What are the Common Reasons for a Tower Crane to Rotate Slowly and Weakly?

Tower cranes are essential pieces of equipment in construction projects, providing the means to lift and move heavy loads to various heights. A critical component of a tower crane is its slewing mechanism, which allows the crane to rotate on its axis. When a tower crane experiences slow or weak rotation, it can significantly impact the efficiency and safety of construction operations.

This article will delve into the common causes of this issue and provide potential solutions.  

Components of the Slewing Mechanism of a Tower Crane

The slewing mechanism of a tower crane is a complex system that enables the horizontal rotation of the crane’s superstructure. The slewing gear, a large toothed wheel, is directly connected to the crane’s body. It receives the rotational force from the drive mechanism, which is typically powered by an electric motor. The frequency converter controls the speed and torque of the electric motor, allowing for precise control of the slewing motion.

The gearbox reduces the high-speed rotation of the motor and increases the torque, ensuring that the slewing gear can effectively drive the heavy crane structure. The brake is used to bring the slewing motion to a stop or to hold the crane in a specific position.

1. Slewing bearing: This is the central component that supports the weight of the tower and jib and allows for rotation.  
   1. Slewing drive: Provides the power for rotation, typically driven by a hydraulic motor or electric motor.  
   1. Gearbox: Reduces the speed of the slewing drive and increases the output torque.
   1. Brake: Controls the starting, stopping, and holding of the slewing motion.
   1. Control system: Regulates the operation of the slewing mechanism, including speed, direction, and braking.

How the Slewing Mechanism Works:

A tower crane is a commonly used construction machine that primarily lifts and transports materials using a crane arm and hook. The slewing mechanism is the component that controls the crane’s horizontal rotation. It works by utilizing a slewing gear to transmit torque, which is then used to drive the entire mechanism to rotate.

The driving torque is provided by an electric motor. This torque is transmitted through a gearbox to the slewing gear and rack. The meshing of the gear and rack transfers the driving torque, enabling the tower crane to rotate.

Common Causes and Solutions for Slow and Weak Tower Crane Rotation

When a tower crane experiences slow or weak rotation, its slewing mechanism often signals an issue. Let’s analyze common faults in this mechanism and explore potential solutions.

No.	Tower Crane Fault	Possible Cause	Solution
1	Slow and weak rotation	Insufficient fluid in the fluid coupling; Fluid leakage leading to insufficient oil and low efficiency	Fill the fluid coupling according to the requirements; Check for leaks and replace failed seals
2	Slewing mechanism cannot rotate	Failure of the slewing motor or electrical system; Fluid coupling not filled or damaged; Slewing brake not released; Slewing limit switch activated	Inspect and troubleshoot; Fill or replace; Inspect and troubleshoot; Adjust
3	Slewing brake failure	Electrical fault; Brake disc rusted and stuck	Inspect and troubleshoot; Inspect and clean
4	Abnormal noise during slewing	Lack of lubrication; Loose connection bolts	Add lubricant; Check and tighten
5	No slewing brake	Brake switch failure; Brake circuit fault; Burnt brake coil	Repair or replace; Tighten terminals, replace wire
6	Frequent breakage of luffing ropes	Uneven rope winding on the drum; Loose luffing ropes	Rewind the ropes; Adjust and tighten

Common Fault Phenomena

1. Power System Failures

• Motor failures: Motor overload, burnout, or circuit faults can lead to insufficient power output, affecting slewing speed.
• Hydraulic system failures: Failures in the hydraulic pump, valves, or hoses can result in low hydraulic oil pressure, reducing the output torque of the hydraulic motor.
• Gearbox failures: Gearbox wear, gear damage, or poor lubrication can decrease transmission efficiency, impacting slewing speed and torque.

2. Structural Problems

• Slewing bearing wear: Severe wear of the slewing bearing can increase rotational resistance, affecting slewing speed.
• Insufficient counterweight: Insufficient counterweight can cause the slewing system to be unbalanced, affecting slewing speed and stability.
• Structural deformation: Deformation of the tower or jib can increase rotational resistance, affecting slewing speed.

3. Control System Failures

• Electrical control system failures: Control circuit faults or sensor failures can lead to abnormal slewing control signals, affecting slewing speed and torque.
• Hydraulic control system failures: Hydraulic control valve failures or hydraulic oil contamination can affect the control precision of the hydraulic system, impacting slewing performance.

4. External Factors

• Excessive load: Exceeding the rated load can cause motor overload, affecting slewing speed.
• Strong winds: Strong winds can increase rotational resistance, affecting slewing speed.
• Extreme temperatures: Extreme temperatures can affect the viscosity of hydraulic oil, impacting the performance of the hydraulic system.  

Troubleshooting and Solutions

• Regular inspections and maintenance: Regularly inspect and maintain components such as motors, hydraulic systems, gearboxes, and replace worn parts promptly.  
• Adjust counterweights: Adjust counterweights according to the load to ensure the slewing system is balanced.
• Inspect control systems: Inspect electrical and hydraulic control systems to identify and rectify any faults.
• Eliminate external influences: Avoid overloading the crane and stop operation in strong winds.

Final Words: CPTC – Your Best Tower Crane Parts Partner

CPTC, a leading provider of tower crane parts, offers a comprehensive range of slewing mechanisms. These vital components play a crucial role in enabling precise rotational movement and positioning across diverse industrial applications. Slewing mechanisms from CPTC integrate centrifugal fans, flexible coupling rubbers, slewing motors, reducers, rings, and specialized slewing devices, ensuring reliable and efficient operation in tower cranes and other equipment.