In modern industrial equipment, slewing bearings are core components for achieving rotary motion, widely used in cranes, wind turbines, steel structure rotary tables, and tunnel boring machines. They can withstand not only large radial loads but also axial forces and overturning moments, directly affecting the safety and efficiency of the equipment. This article will systematically analyze the classification and selection points of slewing bearings to assist in engineering practice.

Main Classifications of Slewing Bearings

Slewing bearings can be classified according to the type of rolling elements, structural form, and installation method. Different types of bearings are suitable for different engineering needs and load conditions.

1. Classification by Rolling Element Type

Spherical Slewing Bearings: Use steel balls as rolling elements, resulting in low frictional resistance and flexible operation, suitable for light to medium load scenarios.

Typical Applications: Industrial robots, light lifting machinery, etc.

Roller Slewing Bearings: Use cylindrical rollers, tapered rollers, or crossed rollers, offering high load-bearing capacity, particularly suitable for bearing radial forces and overturning moments.

Typical Applications: Tower cranes, tunnel boring machines, steel structure rotary tables.

2. Classification by Structural Form

Single-row slewing bearings: Compact structure, moderate load-bearing capacity, suitable for small and medium-sized machinery.

Double-row slewing bearings: Rolling elements are arranged in two rows, increasing load-bearing capacity, suitable for medium and large-sized machinery.

Four-point contact slewing bearings: A single row of steel balls can withstand both positive and negative axial loads and radial forces, widely used in engineering machinery.

3. Classification by Installation Method

Internal gear slewing bearings: Gear ring is on the inner ring, commonly used in turntables, rotary worktables, etc.

External gear slewing bearings: Gear ring is on the outer ring, suitable for gear-driven equipment.

Gearless slewing bearings: Rotation is achieved through hydraulic or direct drive, mostly used in high-precision machinery.

Slewing Bearing Selection Guide

Choosing the right slewing bearing not only ensures stable equipment operation but also reduces maintenance costs and extends service life. The following factors should be considered when selecting slewing bearings:

Load Type and Size

Small, light-load equipment can use ball bearings.

Medium-to-large equipment with high load-bearing requirements should use roller bearings or crossed roller bearings.

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For more detailed information on slewing bearing classifications, please click to visit: https://www.mcslewingbearings.com/a/news/slewing-bearing-classification.html

Slewing bearings are core rotating components in construction machinery, lifting equipment, wind turbine generators, and large machine tools, and their performance directly affects equipment safety and production efficiency. However, tooth breakage is a frequent problem after long-term use, leading not only to equipment downtime but also potentially high maintenance costs. So, why do slewing bearings break teeth? And how can this be prevented scientifically? This article will provide a systematic analysis.

Main Causes of Slewing Bearing Tooth Breakage

1. Overload Operation

Slewing bearings are designed with a rated load range. Overloading causes stress concentration on the tooth surface, accelerating material fatigue and ultimately leading to tooth breakage. This is especially true in cranes or large excavators, where improper operation poses a very high risk of overloading.

2. Improper Lubrication

Insufficient lubrication or low-quality lubricating oil leads to direct metal-to-metal contact between the tooth surfaces, increased friction, localized temperature increases, and rapid gear wear. Neglecting lubrication maintenance over a long period is a major cause of tooth breakage.

3. Installation and Adjustment Issues

The installation accuracy of the slewing bearing directly affects the gear meshing state. Uneven installation or preload can lead to uneven gear stress and excessive localized stress, easily causing tooth surface damage or even tooth breakage.

4. Material and Heat Treatment Defects

Inadequate strength, hardness, and surface treatment of gear steel can easily cause micro-cracks under high stress environments, eventually leading to tooth breakage due to long-term accumulation. Uneven carburizing or insufficient quenching are also common hidden dangers.

5. Harsh Operating Environment

High temperatures, dust, and corrosive media can accelerate tooth surface wear or corrosion, reduce load-bearing capacity, and increase the risk of tooth breakage.

Scientific Prevention Measures for Slewing Bearing Tooth Breakage

1. Strict Load Control

Ensure equipment operates within its design load range and avoid frequent overloading. For high-load machinery, slewing bearings with higher rated loads can be selected to increase safety margins.

2. Optimize Lubrication Scheme

Use lubricating grease that meets specifications and regularly check the oil level and quality to ensure adequate lubrication of the tooth surface. For heavy-duty or high-speed operating equipment, consider a circulating lubrication system to improve tooth surface protection.

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For more detailed information on the causes and prevention of slewing bearing tooth fracture, please click to visit: https://www.mcslewingbearings.com/a/news/causes-and-preventive-measures-for-broken-teeth-in-slewing-bearings.html

Tunnel construction is one of the most technically demanding tasks in modern infrastructure engineering. From complex geological conditions to strict safety standards and long-term durability requirements, every design decision has a lasting impact on project success.

Among these decisions, selecting the right tunnel lining system is critical. An unsuitable lining solution can lead to structural risks, water leakage, excessive maintenance costs, or even premature failure of the tunnel.

In this guide, we break down the most common types of tunnel lining systems, compare their advantages and limitations, and help you determine which tunnel lining solution best fits your project conditions.

Overview of Common Tunnel Lining Systems

1. Initial (Primary) Tunnel Support

Initial support—also referred to as primary or temporary lining—is installed immediately after tunnel excavation. Its primary role is to stabilize the surrounding ground and prevent deformation or collapse during construction.

Typical materials include shotcrete, steel ribs, rock bolts, or timber frames, selected according to ground conditions.

Key advantages:

Provides immediate structural stabilization after excavation

Reduces construction-stage safety risks

Flexible application in varying geological conditions

Limitations:

Not designed for long-term structural performance

Usually requires a secondary lining for durability

Best suited for:

Soft soil, weak rock formations, and tunnels with high deformation risk.

2. Secondary (Permanent) Tunnel Lining

Secondary lining is the final structural layer designed to ensure the tunnel’s long-term strength, durability, and waterproofing performance. It is typically constructed using reinforced concrete, cast-in-place concrete, or fiber-reinforced sprayed concrete.

Key advantages:

High load-bearing capacity and long service life

Excellent water tightness and structural integrity

Customizable geometry for complex tunnel designs

Limitations:

Longer construction time compared to temporary supports

Higher labor and material costs

Best suited for:

Urban tunnels, deep underground tunnels, and projects requiring high durability and waterproofing.

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For more detailed information on tunnel lining system types, please click to visit: https://www.gf-bridge-tunnel.com/a/blog/types-of-tunnel-lining-systems.html

Tunnel construction is a highly specialized field where safety, durability, and long-term performance are non-negotiable. While primary supports stabilize the initial excavation, the secondary lining acts as the tunnel’s ultimate protective layer, ensuring reliability for decades. Understanding its importance helps engineers, contractors, and infrastructure planners maximize tunnel lifespan while reducing maintenance costs.

What is Tunnel Secondary Lining?

Tunnel secondary lining is the final structural layer applied after excavation and primary supports (like shotcrete or temporary linings). Unlike the primary lining, which mainly provides temporary stability, secondary lining ensures long-term protection and performance. Key functions include:

Structural Support: Reinforces the tunnel shell against soil movement and seismic activity.

Waterproofing: Prevents leaks that could compromise safety and equipment.

Environmental Resistance: Protects against chemical erosion, abrasion, and temperature fluctuations.

In essence, secondary lining serves as the tunnel’s long-term armor.

How Secondary Lining Impacts Tunnel Lifespan

A well-designed secondary lining can extend tunnel life by decades, while poor-quality linings lead to early deterioration. Its benefits include:

Structural Safety

Secondary lining strengthens the tunnel shell, reducing the risk of cracks, deformation, or collapse caused by soil shifts or seismic activity.

Leak Prevention

Water infiltration is a common tunnel problem. Secondary lining combined with waterproof membranes blocks water seepage, protecting electrical systems and reinforcing steel from corrosion.

Durability Against Environmental Stress

High-quality lining materials resist abrasion, chemical exposure, and temperature changes, maintaining performance over time.

Common Risks When Secondary Lining is Neglected

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For more detailed information on tunnel secondary lining, please click to visit: https://www.gf-bridge-tunnel.com/a/blog/what-is-tunnel-secondary-lining.html

Jaw crushers are widely used in mining, building materials processing, and metallurgical industries. Their output directly determines the efficiency and cost control of the entire production line. However, in actual operation, many users find that even with correct equipment selection, the actual output is far lower than the design value.

The insufficient output of jaw crushers is often not caused by a single fault, but by a combination of factors such as feeding, parameter settings, wear conditions, and operating methods. This article will analyze the key factors affecting jaw crusher output based on field practice and provide actionable optimization suggestions to help you quickly improve crushing efficiency.

Causes and Solutions for Insufficient Output of Jaw Crushers

1. Feed particle size is too large or uneven

Feed size exceeding the design range, or excessive particle size fluctuations, will lead to unstable crushing chamber load, affecting the effective crushing time of the jaw plates, and ultimately reducing overall output.

Optimization suggestions:

Control the feed particle size to not exceed the maximum allowable feed size of the equipment.

Improve feed uniformity through screening or pre-crushing equipment.

2. Improper Discharge Opening Size Adjustment

The discharge opening directly determines the product particle size and processing capacity:

Discharge opening too large: Short material residence time, insufficient crushing.

Discharge opening too small: Prone to material blockage, machine stalling, and frequent shutdowns.

Optimization Recommendation: Regularly calibrate the discharge opening parameters according to material hardness, moisture content, and target output to avoid “one-time setting without long-term adjustment.”

3. Severe Wear of Jaw Plates, Bearings, and Other Components

Jaw plate wear reduces biting force, while abnormal bearings increase operating resistance; both significantly affect the effective capacity of the jaw crusher.

Optimization Recommendation:

Regularly check the jaw plate tooth profile and thickness.

Check the bearing condition promptly if abnormal vibration or temperature rise occurs.

Use highly wear-resistant materials to improve continuous operation capability.

4. Decreased Efficiency of Motor and Transmission System

Common problems include:

Unstable motor speed

Belt slippage or aging

Poor gear meshing

These problems directly cause power loss, making the equipment appear to be running, but actually inefficient.

Optimization suggestions:

Regularly adjust belt tension

Check motor load and power matching

Ensure proper lubrication of the transmission system

5. Non-standard operation leads to efficiency loss

Improper operating habits can also silently reduce output, for example:

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For more detailed information on what to do if your jaw crusher’s output is insufficient, please click to visit: https://www.yd-crusher.com/a/news/jaw-crusher-output-insufficient.html