Autoquip BASCULE BRIDGE - DOUBLE LEAF - Manual (Page 7)

SAFETY FEATURES
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 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.
SAFETY RELEASE BYPASS VALVE (SRBV)
The SRBV is a part of the hydraulic system. Should the system pressure exceed the
predetermined pressure setting, the SRBV will bypass the pump output back to the oil
reservoir. The SRBV is factory set to the proper pressure, which will prevent damage to
the mechanical, hydraulic, and electrical systems due to overloading, obstruction, or
other circumstances.
SAFETY LEGS / SAFETY WINGS
The safety legs are automatic devices which serve two critical safety functions:
1. If the bridge is left open over a long period of time (possibly over the weekend) a
slow downward drift may occur due to the normal bleeding of hydraulic pressure
across the valve seats in the check valve and dump valve. In the extended
position, the safety legs will make contact with the adjacent curb angles, prevent
the bridge from drifting any further, and maintain the bridges vertical position.
2. If the bridge were to experience a sudden and unexpected loss of hydraulic
pressure while being stored in the vertical position, the safety legs would support
the bridge until repairs could be made.
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