Crawler cranes play a vital role in diverse construction and heavy lifting projects, necessitating regular maintenance for optimal performance and durability. Among the integral components within their walking system, the crawler crane idler assumes a critical position. Positioned on the undercarriage frame, its primary function involves guiding the track, ensuring its proper winding. Additionally, the idler facilitates track tension adjustments through the utilization of a tensioning device. This pivotal component contributes significantly to the smooth operation and longevity of crawler cranes, underscoring the importance of regular inspection and upkeep.
In this blog, we will explore the reasons behind guide idler wheel damage and discuss effective replacement methods. Understanding these aspects will help crane operators and maintenance personnel better care for their equipment, minimize downtime, and maximize productivity.
The working principle of crawler crane idler
The idler wheel of crawler crane is responsible for supporting the weight of the crawler crane and maintaining proper tension in the track. It is connected to the frame of the crane through a rotating shaft and rotates freely. The tensioning mechanism, such as a spring or hydraulic cylinder, helps adjust the tension in the track by moving the guide idler wheel forward or backward.
The correct positioning of the crane idler and track roller
When a crawler crane is moving uphill, the crawler crane idler is positioned in the front, while the crawler crane track roller is at the back. This arrangement increases the traction between the track and the ground, lowers the center of gravity of the crane, extends the boom fully, and ensures that the bucket teeth are perpendicular to the slope. This setup prevents the crane from sliding down suddenly and stabilizes the machine by preventing the bucket teeth from digging into the ground.
When moving downhill, the crawler crane track roller should be positioned in the front. This tightens the upper track to prevent the crane from sliding down under the force of gravity when it stops. It is also recommended to lower the speed and maintain a slow pace. The boom should be extended, and the angle between the arm and the boom should be 90 degrees. The back of the bucket should be within 30 centimeters from the ground. In case of any unexpected incidents, the bucket should be immediately lowered.
damage sign of crawler crane idler
Recognizing the signs of damage in the crawler crane idler is crucial for prompt repairs and to avoid further complications. By observing these indicators, operators and maintenance personnel can address issues before they escalate and affect the crane’s performance. Let’s explore some common signs that indicate possible damage to the idler wheel of crawler crane.
Excessive deviation in axis alignment
When the axis alignment of the crane idler is significantly out of range, it can result in track vibrations and impacts. Insufficient or no lubricating oil film may be present due to inadequate clearance between the idler shaft and the bearing sleeve.
Rough surface of the idler shaft
If the guide idler wheel shaft surface contains numerous metal peaks, it can disrupt the integrity and continuity of the lubricating oil film between the shaft and the sliding bearing. This leads to increased metal debris in the lubricating oil, further roughening the shaft and bearing surfaces and causing severe wear.
Structural defects
The lubricating oil is typically injected into the idler through a threaded plug hole at the shaft's end, gradually filling the entire cavity. Without a dedicated oil injection tool, it becomes challenging for the lubricating oil to flow through the complex cavity inside the crane idler solely under the influence of gravity. This can result in insufficient lubricating oil and inadequate gas discharge within the cavity, leading to oil shortages.
Lack of oil passage
The absence of an oil passage in the clearance between the idler shaft and the bearing sleeve has detrimental consequences. Without proper oil flow, heat generated during operation cannot dissipate effectively, leading to increased working temperatures. This, in turn, causes a decrease in lubricating oil viscosity and a reduction in the thickness of the oil film. As a result, friction and wear between the idler shaft and the bearing sleeve escalate, potentially leading to premature failure. Regular maintenance and inspection of the idler's lubrication system are crucial to ensure adequate oil flow, preventing these damaging effects.
The Replacement Methods Of crane idler
When the aforementioned damage signs are detected in the idler wheel of crawler crane, it indicates the need for idler replacement. Here are the methods for replacing the crane idler:
First-Preparation
Before replacing the idler on the crane, gather all the necessary tools and equipment, such as wrenches, power drills, adjustable wrenches, grinders, files, hammers, screwdrivers, and oil brushes. Prior to the disassembly process, it is crucial to ensure that the surface of the idler is thoroughly cleaned to prevent any debris or contaminants from entering the interior components, which could potentially cause damage.
Second-Disassembling the crane idler
The disassembly of the idler is a vital part of the crane’s replacement process, allowing for thorough inspection, identification of issues, and the subsequent repairs or replacements required to ensure optimal performance and safety.
Step 1
Use a wrench to carefully compress the steel balls, allowing for their removal from the edge of the idler. Take caution during this step to avoid any accidental injury or damage to the surrounding components.
Step 2
Utilize a power drill to carefully unscrew the nut securing the idler. Remove the dust cover and proceed with disassembling the bearing, ensuring that all parts are handled with care to avoid any mishaps.
Step 3
With the assistance of pliers, remove the fastening screws located on the edge of the drive wheel. Once the screws are loosened, employ a wrench to detach the wheel from its position, ensuring a smooth and controlled process.
Finally-Installing the crane idler
- Position the edge of the drive wheel back onto the axle, ensuring proper alignment. Secure the wheel in place by tightening the fastening screws using the appropriate tools.
- Insert the bearing into the inner part of the wheel, applying a sufficient amount of lubricating oil beforehand for smooth operation. Tighten the bearing by using a nut, ensuring it is securely fastened.
- Follow the specific instructions provided by the manufacturer to install the steel balls. Carefully compress the steel balls into their designated locations, ensuring they are properly seated within the idler.
Precautions
- Safety should always be a top priority during the entire replacement process. Adhere to all safety guidelines and wear appropriate personal protective equipment to minimize any potential risks or accidents.
- Thoroughly inspect all components, paying particular attention to the condition of the steel balls, wheel edges, and bearings during disassembly and installation. Look for any signs of wear, damage, or irregularities that may require further attention.
- When installing the crane idler, carefully check and tighten each fastening screw on the wheel edge individually to ensure stability and compliance with the manufacturer’s specifications.
