.-If electric light or instrument or any other electrically-operated equipment is employed on any vehicle including a trailer used in the transportation by road of petroleum other than petroleum Class C-(i)the pressure of the electric circuit shall not exceed 24 volts;(ii)electric wiring shall-(a)be heavily insulated and be adequate for maximum loads to be carried;(b)be provided with suitable over-current protection in the form of fuses or automatic circuit breakers and installed so as to be protected from physical damage and contact with possible product spill either by location or by being encased in metal conduct or other oil resistant protective covering; and(c)have all junction boxes sealed;(iii)the generator, battery, switches, fuses and circuit brackets shall be carried in the cab of the vehicle or in the engine compartment and the battery shall be in an easily accessible position with a heavy-duty switch close by to cut-off the battery;(iv)generators and motors and switches thereof which are not installed within the engine compartment shall be of the approved flame-proof type:Provided that where such generators or motors or switches thereof are installed in an enclosed space, adequate provision shall be made for air circulation to prevent overheating and possible accumulation of inflammable vapours:Provided further that the provisions of this rule except clause (i) and sub-clause (a) of clause (ii) shall not apply for transportation of petroleum Class A otherwise than in bulk exclusively used by helicopters and aeroplanes for aerial crop spraying purposes only.
