Crawler cranes are robust machines widely used in construction and heavy lifting operations. However, like any complex equipment, they can encounter faults and malfunctions. One common issue is running deviation, where the crane tends to veer off course during movement. In this blog, we will analyze the possible causes of crawler crane running deviation and discuss appropriate solutions to address these problems.
the example of crawler crane running deviation
During a construction project, a crawler crane is being used to lift and transport heavy loads across the construction site. However, the crane operator notices a consistent right deviation during forward movement. When the crane moves in reverse, there is no deviation, and the crane maintains a straight path. Additionally, when the crane accelerates while moving forward, the deviation becomes more pronounced.
The operator attempts to compensate for the deviation by making continuous adjustments to the controls, but the issue persists. The right deviation poses a significant challenge as it affects the crane’s ability to accurately position loads and maintain a straight path, potentially causing delays and safety concerns.
The reason of this example
To address the crawler crane running deviation, the operator reports the issue to the maintenance team. They conduct a thorough inspection of the mechanical and hydraulic components of the crane, including the drive wheels, guide wheels, tracks, motor, control handle, main valve, and brake valve. Through this inspection, they aim to identify the specific cause of the deviation.
After careful examination, the maintenance team discovers that the brake valve’s valve spool controlling the forward direction is partially stuck, resulting in reduced hydraulic flow and pressure on the right side of the crane during acceleration. This hydraulic imbalance causes the crane to veer to the right during forward movement.
the solution of this example
To resolve the issue, the maintenance team cleans the valve spool and ensures smooth movement without any obstructions. They conduct additional tests to verify that the running deviation has been eliminated. Once the repairs are complete, the crane is able to move forward without deviation and maintain a straight path during acceleration, ensuring safe and efficient crane operations on the construction site.
crawler crane running deviation reasons
Crawler crane undercarriage
The undercarriage of a crawler crane is made up of mechanical components including track shoes, track rollers, idlers, and sprockets. It is important to maintain parallel tracks and ensure the alignment of the wheel centerlines. However, since the described deviation occurs exclusively during forward movement and not during backward movement, mechanical component issues can be ruled out as the cause. This directs our attention to investigating the hydraulic system as the potential source of the deviation.
The apperance of undercarriage running deviaton
When a crawler crane experiences undercarriage faults causing running deviation, it can exhibit several observable appearances:
Misalignment of Tracks
A visible misalignment of the tracks can be observed, where one track appears to be positioned at a different angle or distance compared to the other. This misalignment can cause the crane to deviate from its intended path during forward movement.
Abnormal Track Tension
The tension in the tracks may vary between the left and right sides. Unequal tension can affect the stability and alignment of the undercarriage, leading to crawler crane running deviation during crane operation.
Hydraulic Components
The hydraulic system plays a vital role in the operation of crawler cranes. Several components, including the motor, control handle, main valve, and brake valve, can contribute to running deviation if they malfunction.
Motor
Excessive internal leakage in the motor can result in reduced volumetric efficiency, causing the right motor to rotate at a slower speed compared to the left motor. However, since the described deviation occurs only during forward movement and the motor is unlikely to cause such selective deviation, we can exclude motor malfunction as a probable cause.
Control Handle
The main valve, controlled by the operator through the control handle, can experience faults such as excessive internal leakage or an unclean hydraulic system. If there is excessive internal leakage, both forward and backward movements would exhibit running deviation. However, as the described deviation occurs only during forward movement, we can reasonably conclude that the main valve's internal leakage is not the primary cause.
Brake Valve
The brake valve is responsible for controlling the brake system and ensuring smooth movement. Faults in this component, such as excessive internal leakage or improper valve spool action, can contribute to running deviation. Excessive internal leakage would cause deviation during both forward and backward movements, which is not consistent with the described situation. However, if the valve spool becomes stuck due to debris or if the internal throttling port is blocked, the valve's action may be incomplete, resulting in reduced hydraulic flow and pressure. This scenario aligns with the observed deviation during forward movement, especially when accelerating.
The solution of crawler crane running deviation
The solution to crawler crane running deviation depends on the underlying cause, which can be mechanical or hydraulic in nature. Here are some general solutions for addressing running deviation:
For Hydraulic System
- Inspect the hydraulic system for any blockages or restrictions that could affect the flow of hydraulic fluid.
- Check the hydraulic control valves for proper operation and ensure they are not stuck or malfunctioning.
- Examine the hydraulic cylinders and seals for leaks or damage, as these issues can impact the crane’s stability and cause crawler crane running deviation.
- Conduct thorough maintenance and servicing of the hydraulic system to ensure it is functioning optimally.
For undercarriage system
- Whether the two tracks are parallel
- Whether the centerlines of the track roller, guide wheels, idler, and support wheels coincide.
how to determine the two tracks parrel?
Position the Crane on Level Ground: Ensure that the crane is placed on a flat and level surface. This will provide a stable base for accurate measurements.
Measure the Distance between the Tracks: Take measurements at several points along the length of the crane to determine the distance between the inner edges of the two tracks. Ensure that the measurements are consistent and within the manufacturer’s specifications.
Check for Consistent Measurements: Measure the distance between the tracks at multiple locations, including the front, middle, and rear sections of the crane. Compare these measurements to verify if they are consistent and parallel.
Use Alignment Tools: Employ alignment tools, such as laser alignment devices or string lines, to further verify the parallelism of the tracks. These tools can help you assess the alignment visually and ensure accuracy.
