The "Rotary Joint" of Excavators! A Complete Guide to Slewing Ring (Large Turntable): Structure, Selection & Maintenance

I. Understanding the Slewing Ring (Large Turntable): The "Rotary Core" of the Excavator

1. Structure: 3 Key Components Support "Rotation + Load - Bearing"

• Inner Ring & Outer Ring: Circular rings made of high - strength alloy steel. The inner ring is connected to the upper machine body (cab, boom), while the outer ring is attached to the chassis. The inner side is equipped with a "raceway" for placing rolling elements;

• Rolling Elements: Steel balls or rollers (about 50 - 80 pieces for a 20 - ton excavator). Their surfaces are quenched (hardness HRC55 - 60) to reduce friction;

• Cage & Seals: The cage separates the rolling elements to prevent friction between them. The seals (rubber sealing rings) prevent impurities and water from entering and retain lubricating grease.

2. Core Principle: "Rolling Friction" Enables Flexible Rotation

The swing motor drives a small gear, which meshes with the inner or outer ring of the slewing ring. The rolling elements in the raceway roll, allowing the upper machine body to rotate 360 degrees. At the same time, it transfers the weight of the upper body to the chassis, realizing the dual functions of "rotation + load - bearing". It can be compared to an "office chair swivel base".

3. Importance: Without It, the Excavator "Can’t Turn Around"

• Foundation for Rotation: Without the slewing ring, the bucket can only operate in one direction, reducing work efficiency by 60%;

• Key to Load - Bearing: It bears the weight of the upper body (10 - 12 tons). If damaged, the machine body may tilt;

• Expensive Maintenance: An imported slewing ring costs USD 2,750 - USD 6,875. Replacing it requires hoisting the machine body, resulting in 3 - 5 days of downtime, and the downtime loss is even higher than the maintenance cost.

II. 5 Things the Slewing Ring Fears the Most!

1. Lack of Lubricating Grease: Dry friction occurs between the raceway and rolling elements, causing scratches and abnormal noises. The repair or replacement cost ranges from USD 137.5 - USD 6,875;

2. Impurities & Water Ingress: Cracked seals allow gravel and water to enter the raceway, leading to wear and rust and accelerating damage;

3. Unilateral Load - Bearing: Long - term one - sided operation causes "uneven wear" of the raceway, reducing its service life by half;

4. Sudden Acceleration / Emergency Stop: Impact loads cause rolling elements to break and raceways to deform, resulting in machine body jamming;

5. Overload Operation: Installing overweight equipment or digging excessive materials exceeds the load - bearing limit, leading to raceway cracking.

III. Cost - Effectiveness Comparison of Slewing Rings from Domestic and Foreign Excavator Brands

IV. 5 - Step Maintenance for the Slewing Ring

1. Add Grease on Time: Under heavy working conditions (e.g., mines), add "lithium - based grease" every 100 - 200 hours; under light working conditions (e.g., municipal engineering), add it every 300 - 500 hours until the grease overflows;

2. Inspect Seals: Check weekly if the seals are cracked, and after rain, check for water leakage. Replace damaged seals promptly (domestic seals cost USD 27.5 - USD 68.75 per set);

3. Avoid Unbalanced Loads & Overloads: Alternate operations on both sides of the machine, do not install overweight equipment, and do not dig excessive materials;

4. Operate Smoothly: Push and release the swing control lever slowly, avoiding sudden acceleration and emergency stops;

5. Protection During Idleness: If the excavator is idle for more than 1 month, rotate the slewing ring 360 degrees and replenish grease monthly. Cover it with a waterproof cloth when parked outdoors.

V. Summary

   The slewing ring is the "rotary joint" of the excavator. There are 3 key points to remember: understand its structure (inner ring/outer ring + rolling elements), avoid 5 types of risks (lack of grease, impurity ingress, etc.), and conduct maintenance in 5 steps. Proper maintenance of the slewing ring ensures smooth rotation of the excavator, fewer failures, reduced maintenance costs, and improved efficiency — truly "saving big money with small maintenance"!

About SPARKLING MACHINERY:

   - Founded in 2013, SPARKLING focuses on high-quality excavator parts across hydraulics, undercarriage, engines and electrical systems. We prioritize stability, precision and continuous service, offering worldwide distribution, tailored solutions and strict QC to help customers reduce cost and increase uptime.

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