Terex TR60 Maintenance Manual page 467

DESCRIPTION
Letters in parentheses refer to Fig. 1.
The Shuttle Valve can be identified as item 6 in
Section 250-0000, BRAKING SYSTEM SCHEMATIC.
The shuttle valve allows the distribution of pressure
from either the treadle valve, to activate the rear
service brakes, or, the retarder control valve, to
utilise the rear service brakes as a retarder.
The shuttle valve consists of a well fitting spool
which is pushed under pressure, depending on flow
direction ('P1' to 'A' or 'P2' to 'A') to one end position,
where it seals against an 'O' ring seal. The 'O' ring is
protected by a metal housing. Flow from 'P1' to 'A', or
'P2' to 'A' can only occur with the valve open.
OPERATION
Refer to Fig. 1. On application of the treadle valve,
hydraulic oil, up to a maximum pressure of 52 bar
(750 lbf/in²), acts on port 'P1'. This pressure pushes
the spool across to close port 'P2'. Oil pressure flows
through port 'A' to the monoblock brake valve
mounted off the left hand frame rail. Refer to
Section 250-0100, MONOBLOCK BRAKE VALVE.
Refer to Fig. 2. On application of the retarder control
valve, hydraulic oil, up to a maximum pressure of
33 bar (480 lbf/in²), acts on port 'P2'. This pressure
pushes the spool across to close port 'P1'. Oil
pressure flows through port 'A' to the monoblock
brake valve mounted off the left hand frame rail.
Refer to Section 250-0100, MONOBLOCK BRAKE
VALVE.
On application of the treadle valve during retarder
operation, treadle valve pressure takes priority at the
shuttle valve when it exceeds retarder applied
pressure. This operation cancels the retarder input
and the rear brakes are applied by the treadle valve.
TESTING
Letters in parentheses refer to Fig. 1.
Remove shuttle valve from the truck (as described
under 'Maintenance') and plug outlet port 'A'. Apply
hydraulic oil pressure of 110 bar (1 600 lbf/in²)
through inlet port 'P1' and visually inspect inlet port
'P2' for leaks. Repeat this test for inlet port 'P2'. If
any leakage of hydraulic oil occurs, replace shuttle
valve.
SM 1229 2-98
BRAKING SYSTEM - Shuttle Valve
FROM 'B2' PORT
TREADLE VALVE
Fig. 1 - Treadle Valve Activated
FROM 'B2' PORT
TREADLE VALVE
Fig. 2 - Retarder Control Valve Activated
MAINTENANCE
The shuttle valve is a non-serviceable item and
should be replaced completely, if damaged, as
follows:
Note: Tighten all fasteners to standard torques listed
in Section 300-0080, STANDARD BOLT AND NUT
TORQUE SPECIFICATIONS.
Note: Tighten all hydraulic lines fitted with ORFS
connections, as described in Section 250-0000,
BRAKING SYSTEM SCHEMATIC. Renew all 'O' rings
where used.
WARNINGS
To prevent personal injury and property
damage, ensure wheel blocks are of sufficient
capacity and properly secured to do the job
safely.
To prevent personal injury, relieve the
pressure in the braking system. The exact
procedure must be followed as described in
Section 250-0000, BRAKING SYSTEM
SCHEMATIC.
Section 250-0140
TO MONOBLOCK
BRAKE VALVE
RETARDER
CONTROL VALVE
TO MONOBLOCK
BRAKE VALVE
RETARDER
CONTROL VALVE
SM - 1350
SM - 1351
1