Manitowoc 777 Service And Maintenance Manual

Reference Only
Manitowoc Published 10-01-2012, Control # 045-08 1-23
777 SERVICE MANUAL INTRODUCTION
1
Limit Switch
See Figure 1-14 for following procedures.
When Kl is energized and contact Kl is closed, voltage is
available to operating limit switches, seat switch, and limit
bypass switch.
The seat switch is located under the operator’s seat. This
switch is closed and all control handle functions become
operable when pressure is exerted downward on the seat by
the operator’s body weight. When the seat switch is opened,
all control handles are inoperable and at the time of
attempted handle actuation, the display will display an
operating limit fault message: FUNCTION IS PARKED.
During normal operation, all limit switches are closed,
completing circuits to the PC. The PC will complete circuits to
the pump EDCs and drum park brake solenoid valves to
allow the pumps to be operated and the park brakes to be
released.
If a limit switch is opened, the PC will open the appropriate
circuit to the pump EDC and the brake solenoid. The pump
then strokes to off and the solenoid valve closes, causing the
brake to apply. Any function can be operated in the opposite
direction to correct the problem.
The limits are actuated and the PC responds as follows:
• BOOM UP LIMIT automatically stops the boom when it
is raised to a preset maximum angle (82° inline top, 83°
Offset top, 88° Luffing Jib).
• BOOM DOWN LIMIT automatically stops the boom
when it is lowered to a preset minimum angle (usually
0°).
• BLOCK-UP LIMIT automatically stops the boom or hoist
from lowering and the load drums from hoisting if the
load contacts a block-up limit switch.
• LUFFING JIB UP LIMIT automatically stops the luffing
jib when the boom-to-luffing angle is 168°.
• LUFFING JIB DOWN LIMIT automatically stops the
luffing jib when the boom-to-luffing jib angle is 60°.
• MAXIMUM BAIL LIMIT automatically stops the
corresponding load drum from hoisting when there is a
preset maximum number of wire rope layers on a drum.
• MINIMUM BAIL LIMIT automatically stops the
corresponding load drum when there are three wraps of
wire rope remaining on the drum.
• SEAT SWITCH prevents the crane from being operated
by rendering all control handles inoperable, maintaining
application of all park brakes, and turning off free fall and
travel detent systems.
FIGURE 1-14

Manitowoc 777 Specifications

General

Brand	Manitowoc
Model	777
Category	Construction Equipment
Language	English