Why are three-row roller slewing rings so expensive, and where are they used?

Structure:​ It consists of an upper and lower row of axial rollers to withstand overturning moments, and a middle row of radial rollers to handle radial loads. This clear division of labor allows its load-bearing capacity to far exceed​ that of single-row ball or cross roller slewing rings of the same size.

Applications:​ They are used in ultra-heavy-duty and extreme working conditions. Examples include the main/auxiliary boom slewing of crawler cranes over 1600 tons, large port cranes, offshore platform cranes, tunnel boring machines (TBMs), and giant radar antenna pedestals.

Reasons for High Cost:

• Complex Structure & Extreme Manufacturing Difficulty:​ The precision machining and assembly of three independent, perfectly aligned roller raceways is vastly more complex.

• Stringent Material Requirements:​ The components demand ultra-high purity, high-strength, and toughness-grade alloy steel with specialized heat treatment.

• Requires Specialized Equipment:​ Manufacturing often involves massive, custom-designed CNC machines for machining the giant components.

• Low Production Volume & High Expertise:​ They are made-to-order for mega-projects, lacking economies of scale, and require exceptional engineering and skilled labor.