Using Air-Oil Lubrication for Slab Casters

Dave Stoyanoff, DropsA USA

Grease systems have long been popular in lubricating bearings located in the spray chamber of a caster. However, the harsh and steamy environment leads to an influx of water into the bearing between grease lube cycles and eventually destroys it.

Air-oil not only lubricates but also pressurizes the bearing cavity, preventing water and dirt ingress from happening.                     

Installation of air-oil systems at several U.S. steel mills has resulted in a substantial increase in bearing life. All mills have reported an improvement in their number of slab heats. One steel mill in particular has experienced an increase from 1,200 heats with grease to more than 9,000 using air-oil over the past eight-plus years.    

A typical air-oil system consists of the following:

  • Oil-pump supply package using gear, vane or pneumatic drum pump arrangement with appropriate valves and diagnostic feedbacks like oil level, temperature, etc.
  • Air-oil dual-line distributors     
  • Control package to operate and monitor system
  • Clean and dry plant air supply with pressure monitoring

 Reduced bearing costs are just one of the advantages of the air-oil system. Other positives include:

  • Large reduction in lubricant consumption and cost
  • Longer segment life than with grease
  • Greater and improved housekeeping as segments are cleaner
  • Reduced environmental impact, as excess oil can be removed and disposed of easier from coolant tanks than grease
  • Bearings run significantly cooler
  • Segment clean-up time is greatly reduced
  • Bearing inspection time is quicker
  • Cost savings in drive motor energy usage 

Typically, a system includes a pump to automatically feed a number of dual-line air-oil distributors mounted on each segment feeding the roll bearings. An oil-pressure switch provides monitoring of both oil lines, while an air-pressure switch monitors the air-supply pressure. System operation and diagnostic feedback are handled by a dedicated controller or in the programmable logic controller (PLC) brains servicing the caster pulpit.

Dave Stoyanoff is the general manager of DropsA USA Inc., with more than 35 years of experience in hydraulic and lubrication systems. He is based out of Sterling Heights, Mich. For more information, visit the DropsA website at or contact Dave via e-mail at or by phone at 586-566-1540.

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