Top: Rules for the Classification of Steel Ships
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Part C Machinery, Electricity, Automation and Fire Protection
Chapter 4 Fire fighting and prevention
Section 1 General
3.28 Non-sparking fan
3.28.1 A fan is considered as non-sparking if in either normal
or abnormal conditions it is unlikely to produce sparks. For this
purpose, the following criteria are to be met:
- Design criteria
- The air gap between the impeller and the casing
is to be not less than 1/10 of the shaft diameter in way
of the impeller bearing and in any case not less than 2 mm, but
need not exceed 13 mm.
- Protective screens with square mesh of not more than 13
mm are to be fitted to the inlet and outlet of ventilation ducts
to prevent objects entering the fan housing.
- The impeller and the housing in way of the impeller are
to be made of spark-proof materials which are recognised as such
by means of an appropriate test to the satisfaction of the Society.
- Electrostatic charges, both in the rotating body and the
casing, are to be prevented by the use of antistatic materials.
Furthermore, the installation on board of ventilation units is to
be such as to ensure their safe bonding to the hull.
- Tests may not be required for fans having the following
- impellers and/or housings of non-metallic material,
due regard being paid to the elimination of static electricity
- impellers and housings of non-ferrous materials
- impellers of aluminium alloys or magnesium alloys and a ferrous
(including austenitic stainless steel) housing on which a ring of
suitable thickness of non-ferrous material is fitted in way of the
- any combination of ferrous (including austenitic stainless
steel) impellers and housings with not less than 13 mm design tip
- The following impeller and housing combinations are considered
as sparking and therefore are not permitted:
- impellers of an aluminium alloy or a magnesium alloy
and a ferrous housing, regardless of tip clearance
- housings made of an aluminium alloy or a magnesium alloy
and a ferrous impeller, regardless of tip clearance
- any combination of ferrous impeller and housing with less
than 13 mm design tip clearance.
- Complete fans are to be type-tested in accordance with
either the Society's requirements or national or international
standards accepted by the Society.
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