(IV-7-3) General Safety

Rules IV Industrial Services
Part 7 Offshore Substations
Chapter 3 General Safety
Section 7
B.2 Ducts
Passive Fire Protection
B.2.1 Where ventilation ducts with a cross-sectional area exceeding 0.02 m 2 pass through class "A"
bulkheads or decks, the opening shall be lined with a steel sheet sleeve unless the ducts passing through
the bulkheads or decks are of steel in the vicinity of penetrations through the deck or bulkhead, the ducts
and sleeves at such places shall comply with the following:
B.2.2 The ducts or sleeves shall have a thickness of at least 3 mm and a length of at least 900 mm.
When passing through bulkheads, this length shall be divided preferably into 450 mm on each side of the
bulkhead.
These ducts, or sleeves lining such ducts, shall be provided with fire insulation. The insulation shall have
at least the same fire integrity as the bulkhead or deck through which the passes. Equivalent penetration
protection shall be provided to the satisfaction of GL.
B.2.3 Ducts with a cross-sectional area exceeding 0.075 m 2 , except those serving hazardous areas,
shall be fitted with fire dampers in addition to meeting the requirements of B.2.2. The fire damper shall
operate automatically but shall also be capable of being closed from both sides of the bulkhead or deck.
The damper shall be provided with an indicator which shows whether the damper is open or closed. Fire
dampers are not required, however, where ducts pass through spaces without serving these spaces,
provided those ducts have the same fire integrity as the divisions which they pierce. GL may, given special
considerations, permit operation from one side of a division only.
B.2.4 A full cross-sectional area of a duct is to be considered for the above requirements. Splitting of
ducts before the penetration and merging afterwards does not relax the requirements.
B.3 Ventilation of machinery spaces, galleys and hazardous areas
B.3.1 Ducts provided for the ventilation of machinery spaces of category "A", galleys and hazardous
areas shall not pass through accommodation spaces, service spaces or control stations. However, GL
may permit a relaxation from this requirement, except for the ducts serving hazardous areas provided
that:
B.3.2 Ducts are constructed of steel having a thickness of at least 3 mm for ducts of 300 mm in
width or less and of at least 5 mm for ducts of 760 mm in width and over; in the case of ducts the width or
diameter of which is between 300 mm and 760 mm, the thickness shall be obtained by interpolation.
B.3.3
Ducts are fitted with automatic fire dampers close to the boundaries penetrated, and
B.3.4 Ducts are insulated in "A-60" standard from the machinery spaces or galleys to a point at least
5 m beyond each fire damper.
Or alternatively:
B.3.5
Ducts are constructed of steel in accordance with B.3.2.
B.3.6 Ducts are insulated to "A-60" standard throughout the accommodation spaces, service spaces
or control stations.
B.4 Ventilation of accommodation spaces, service spaces or control stations
B.4.1 Ducts provided for the ventilation of accommodation spaces, service spaces or control stations
shall not pass through machinery spaces of category A, galleys or hazardous areas. However, GL may
permit a relaxation from this requirement, except for the ducts passing through hazardous areas, provided
that:
B.4.2 The ducts where they pass through a machinery space of category A or a galley are constructed
of steel in accordance with B.3.2.
B.4.3
Automatic fire dampers are fitted close to the boundaries penetrated.
Edition 2013 Germanischer Lloyd Page 7–7