Operation and maintenance manual

Section 250-0070
SM 2165 Rev 1 11-03
7
Braking System - Treadle Valve
8. Install new 'O' ring on plug (12) and install into the
counter bore on the bottom of lower valve body (11).
Tighten plug (12) to a torque of 17 - 20 Nm
(150 - 180 lbf in).
9. Lightly lubricate 'O' ring (15) and install into the
counter bore in the top end of lower valve body (11).
10. Assemble lower valve body (11) to upper valve
body (9) assembly, with correct port orientation as
shown in Fig. 1, and secure with capscrews (10).
Tighten capscrews (10) evenly to a torque of
16 - 17 Nm (140 - 150 lbf in).
11. Coat threads of adjusting screw (4) with a thin film
of Loctite Primer T 747. Allow primer to cure (minimum
of one minute), then screw adjusting screw (4) into
actuator piston (7) all the way down until they bottom
on the threads.
Note: It is extremely important to bottom-out
adjustment screw (4) to prevent over pressurization
during initial adjustment procedure. Excessive
regulated output pressure could cause premature
failure of regulator springs.
TESTING AND ADJUSTMENTS
Numbers in parentheses refer to Fig. 1.
Note: A hydraulic test fixture with capabilities similar to
the one shown in Fig. 7 is required.
1. Position the valve in the test fixture to allow plunger
to be activated by hand using a lever. See Fig. 8.
2. Attach pilot input supply pressure to the 'Px' port of
valve body.
3. Attach main supply input pressure to 'P1' and 'P2'
ports of valve body.
4. Attach tank return lines to 'T1' and 'T2' ports of valve
body.
5. Attach output ports 'B1' and 'B2' to test lines. Check
that all ports are used.
6. Set supply line pressure to 170 ± 3.5 bar
(2 465 ± 50 lbf/in²).
7. Set pilot supply pressure to 170 ± 3.5 bar
(2 465 ± 50 lbf/in²).
8. Return line pressure during this test is not to exceed
0.34 bar (5 lbf/in²).
9. Test valve with 10W hydraulic oil at 50° ± 6° C
(120° ± 10° F).
Setting Manual and Pilot Pressure
1. Install actuator base (3) and secure to valve using
capscrews, washers and nuts. Torque tighten
capscrews to 20 - 21 Nm (180 - 190 lbf in). Install pivot
pin (2) in actuator base (3) by itself without installing
pedal assembly (1).
2. By taking a screw driver or pry bar and placing it
under pivot pin (2) and on top of adjusting screw (4),
you will be able to actuate the piston. See Fig. 8.
3. Gradually apply pressure to check for leaks. Make
sure adjusting screw (4) is screwed all the way down
on the threads.
4. Adjust adjusting screw (4) up (anticlockwise) in
small increments until the output pressure is
138 ± 6.9 bar (2 000 ± 100 lbf/in²) at port 'B1' with
adjusting screw (4) contacting actuator base (46) (fully
actuated). See Fig. 8. Fine adjustment will require only
turning the screw in 1/8 turn increments.
5. Cycle valve 50 times using pilot apply.
6. Actuate valve as quickly as possible. The output
pressure must reach 138 ± 6.9 bar (2 000 ± 100 lbf/in²)
within 1.0 seconds. Measurement of time begins the
moment force is applied to move the piston.
7. With the input pressure supplied, check internal
(tank) leakage of the valve at zero output pressure and
full manual apply pressure. At zero output pressure,
the valve must not pass more than 50 cc/min, through
each tank port. At full regulated pressure, the valve
must not pass more than 75 cc/min, through each tank
port. If leakage is greater than specified, rebuild of the
valve will be required.
8. Recheck regulated output pressures after cycling. If
they have changed, readjust.
9. Apply Loctite 290 to the threads of the adjusting
screw (4). Leave valve for a minimum of two minutes
to allow Loctite to cure.
Note: Use a syringe to apply Loctite to threads of
screw. Do not allow Loctite to spill over onto outer
diameter of piston. If Loctite is allowed to set up
between piston and piston guide it can result in a stuck
valve.