Autoquip FREIGHTLIFT FLT - Manual (Page 12)

12
SAFETY FEATURES
There are several active safety features and devices to help protect personnel, property,
and the equipment.
ZERO DRIFT FEATURE
A zero drift feature has been incorporated into the FREIGHTLITE lift. The zero drift
uses a limit switch mounted at the upper level and the pressure switch circuit. The limit
switch is tripped closed when the carriage is at the upper level. The electrical circuit is
transferred to the pressure switch, if the pressure switch closes due to a pressure drop
or leak. The motor will start momentarily to build pressure until the pressure switch
shuts the motor off. This keeps the platform from drifting downward from the upper
level. When the operator closes all gates and energizes the down pushbutton, the zero
drift circuit is disabled and the carriage will lower.
HYDRAULIC VELOCITY FUSES
Each hydraulic cylinder has a hydraulic velocity fuse (HVF) installed in the cylinder port.
These HVFs are installed in the predetermined hydraulic oil flow velocity as the oil
returns to the reservoir. They do not affect incoming oil. Should a catastrophic rupture
or breach occur in the hydraulic system and oil flows through the breach that exceeds
the HVF rating, the HVF will trigger and lock up. This lock up will occur with one to two
inches of downward movement of the platform carriage.
NOTE: Air in the system will also cause a lock up. Air acts like a spring when
compressed. To remove air from the system, see “Air Bleeding Procedures” in the
General Maintenance section.
NOTE: Small fitting leaks will not trigger the HVFs. In an air-free system, the breach
must be large enough to cause an uncontrolled or destructive lowering speed. Should a
triggering and loc up occur, it can only be released by applying upward hydraulic flow in
a functional system.