Item (1), the thickness given by (2) may be
gradually reduced, above that height, to a minimum of 6,5 mm. The
ventilator is to be adequately stayed.
Note
(2) For exposed decks immediately above
the design waterline, e.g. quarter decks and well decks.
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6.4.2 The
height of ventilator coamings may be required to be increased on ships
where this is shown to be necessary by the stability and watertight
subdivision calculations required by the specified subdivision and
stability standard(s), see
Vol 1, Pt 1, Ch 2, 1.1 Framework of Classification 1.1.9. The specified standard may require that
the height of all ventilator coamings are above the angle of down
flooding, see
Vol 1, Pt 3, Ch 2, 1.2 Definitions.
6.4.3 For
gooseneck ventilators, the coaming height is to be measured to the
underside of the bend, this being the lowest point through which water
on deck could pass freely to spaces below.
6.4.4 Where
wall vents are fitted with an internal baffle which rises above the
lower edge of the exterior opening, the coaming height is measured
to the top of the baffle.
6.4.5 Ventilator
coaming heights may be reduced on ships assigned a service area notation SA4. Coaming heights are to be as high as practicable, with
a minimum height of 300 mm.
6.5 Closing appliances
6.5.1 All
ventilator openings are to be provided with efficient weathertight
closing appliances of steel or other equivalent material unless the
height of the coaming is greater than 2,5 m above the weather deck
or 5 m on exposed deck immediately above the design waterline, e.g.
quarter decks and well decks.
6.5.2 Where
ventilators are proposed to be led overboard through an enclosed lower
deck space the closing arrangements are to be submitted for approval.
If such ventilators are led overboard more than 4,5 m above the damage
control deck, closing appliances may be omitted, provided that satisfactory
baffles and drainage arrangements are provided, as in the case of
air intakes or exhaust openings for machinery spaces, which may be
arranged in the sides of the ship.
6.5.3 Mushroom
ventilators closed by a head revolving on a centre spindle (screw-down
head) are acceptable, but the diameter is not to exceed 300 mm.
6.5.4 Mushroom
ventilators with a fixed head and closed by a screw-down plate (screw-down
cover) may be accepted up to a diameter of 750 mm within the forward
0,25L
R.
6.5.5 Wall
ventilators (jalousies) may be accepted provided they are capable
of being closed weathertight by hinged steel gasketed covers secured
by bolts or toggles.
6.5.6 A ventilator
head not forming part of the closing arrangements is to be not less
than 6,5 mm thick.
6.6 Machinery spaces
6.6.1 In general,
ventilators necessary to supply the machinery space continuously are
to have coamings of sufficient height to comply with Vol 1, Pt 3, Ch 4, 6.6 Machinery spaces 6.6.1 without having to fit weathertight
closing appliances. Ventilators to emergency generator rooms are to
be so positioned that closing appliances are not required.
6.6.2 Where
due to ship size and arrangement this is not practicable, lesser heights
for machinery space ventilator coamings fitted with weathertight closing
appliances may be permitted if specified in combination with other
suitable arrangements to ensure uninterrupted, adequate supply of
ventilation to these spaces.
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