Section 7.322. Drive

(a) Motive power arrangement—all installations. Each escalator shall preferably be driven by an independent electric motor but under no circumstances shall more than two escalators be driven by one motor. The latter arrangement is permissible only when the two are placed so closely together as to be practically one unit.

(b) Chains. The strength of chain drives shall conform to the following:

(1) New installations. Chains used for driving escalator treads shall have a factor of safety of not less than ten when operating with the full capacity at maximum speed, except when the chains are composed of cast steel links, which shall be thoroughly annealed, in which case the factor of safety shall be not less than 20.

(2) Existing installations. Chains used for driving escalator treads shall be of sufficient strength to carry the load without breakage or misplacement. When such chains are in need of renewal, the new chains shall possess a safety factor of not less than ten when the escalator is operating with full capacity at maximum speed.