Manitowoc National Crane NBT30H-2, Service Manual

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2
National Crane
03-20-2019 Control # 613-06
2-25
NBT30H-2 SERVICE MANUAL HYDRAULIC SYSTEM
Troubleshooting Chart
CONDITION ITEM POSSIBLE CAUSE POSSIBLE SOLUTION
Excessive Noise and/
or Vibration
Check fluid level in reservoir.
Insufficient hydraulic fluid causes
cavitation.
Fill the reservoir to proper level.
Check for air in system.
Air in system causes noisy,
erratic control. Purge air and tighten fittings.
Check inlet for leaks.
Check pump inlet pressure/
vacuum.
Improper inlet conditions cause
erratic behavior and low output
flow.
Correct pump inlet pressure /
vacuum conditions.
Inspect shaft couplings.
A loose or incorrect shaft
coupling causes excessive noise
and/or vibration. Repair or replace coupling and
ensure that correct coupling is
used.
Check shaft alignment.
Misaligned shafts create
excessive noise and/or vibration.
Correct shaft misalignment.
Hydraulic fluid viscosity above
acceptable limits.
Hydraulic fluid viscosity above
acceptable limits or low fluid
temperature will not allow the
pump to fill or operate properly. Allow system to warm up before
operating, or use fluid with the
appropriate viscosity grade for
expected operating temperatures.
Actuator Response is
Sluggish
Check external system relief
valve setting. Low external relief valve setting
slows down system.
Adjust external relief valve setting
following manufacturer’s
recommendations. External relief
setting must be above pressure
compensation setting to operate
properly.
Check pressure compensation
and load sense control setting.
Low pressure compensation
setting prevents the pump from
achieving full stroke. Low load
sense setting limits output flow.
Adjust pressure compensation
and load sense settings.
Check load sense control
signal pressures.
Incorrect load sense signal will
not allow pump to operate
correctly. Inspect system to ensure that
proper load sense signal is
transmitted to the pump.
Internal system leaks.
Worn internal parts don’t allow
the pump to operate properly. Refer to local distributor for
required repair.
Hydraulic fluid viscosity above
acceptable limits.
Hydraulic fluid viscosity above
acceptable limits or low fluid
temperature will not allow the
pump to fill or controls to operate
properly.
Allow system to warm up before
operation or use fluid with the
appropriate viscosity grade for
expected operating temperatures.
Check external system valving.
Malfunctioning valve(s) may not
allow system to respond
properly.
Repair or replace system valve(s),
as required.
Check pump case pressure.
High case pressure causes the
system to be sluggish. Correct case drain line
restrictions.
Check pump inlet pressure/
vacuum. High inlet vacuum causes low
output flow.
Correct inlet pressure conditions.