7.3.5 Drive Machine
Check the motor to determine that is clean, properly lubricated, and in good operating
condition. Visually check the driving machine fastenings and bearing caps and determine that
they are tight (See Figure 7-10). Visually check the condition of the brake, if possible. Test the
brake application to determine that it applies upon loss of power or actuation of the safety
devices. Also note any excessive backlash in the driving gears. If a chain is used to connect the
driving machine to a sprocket on the main drive shaft, note whether there is adequate, but not
excessive slack in the driving chain. Note the adjustment of the broken-chain device and
whether chain or gears are lubricated. See Figure 7-11. If the drive chain parts or breaks, the
device will cause the application of the brake on the main drive shaft and stop the drive machine.
operate the broken-chain device by hand to verify operation. Inspect V-belts for damage, wear,
tension, and reasonable quality of tension among members of a set. When V-belts are replaced in
multiple drives, a matched set of belts should be used.
7.3.6 Speed Governor
The speed governor, if required, should be checked by tripping the mechanism manually. See
Figure 7-12. Speed governors are not required where an escalator is driven by an AC squirrel
cage induction motor and the motor is directly connected to the driving machine.
7.3.7 Step Chain
Note any excessive slack in the step chains and whether they are lubricated. Lack of adequate
chain lubrication may be indicated by the presence of a red rusty deposit on the side plates of the
chain links. A broken step-chain device shall be provided that will cause the interruption of
power to the driving machine if a step chain breaks, and where no automatic chain tension device
is provided (if excessive sag occurs in either step chain). See Figures 7-13 and 7-14 for a typical
step chain assembly. The broken step-chain device should be operated by hand to determine that
it will apply the brake and stop the escalator. See Figure 7-15.
7.3.8 Tandom Operation
For escalators installed under the 1981 and later editions of the Code, if a common landing is
shared by two or more escalators, where one unit is carrying away passengers,supplied by
another, determine that the unit feeding the landing shuts down when the unit removing the
passengers stops. Determine that the feeding unit cannot be started if the other unit remains
shut off. Also determine that both units are electrically interlocked where they can only run in
the same direction.