The Significance and Applications of Slew Bearings

Slew bearings, at their core, are large-diameter bearings designed to handle heavy axial, radial, and moment loads while enabling smooth and controlled rotation.

Slew bearings, also known as slewing rings or turntable bearings, are large-diameter bearings designed to handle heavy axial, radial, and moment loads while enabling smooth and controlled rotation. They are used in a variety of heavy-duty applications, including electric arc furnaces, ladle turrets, and caster turrets. Slew bearings must be able to withstand extreme temperatures, heavy loads, and low speeds. They must also be highly reliable, as unscheduled downtime can cost thousands of dollars per hour.

The life of slew bearings is a challenging one. They must sit for long periods of time, waiting for their chance to spring into action. When that time comes, the bearings must pivot on an axis and rotate a heavy load very slowly, 90 or 180 degrees. Once they have completed this task, they wait a long while, 30 or 45 minutes typically, before being called upon once again. Slewing bearings do a lot of sitting around, yet they must respond every time, and they must do it reliably for years on end. So they have to be well-made.

Timing is everything in metalmaking, and if the parts do not run in order with precision, messes get made. They are big, hot, expensive messes, so the parts need to be reliable. In an electric arc furnace, temperatures can reach 2,500 degrees Fahrenheit and slew bearings are counted upon to rotate thousands of tons of molten steel. NSK slew bearings come optimized for the application, maintaining stability and precision under high temperatures, heavy loads, and low speeds. Lubrication features – designed to accommodate customers’ systems – facilitate grease replenishment to reduce friction and wear with a clean supply of lubricant. Seal and shield options promote long-life reliability, an essential prerequisite in these applications. That is of vital importance because any unscheduled downtime can cost thousands of dollars an hour in lost work.

Design features

High-capacity, triple-row roller bearing design (typical)

With segmented steel cage (additional options available)

With internal, external, or no integrated gearing

Various standard or custom seal/shield options

Lubrication features to customer specification

Outer diameter range of 1 to 6 meters

Ball bearing and combined ball/roller bearing slewing rings are also available

Maintaining slew bearings

While inventory management to avoid untimely shortage of such important bearings is standard practice, proper handling goes well beyond simply keeping them in stock. Improperly stored slewing rings can be impacted with corrosion damage, challenging their suitability for operation and presenting the prospect of extended downtime for costly bearing reconditioning.

Proper maintenance of bearings is essential to ensure long life and reliability. This includes disassembly and tank storage of all components, ongoing condition monitoring with visual inspection and oil sampling, assembly and installation, and anticipation of end of life and timely replacement.

Proper maintenance of bearings can save mills hundreds of thousands of dollars from reduced downtime. It can also improve productivity and efficiency and reduce the number of times the bearings need maintenance over their life span.

Overall, slew bearings are critical components in heavy-duty applications, and their proper design, installation, and maintenance are essential to ensure reliable operation and extended service life.