Why do single-girder cranes also have wheels?

What are the wheels on a single-girder crane? What types are there? What characteristics do they have? And how should they be maintained? Let’s take a closer look at the wheels on single-girder cranes together.

The core function of the wheels on a single-girder crane is to bear the crane's own weight and the load of the heavy objects being lifted. Power is transmitted to the crane's running rails via supporting equipment such as motors and reducers, which drives the wheels to rotate—thereby enabling the entire crane or the lifting trolley to move up, down, left, and right.

Types of Wheels for Single-Girder Cranes

By Application
On-rail Traveling Wheels: Typically used as the main (long-travel) and trolley (cross-travel) wheels for overhead cranes or gantry cranes. They have high usage volume and operate on specially laid rails.
Suspended Wheels: Generally serve as the running wheels for suspended single-girder cranes or electric hoists, moving along the flange plates of I-beams.
By Presence of Flanges
Double-flange Wheels: With flanges on both sides of the wheel, they are used as the main traveling wheels for overhead and gantry cranes to prevent wheel derailment. The flange height is usually 25mm-30mm.
Single-flange Wheels: Featuring a flange on only one side, they are commonly used as the trolley traveling wheels for overhead and gantry cranes. The flange height ranges from 20mm to 25mm. Due to the trolley frame’s small span and good rigidity, derailment is less likely.
Flangeless Wheels: Lacking flange barriers, these wheels are prone to derailment, limiting their application scope. For example, wheels of circular-rail cranes can be flangeless because they are constrained by a central rotating shaft. Alternatively, horizontal rollers can be added on both sides of the wheels for guidance to prevent derailment.

Materials for Single-Girder Crane Wheels
Since single-girder cranes need to withstand heavy loads, what material should be chosen for their wheels?
Typically, forging materials are represented by 42CrMo alloy steel, and the wheels of single-girder cranes are mostly forged from 45# steel. The reason for selecting this material is that it ensures the wheels have higher load-bearing capacity and better adaptability to the crane’s operation in harsh working environments.
In addition, wheels manufactured through forging processes can optimize the internal structural properties of metal components via the forging and pressing process, eliminate potential structural defects, and thus make the overall performance of the wheels superior to that of cast wheels made of the same material. However, it should be noted that even after forging and forming, the wheels still require a heat treatment process to eliminate internal residual stress and enhance the surface hardness of the wheels.

Of course, many cranes also use ductile iron as the main material for their wheels. On one hand, the special spherical structure formed inside ductile iron endows it with relatively high strength; on the other hand, cast iron itself has a relatively high carbon content, which gives it excellent wear resistance—making it particularly suitable for the working scenarios of various cranes. Additionally, the graphite in ductile iron has a certain lubricating effect, which is extremely beneficial for the smooth operation of the wheels on the crane. Therefore, when manufacturing wheels for single-girder cranes, the top priority is to ensure the wheels have sufficient contact strength and wear resistance. If these two core requirements cannot be met, it is necessary to carefully consider alternative materials.

Characteristics of Wheels for Single-Girder Cranes
High Strength: Manufactured via forging processes, they can withstand the crane’s weight and the pressure generated during operation. They also offer excellent wear resistance, extending service life.
Lightweight Design: Constructed from high-strength low-alloy steel, reducing wheel weight and the crane’s overall load. This improves operational efficiency and may lower energy consumption.
Superior Mechanical Properties: Forging optimizes the metal’s microstructure, endowing the wheels with excellent strength and toughness to operate stably under loaded conditions.
Smooth Operation: High precision in design and manufacturing ensures the crane runs stably, minimizing vibration and noise during operation.
Environmental Adaptability: Capable of adapting to various working conditions such as temperature changes and humidity, meeting the requirements of different work scenarios.
Heat Dissipation Performance: The design facilitates heat dissipation, preventing heat accumulation from prolonged operation that could affect wheel performance.
Corrosion Resistance: Special treatments or corrosion-resistant materials enhance the wheels’ ability to resist corrosion in harsh environments.

Maintenance of Single-Girder Crane Wheels
Maintenance of single-girder crane wheels is a critical step to ensure the crane operates safely and smoothly, as well as to extend the equipment’s service life. Improper wheel maintenance can lead to severe issues such as rail wear, abnormal operating noise, rail gnawing, and even wheel derailment.
1. Daily Inspection
Check if the wheel treads and flanges have signs of wear, cracks, deformation, or rail-gnawing marks.
Verify that the wheel makes uniform contact with the rail, with no uneven loading or jamming.
Inspect the wheel axles and bearing components for abnormal noise or overheating.

2. Regular Lubrication
For rotating components such as wheel bearings and journal necks, apply suitable grease.
Before lubrication, it is necessary to clean away oil stains and iron filings to ensure the lubrication channels are unobstructed, preventing impurities from mixing in and exacerbating wear.
For cranes used in heavy-load or high-frequency operations, the lubrication interval should be shortened to once every 15 days.

3. Regular In-Depth Inspection
Measure the wear of the wheel treads. When the wear exceeds 10% of the original thickness, or obvious pits or spalling occur, the wheels need to be replaced.
Check the thickness of the wheel flanges. If the wear exceeds 20% of the original thickness, or if the flanges are deformed or cracked, they should be replaced promptly.
Tighten the wheel axle end nuts and connecting bolts to prevent wheel deviation or detachment caused by loosening.
Verify the wheel installation accuracy to ensure the wheel axis is parallel to the rail, avoiding the persistent occurrence of rail gnawing.

Now that we have understood what the wheels of a single-girder crane are, their types, and daily maintenance methods, we will be able to operate and use the crane more effectively and safely in the future, while also extending its service life.