Manitowoc National Crane NBT40 Series, Service Manual

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NBT40 SERVICE MANUAL HYDRAULIC SYSTEM
National Crane
Published 8-01-2017 Control # 287-11
2-5
1. Remove the reservoir drain plug. Allow about three
minutes after hydraulic oil stops flowing from the drain
port for the side walls to drain.
2. Clean and install the reservoir plug and fill the reservoir
with a 50/50 mixture of fuel oil and clean hydraulic oil.
3. Cycle the crane through all functions several times.
Then return the crane to its stowed position and shut
down the engine.
4. Remove the reservoir drain plug and drain the reservoir.
Clean and install the drain plug and fill the reservoir with
clean hydraulic oil.
NOTE: Connect a drain hose in place of a disconnected
return line so that the hydraulic oil can be drained in
a container for proper disposal.
5. Disconnect the return line from the lift cylinder and raise
the boom to maximum elevation.
6. Connect the cylinder return line and lower the boom to
its stowed position. Replenish the reservoir hydraulic oil
level as required.
7. Disconnect the return line from an outrigger extension
cylinder and fully extend the outrigger.
8. Connect the outrigger return line and retract the
outrigger. Replenish the reservoir hydraulic oil level as
necessary.
9. Repeat Steps 7 and 8 for the remaining outriggers.
10. Disconnect the return lines from a pair of outrigger jack
cylinders and activate the cylinders to their maximum
down positions.
11. Connect the return lines and raise the outrigger jack
cylinders to the stowed position. Replenish the reservoir
hydraulic oil level as necessary.
12. Repeat Steps 10 and 11 for the remaining two outrigger
cylinders.
13. Disconnect the return line from the telescope cylinder
and fully extend the boom.
14. Connect the return line and retract the boom. Replenish
the reservoir hydraulic oil level as necessary.
15. Disconnect the return line from the hoist motor and fully
hoist up.
16. Connect the return line to the hoist motor and fully hoist
down and back up again. Replenish the reservoir
hydraulic oil level as necessary.
17. Disconnect one of the lines from the swing motor and
drive the motor in the direction it will go.
18. Connect the line to the swing motor, then drive the swing
motor in the opposite direction until the boom is centered
and forward. Replenish the reservoir hydraulic oil level
as necessary.
When hydraulic oils are changed, recheck the reservoir
hydraulic oil level after brief system operation and add
hydraulic oil as required.Ensure the crane is level and in the
travel mode of operation when the hydraulic system is being
filled. The system must be filled with all cylinders retracted.
Fill the reservoir to the full mark on the reservoir sight gauge.
After the reservoir is filled, operate all circuits and recheck
the reservoir sight gauge. Add hydraulic oil as required.
Removing Air From The Hydraulic System
Air entering the hydraulic oil is normally removed by baffles
in the hydraulic reservoir. If a component has been replaced,
the reservoir level is too low, or a leak develops in the suction
line to the pump, air can enter the system. Air can cause
noisy operation of the swing and hoist hydraulic motors.
Check the level of the hydraulic reservoir first if noisy
operation occurs. Inspect for leaks in the suction lines
leading to the pumps.
Minute leaks may be hard to locate. If a leak is not readily
detectable, use the following way to check for it:
• Seal all normal openings in the hydraulic system and the
reservoir. Using a positive means to control the pressure
(like a regulator), pressurize the hydraulic system to
13.8 - 27.6 kPa (2 - 4 psi) and inspect all joints and
fittings for evidence of leaks. A soap solution applied to
the fittings and joints may also prove helpful in detecting
minute leaks while the system is pressurized. Remove
the pressure, repair any leaks found, and reopen any
openings (such as a vent) closed for inspection. Refill
the reservoir after completing any repairs or service.
Operate all hydraulic circuits several times in both
directions.
• This action should return any entrapped air to the
reservoir where it can be removed by the internal
baffles.
CAUTION
Hydraulic oil supply lines must be connected to the
cylinders when flushing the system.
CAUTION
When draining the outrigger cylinders, always operate
either both front or both rear cylinders together to prevent
twisting the crane.
CAUTION
Hydraulic oils must be of the same specifications or
discoloration (milkiness) may occur.
Reference Only