MEGA Corp. MHT175-CAT777-OPS-1 - Manual (Page 14)

MHT175-CAT777(G)-1
1 Aug 2012
SECTION 2
System Description
2-6
MHT DOOR SYSTEM
The system is comprised of two hinged doors,
activation cylinders, hosing and a proximity
switch (optional). The hydraulic door
cylinders are powered hydraulics from the
tractor hoist valve and controlled by the in-cab
hoist control lever to open and close the doors.
Hydraulics
Doors are opened and closed by hydraulic
cylinders that are mounted on the doors ends
(standard) or center (optional). These
cylinders use hydraulic pressure routed from
the tractor hoist valve to open and close the
doors. The RAISE side of the hoist valve is
used to open the doors while the LOWER side
of the hoist valve is used to close the doors.
Control of the doors is commanded by use of
the in-cab hoist control lever.
Hoist Control Lever
Mounted in the cab and used to open and close
the MHT doors. The lever is labeled for dump
body operations and performs the four
functions of RAISE, HOLD, FLOAT and
LOWER. See the CAT 777(G) operators
manual for more system information.
The MHT uses the in-cab hoist control lever
functions as follows:
RAISE - Open MHT doors.
HOLD - Hold MHT doors in fixed position
for transiting haul roads with or
without a load.
FLOAT – Disable by ECM software for
trailer MHT applications.
LOWER - Close MHT doors.
Door Indicator
A door indicator switch is normally installed
on the MHT lower hopper assembly. The door
switch is intended to contact the inner door
swing arm when the dump doors are in the
closed position and extinguish the dump body
warning light. When the doors are open the
switch will illuminate the dump body warning
light. Under warning light conditions the
ECM will only allow preprogrammed low gear
operations.
.
Hoist Control
Lever
LOWER
FLOAT HOLD
RAISE