Operation and maintenance manual

Section 220-0140
SM 1395 Rev 1 2-00
1
STEERING SYSTEM - Emergency Valve
SM - 542
DESCRIPTION
The Emergency Valve can be identified as item 4 in
Section 220-0000, STEERING SYSTEM SCHEMATIC.
Located on the inside of the front left hand side frame
rail, the emergency valve forms part of the emergency
steering system. It is connected to the main output line
of the wheel driven emergency steering pump on the
transmission.
OPERATION
Normal Steering
Numbers and letters in parentheses refer to Fig. 1.
Refer to Fig. 2 for hydraulic schematic of emergency
valve during normal steering operation.
During normal operation, pilot pressure from the main
hydraulic pump acts on spool (3), pushing the spool to
the right. The emergency steering pump draws oil from
the hydraulic tank and pumps it to port 'B' of the
emergency valve. The oil is directed through the
emergency valve, exits at port 'C' and returns to the
hydraulic tank.
SM - 543
Fig. 2 - Emergency Valve - Normal Steering Operation
4 - Emergency Valve
6 - Check Valve
1 - Hydraulic Tank
3 - Emergency Pump
FLOW
AMPLIFIER
INLET
STEERING
PUMP
Fig. 1 - Sectional View of Emergency Valve
1 - Retainer
2 - Cage
3 - Spool
4 - Spring Ring
5- Spring
6- Spring
7 - 'O' Ring
8 - 'O' Ring
9 - 'O' Ring
10 - 'O' Ring
11 - 'O' Ring
12 - Backup Washer
13 - Backup Washer
14 - Backup Washer
15 - Backup Washer
16 - Sealing Washer
17 - 'O' Ring