Crane Failure and Troubleshooting 2: Unit Article

In the crane use process, mechanical parts, components, electrical control and hydraulic system components will be worn and lead to failure. Possible causes for the same fault are not one to one corresponding relationship. So in order to make serious analysis of fault and accurately find the real cause of the malfunction, and take elimination method corresponding to the exclusion of the fault point to restore the technical performance.

Lifting crane unit article failure and troubleshooting

A. Rolling bearing failure and reason:

• High temperature.
• Abnormal sound.
• The metal grinding noise.
• Shock sound.

The causes:

• Lubricating oil dirt, lacking in oil or too much oil.
• Bearing dirty.
• Lacking in oil.
• Rolling body damage.
• Solving method:
• Remove dirt, replace bearing, and check the number of oil.
• Remove dirty.
• Add oil.
• Replace bearing.

B. Brake failure and reason:

1. Cannot block the brake wheel (weight decline).

The causes:

• (1) The hinge is stuck.
• (2) There is oil dirt on brake wheel and friction plate.
• (3) There is no enough journey for electromagnet core.
• (4) Brake wheel or friction plate has serious wear.
• (5) Main spring loose and damage.
• (6) The locking nut and pull rod loose.
• (7) The impeller rotation of hydraulic brake is not working.

Solving method:

• (1) Remove stuck fault.
• (2) Clean the oil dirt.
• (3) Adjust brake.
• (4) Replace friction plate.
• (5) Replace friction plate.
• (6) Tighten the lock nut.
• (7) Maintain promoting mechanism and electrical.

2. Brake can’t be loosed.

The causes:

• (1) Electromagnet coil burn out.
• (2) Electromagnet wire is disconnected.
• (3) Friction plate adhesion on the brake wheel.
• (4) The movable hinge is stuck.
• (5) Main spring force is too large or too much weight.
• (6) The brake push rod bend, and it can’t push electromagnet.
• (7) The improper use of oil.
• (8) Impeller is stuck.
• (9) The voltage is lower than the rated voltage 85%, the electromagnet force shortage.

Solving method:

• (1) Replacement.
• (2) Connect the wire.
• (3) Clean with kerosene.
• (4) Remove stuck phenomenon, lubrication.
• (5) Adjust the main spring force.
• (6) Straightening the top rod or change the top rod.
• (7) Replace oil according to the working environment temperature.
• (8) Adjust the push mechanism and inspect electrical parts.
• (9) Identify the voltage drop reasons, troubleshooting.

3. Brake fever, friction plate has scorched flavor and wear very quickly.

The causes:

• (1) After brake shoe release, there is no uniform away from the brake wheel, result in friction.
• (2) Two sets brake shoe and the brake wheel clearance is uneven or gap is too small.
• (3) The short stroke brake auxiliary spring is damaged or bent.
• (4) The surface of brake wheel is rough.

Solving method:

• (1) Adjust the gap.
• (2) Adjust the gap.
• (3) Replace or repair the auxiliary spring.
• (4) According to the requirements to turning brake wheel surface.

4. Brake is easy to leave the adjusting position, brake torque is not stable.

The causes:

• (1) Adjusting nut and back nut is loose.
• (2) The screw thread damage.

Solving method:

• (1) Tighten nut.
• (2) Replacement.

5. Electromagnet fever or has sound.

The causes:

• (1) The main spring force is too large.
• (2) Lever system is stuck.
• (3) Armature and iron core joint position is not correct.

Solving method:

• (1) Adjust to the appropriate size.
• (2) Eliminate the cause of stuck, lubrication.
• (3) Scrape fitting surface.

C. Reducer failure and reason:

1. Periodic gear chatter, especially for the driven wheel
The causes:

• Pitch error is too large
• Solving method:
• Repair and reinstall

2. Sharp metal friction sound, reducer vibration, casing jingle

The causes:

• (1) The transmission gear gap is too small, the two gear shaft is not parallel, and the tooth top has sharp edge.
• (2) Gear working surface is not flat

Solving method:

• (1) Repair and reinstall
• (2) Repair and reinstall

3. When gear meshing, there is uneven knock sound and casing vibration

The causes:

• Gear isn’t along the whole gear tooth contact, but in one corner
• Solving method:
• Replace gear

4. The shell heating, especially for the installation position of bearing

The causes:

• (1) Bearing broken
• (2) The shaft stuck
• (3) Gear wear
• (4) Lack of lubrication oil

Solving method:

• (1) Replace bearing
• (2) Replace bearing
• (3) Replace gear
• (4) Add lubrication oil

5. Section surface spill oil

The causes:

• (1) Seal failure.
• (2) The housing deformation.
• (3) Section surface uneven.
• (4) Connection bolt loose

Solving method:

• (1) Replace seal
• (2) Repair section surface, serious deformation is replaced.
• (3) Shovel the section
• (4) Clean the oil return groove, fasten bolt.

6. Reducer vibrate on the base

The causes:

• (1) The anchor bolts loose.
• (2) Axis isn’t concentric connecting with other parts.
• (3) The base rigidity is bad.

Solving method:

• (1) Adjust anchor bolt
• (2) Adjust line
• (3) Reinforcement base, increase rigidity

7. Reducer overall heating

The causes:

• Excessive lubrication oil
• Solving method:
• Adjust the amount of oil
• D. Sliding bearing failure and reason:
• Excessive heating

The causes:

• (1) Bearing deflection or too tight
• (2) Improper clearance
• (3) Lack of lubricant
• (4) Lubricant quality is not qualified

Solving method:

• (1) Eliminate the deviation, reasonable fastening
• (2) Adjust the gap
• (3) Add lubricant
• (4) Replace the qualified lubricant

E. Crane traveling mechanism failure and reason:

Bridge running is skew and gnaw rail
The causes:

• (1) Two drive wheel diameter error is too large
• (2) Drive wheel isn’t completely contact with rail
• (3) Drive wheel axis isn’t upright
• (4) The metal structure has deformation
• (5) The quality of rail installation is poor
• (6) The rail top has oil or frost

Solving method:

• (1) Measure, processing, and replace wheel
• (2) Increase the diameter of drive wheel
• (3) Examine and eliminate axis deviation phenomenon
• (4) Correct the structure
• (5) Adjust the rail to meet the installation technical conditions
• (6) Eliminate oil bad frost

F. Trolley traveling mechanism failure and reason:

1. Trolley slip

The causes:

• (1) The rail top has oil
• (2) Wheel pressure is uneven
• (3) Two rail elevation difference is too large in the same section
• (4) The braking is too violent

Solving method:

• (1) Remove
• (2) Adjust the wheel pressure
• (3) Adjust the rail to meet the technical conditions
• (4) Improve the motor starting method and choose the winding motor

2. Trolley run with three legs

The causes:

• (1) The wheel diameter error is too large.
• (2) Installation is unreasonable.
• (3) Trolley frame has deformation.

Solving method:

• (1) Process according to the requirements of the drawing.
• (2) Adjust the installation according to the technical conditions.
• (3) Correct the structure.

3. When starting, trolley body twist

The causes:

• (1) The trolley wheel pressure is uneven or a drive wheel suspend.
• (2) Gnaw rail.

Solving method:

• (1) Adjust the trolley three legs phenomenon.
• (2) Solve the gnaw rail phenomenon.

G. Rail clamping device failure and reason:

Brake torque is small, and it can’t hold the rail
The causes:

• (1) The movable hinge is stuck and the lubrication is bad.
• (2) Brake belt wear and brake torque decrease observably.

Solving method:

• (1) Cleaning and lubrication.
• (2) Replace the wear parts.

Related information on lifting crane failure and troubleshooting

Crane Failure and Troubleshooting 1：Part Article
Crane Failure and Troubleshooting 2: Unit Article
Crane Failure and Troubleshooting 3: Electrical Equipment Article 
Crane Failure and Troubleshooting 4: Electric Control Article