Crawler cranes are vital machines in the construction and industrial sectors, responsible for lifting and moving heavy loads. One critical component of crawler cranes is the track shoe, which plays a crucial role in providing stability and traction for the machine’s movement. However, track shoe derailment can occur, leading to operational disruptions and potential safety hazards. In this passage, we will explore the causes of crawler crane track shoe derailment and outline recovery measures to address such incidents.
The Causes of track shoe derailment
The causes of crawler crane derailment can be divided into internal and external factors
The Internal Factors Of Track Shoe Derailment
Two specific mechanical conditions must be met for the crawler crane track shoe to derail: an increase in lateral forces acting on the track shoes and a decrease in the vertical forces exerted on them.
Increase in Lateral Forces
When the lateral forces acting on the track shoes become excessive, they can cause the track shoes to deviate from their intended path and potentially derail. Factors contributing to increased lateral forces include track misalignment, uneven weight distribution, turning or traversing on inclined surfaces, and operating at high speeds or making sudden changes in direction. These conditions put additional stress on the track shoes, increasing the risk of derailment.
Decrease in Vertical Forces
Adequate vertical forces are essential to maintain proper contact between the track shoes and the tracks. A decrease in vertical forces can lead to reduced stability and an increased risk of derailment. Factors that can contribute to a decrease in vertical forces include insufficient load distribution, overloading, worn or damaged suspension components, and inadequate tire pressure. These conditions can result in uneven weight distribution and inadequate support for the track shoes, compromising their ability to stay on the tracks.
The external factors of track shoe derailment
External factors contribute to crawler crane track shoe derailment by affecting the mechanical conditions required for proper functioning. These factors include:
Changes in the crane's metal structure
Any alterations or deformations in the crane’s metal structure can lead to misalignment between the track shoes and the tracks. This misalignment increases the risk of derailment.
Abnormalities in the braking system:
When the crane’s braking system experiences abnormalities, such as uneven braking on one side, it can disrupt the balance and stability of the track shoes during crane movement. This imbalance can lead to derailment.
Failure to clear foreign objects on the tracks
If foreign objects, like debris or obstacles, are not promptly cleared from the tracks, they can interfere with the smooth movement of the track shoes. This interference can cause the track shoes to deviate and potentially derail.
External impacts on the crane's gantry
External impacts, such as collisions or being struck by objects, can affect the alignment and stability of the track shoes. These impacts can introduce forces that lead to derailment.
Inadequate precautions during a typhoon
Insufficient measures taken during the passage of a typhoon can expose the crane to strong winds and adverse conditions. These conditions can exert lateral forces on the crane, increasing the risk of track shoe derailment.
Encountering gusts of wind during operations
Strong gusts of wind during crane operations can introduce lateral forces that exceed the designed limits. These forces can destabilize the track shoes and contribute to derailment incidents.
the recovery measures of track shoe derailment
To address crawler crane track shoe derailment effectively, it is essential to implement appropriate recovery measures. Here are the recommended steps:
First-Confirm the possibility of crane overturning
Confirming the possibility of crane overturning is a crucial step in the recovery process following a track shoe derailment. This assessment is necessary to ensure the safety of personnel and prevent further damage or accidents.
If there is a risk of the crane overturning, the first priority is to evacuate on-site personnel promptly and, if possible, relocate nearby cranes.
If the crane exhibits tilt and the derailed gantry causes the ground to sink, indicating an inclination towards overturning, appropriate measures must be taken immediately to secure or prevent further sinking of the ground. This is crucial to prevent any further tilting or potential overturning of the equipment.
If there is no immediate risk of overturning after the crane derailment or suitable measures have been implemented to prevent overturning, personnel and tools should be organized promptly to restore the crane to its original position.
Second-Confirm if the site is ready for derailment recovery
Before initiating any recovery efforts, it is essential to assess the condition of the site and evaluate the readiness for resuming crane operations. This assessment involves several key considerations:
Ground and track damage
Evaluate the extent of damage caused to the ground and crane tracks during the derailment. Assess if the ground is stable and capable of supporting the crane’s weight once it is back on track. If significant damage is present, it may be necessary to arrange for repairs or reinforcement before proceeding with the recovery.
Weather conditions
Monitor the prevailing and forecasted weather conditions. If adverse weather, such as strong winds, heavy rain, or a typhoon, persists or is expected to worsen, it may be prudent to postpone the derailment recovery until the weather improves. Unfavorable weather conditions can compromise the safety of the recovery operation and potentially lead to further incidents.
Finally- track shoe derailment recovery
Once the derailment equipment and site conditions have been confirmed, the recovery work should be immediately initiated while ensuring the equipment remains stable and does not overturn. The specific steps are as follows:
step 1-Preparation of Technical Personnel
Convene a pre-work meeting with relevant technical personnel to clarify the responsibilities of the on-site supervisor, safety officer, construction workers, and construction units. Develop construction plans, schedules, and emergency handling procedures. All personnel involved in the project should have a clear understanding of their responsibilities and prepare the necessary tools in advance.
Step 2-Tool Preparation
Prepare appropriate tools based on the site conditions, considering factors such as the weight of the equipment and the distance of displacement.
- Lifting and jacking tools: 50-ton truck crane, 16-ton forklift (1 each), 5-ton manual chain hoist, 10-ton manual chain hoist, steel wire ropes, shackles, six 320-ton hydraulic jacks, two sets of 200-ton jacks and hydraulic pump stations, steel beams, jack stands, and several blocking pads.
- Carbon planing and welding tools: welding machine, carbon planer, oxygen-acetylene equipment, cutting tools, several grinding tools. Additionally, prepare an adequate quantity of E5015 welding rods, welding rod insulation containers, 6mm carbon rods, and paint.
- Guiding and auxiliary tools: several No. 20 and No. 40 I-beams, several No. 20 channel steels, several 5-ton lifting lugs, approximately 40 square meters of steel plates with thicknesses of 10mm, 16mm, and 20mm, and adjustment wedges as per the site conditions.
Step 3-Retract tack shoe
After aligning the track shoe with the rail, the stabilization and securing process becomes crucial to ensure its stability and prevent any future movement. Here are additional steps for repairing the track shoe derailment:
Shimming
Use shims or blocking material to provide additional support and stability to the track shoe. Insert shims between the base of the track shoe and the underlying ballast or substructure. Shims help distribute the load evenly and prevent any rocking or shifting of the track shoe.
Blocking
Place blocking material, such as wooden or steel blocks, around the track shoe to further stabilize it. These blocks should be strategically positioned to support the track shoe and prevent any lateral movement. Ensure that the blocking is securely in place and tightly packed to provide maximum stability.
Fastening
Securely fasten the track shoe to the rail using appropriate track spiking tools or other fastening methods. Track spikes, also known as rail spikes or cut spikes, are commonly used to fasten the track shoe to the rail. Use a spike maul or spike driver to drive the spikes through the holes in the track shoe and into the rail. Ensure that the spikes are driven in at the correct angle and depth to achieve a secure connection.
