HYDRAULIC SYSTEM 777 SERVICE MANUAL
2-26 Published 10-01-2012, Control # 045-08
8. With all control handles in off, start engine and allow it to
idle.
Have one person bleed pressure senders (step 9)
while a second person checks pressures (step 10).
9. Bleed pressure senders:
a. Observe oil flowing from bleed line at each pressure
sender (Figure 2-27).
b. Close valve in each bleed line when clear oil flows
(no air bubbles in oil).
NOTE: Oil may not flow from bleed line for boom hoist
cylinder pressure sender until Initial Start-Up steps
14 and 15 are performed.
10. In operator’s cab, check pump pressures for following
pumps: each load drum, boom hoist, swing, left and right
travel (see Diagnostic Display Readings in Section 10 of
this manual).
• Pressures must be checked during first minute of
operation.
• Make sure pressure reading for each pump is 200 – 500
psi (13.8 – 34.5 bar).
If pump pressures are not within acceptable range, stop
engine immediately. Determine cause and correct.
NOTE: Boom hoist pressure may be less than specified
above for the first few minutes because the pump
will be filling and extending the cylinders.
Hydraulic tank level will lower rapidly as
cylinders fill. Keep tank level above LOW
LEVEL mark at all times.
It may be necessary to stop the engine periodically
as the cylinders extend to fill the tank. Do not
overfill the tank, or it will overflow when the boom
hoist cylinders are retracted. Pressure will
gradually rise as the cylinders fill with oil, and the
cylinders will stop extending part way out in their
strokes.
11. While boom hoist cylinders are extending, turn
supercharge relief valve screw (Figure 2-26) in
(clockwise) until pressure on gauge reads 75 – 100 psi
(5.2 – 6.9 bar). Tighten nut once proper pressure is
obtained.
12. With engine at idle, move boom hoist lever to DOWN
position to fully extend boom hoist cylinders.
Monitor tank level as described earlier and make
sure boom hoist charge pressure stays within 200 –
250 psi (13.8 – 17.2 bar) during this step.
NOTE: The tank low level alarm should come on when the
cylinders are fully extended. If the alarm does not
come on, determine cause and correct.
13. Once boom hoist cylinders are fully extended, make
sure tank level is not lower than LOW LEVEL mark.
14. Move boom hoist lever to UP position to fully RETRACT
boom hoist cylinders.
NOTE: Oil should start to flow from bleed line for boom
hoist cylinder pressure sender as Initial Start-Up
steps 14 and 15 are performed. Close valve in
bleed line when clear oil flows (no air bubbles in
oil).
15. Repeat steps 12 – 14 one more time.
16. Stop engine.
17. Remove bleed lines from couplers at pressure sender
manifold (Figure 2-27). Install dust caps over couplers.
18. Remove gauge from coupler at supercharge relief valve
(Figure 2-26). Install dust cap over coupler.
19. Do not reconnect electrical plugs to brake valves at this
time. Electrical plugs will be reconnected later in
procedure.
NOTE: Manitowoc Shop Personnel — pressures and
speeds noted in remaining procedures and any
adjustments you make to correct them must be
recorded in RECORD OF INSPECTION form for
crane you are working on.
Controls Calibration
1. Calibrate pressure transducers, if not already done.
2. Engage swing lock.
3. Start and run engine at high idle.
4. Depress and hold swing holding brake switch (on swing
handle) for ONE MINUTE.
5. Repeat steps 3 and 4 a second time.
Pressure Adjustments
Charge Pressure Checks
NOTE: Charge pressure can also be monitored on the
diagnostic screen for each function. Charge
pressure shown on the diagnostic screens can vary
CAUTION
Equipment Damage!
Pump pressures displayed in operator’s cab must be
checked during first minute of operation. If pressure for
any pump is less than 200 psi (13.8 bar) or greater than
500 psi (34.5 bar), shut down engine immediately to
prevent pump damage. Troubleshoot system to
determine cause of problem.
To Next Page
Loading...
Need help?
General
