Manitowoc National Crane NBT30H-2, Service Manual

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HYDRAULIC SYSTEM NBT30H-2 SERVICE MANUAL
2-10
03-20-2019 Control # 613-06
8. Connect the outrigger return line and retract the
outrigger. Replenish the reservoir hydraulic oil level as
necessary.
9. Repeat step 7 and step 8 for the remaining outriggers.
10. Disconnect the return lines from a pair of outrigger
cylinders and activate the cylinders to their maximum
down positions.
11. Connect the return lines and raise the outrigger
cylinders to the stowed position. Replenish the reservoir
hydraulic oil level as necessary.
12. Repeat step 10 and step 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. Working reservoir capacity
(capacity to full mark) is 276 liters (73 U.S. gallons). 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.
• To remove entrapped air from telescope cylinders, lower
the boom to below horizontal and fully telescope the
boom in and out several times.
• If the air is still trapped, lower the boom to below
horizontal, extend the telescope cylinders as far as
practical, and allow the boom to remain in this position
overnight. This should allow trapped air to find its way to
the holding valve so that telescoping the boom IN the
next morning should force the air back to the reservoir.
Ensure the boom is first telescoped IN (not OUT) in the
morning. Telescoping OUT may cause air to be forced
back into a cylinder.
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.
WARNING
Tipping Hazard!
Extending the boom at low angles greatly increases the
risk of tipping. Locate the crane on a firm surface and
position the boom over the front on outriggers.
!