Non-sparking fans

D.6 Non-sparking fans
D.6.1 Protection screens of not more than 13 mm square mesh are to be fitted in the inlet and outlet
ventilation openings on the open deck to prevent the entrance of objects into the fan housing.
D.6.2 Overheating of the mechanical components of fans and the creation of sparks is to be avoided
by appropriate design and by the choice of suitable materials. The safety clearance between the fan
housing and the impeller shall not be less than 1/10 of the inner impeller bearing diameter, limited to a
minimum of 2 mm and is to be such as to preclude any contact between the housing and the rotor. The
maximum clearance need not be more than 13 mm. The above requirement also applies to portable fans.
D.6.3 Following materials or combinations of materials for impeller/housing may be used:
 non-metallic materials (plastic material having sufficient electric conductivity) with each other or with
steel (incl. galvanized, stainless). The electrical resistance of non-metallic materials must not exceed
106 Ohm unless special measures are taken to prevent electrostatic charges at the surface of the
material.
 non-ferrous materials having good heat conductivity (bronze, brass, copper, not aluminium) with
each other or with steel (incl. galvanized, stainless)
 steel (incl. galvanized, stainless) with each other if a ring of adequate size made of above nonmetallic/non-ferrous
material is fitted in way of the impeller, or if a safety clearance of 13 mm is provided

 aluminium or magnesium alloys with each other or with steel (incl. galvanized, stainless) only, if a
non-ferrous ring having a good heat conductivity, i.e. copper, brass, of adequate size is fitted in way
of the impeller