Manitowoc National Crane NBT40 Series, Service Manual

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National Crane
Published 8-01-2017 Control # 287-11
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NBT40 SERVICE MANUAL BOOM MAINTENANCE
14. Extend and retract the boom and jib to ensure proper
alignment of jib stow brackets.
15. Install jib stow pins and remove jib pins. Always save
shims to allow future adjustment of jib stow if required.
Jib Jack Service and Maintenance
Important: Use only a good grade hydraulic jack oil,
transmission oil, or turbine oil. Avoid mixing types of oil.
Do not use brake fluid, alcohol, glycerin, detergent
motor oil, or dirty oil. Improper fluid can cause serious
internal damage to the jack rendering it inoperative.
Remove the jack (1, Figure 4-29) from the jib boom (2) by
removing three bolts and flatwashers (3, Figure 4-29).
Adding Oil
1. With saddle fully lowered and piston depressed, set jack
in its upright level position and remove oil filler plug. (4,
Figure 4-32).
2. Fill until oil is level with filler plug hole.
Changing Oil
1. For best performance and longest life, replace the
complete oil supply at least once a year.
2. To drain the oil, remove the filler plug (4, Figure 4-32.
3. Lay the jack on its side and allow the oil to run out into
suitable drain pin. The oil will run slowly because air
must enter as oil drains out.
4. Be careful to prevent dirt or foreign matter from entering
the system.
5. Replace with proper oil as described above.
Lubrication
Add proper lubrication oil to all pivoting sections every three
months.
Rust Prevention
Check ram every three months for any sign of rust or
corrosion. Clean as needed and wipe with an oil saturated
cloth.
NOTE: Note: When not in use, always leave the saddle
and ram all the way down.
Troubleshooting
FIGURE 4-32
3
2
1
7462-30
4
Symptom Possible Cause(s) Corrective Action
Will not lift load 1. No oil in system
2. Release valve not closed 1. Add oil to reservoir tank through oil filler hole
2. Turn handle clockwise tightly
Will lift load only part way Oil level low Add oil to reservoir tank through oil filler hole
Will lift load but will not
hold 1. The following valve or valves leaking:
a. Suction valve
b. Delivery valve
c. Release valve
2. Packings worn out or defective
1. Replace jack
2. Replace jack
Jack will not lower Release valve stuck, probably dirt or foreign matter Transfer load then replace dirty oil, flush oil reser-
voir with kerosene
Poor lifting 1. Dirty oil
2. Air in hydraulic system 1. Change hydraulic oil
2. Purge air from system
Poor pumping action Oil seal for pump unit worn out or defective Replace jack
Reference Only