The user shall, where practicable, cause every power-driven machine consisting of or incorporating two or more rolls rotating in opposite directions, which are less than 75 mm apart, to be guarded for the full length of the in-running side or nip of the rolls where such nip is within the reach of persons, with -
a. a fixed guard; or
b. a trip bar, a cable or an electronic sensing device not more than 300 mm from the nip, which will stop or reverse the rotation of the rolls if the bar or cable is touched or if the danger area is invaded by any foreign object:
Provided that where it is not practicable to install any of the specified devices an inspector may require or permit any other means of protection at the intake of the rolls.