Bearings Cut Downtime at Major Phosphate Plant

Bearings on a chain mill application at a major phosphate plant are still in operation more than eight months after installation, while the bearings they replaced often failed in as little as three or four days. The resulting reduction in downtime and added service life has resulted in significant cost savings for the company.

At the facility, the company processes phosphate for use in animal nutrition. Raw material that has been partially crushed and cleaned after mining is pulverized in chain mills. In the mills, chains inside spinning drums break the material down into small particles that can be processed for use in animal feed products. Shock loading on the bearings supporting the three 15- or 16-in. shafts on which the drums turn can be severe, and the SAF-type bearings used in this application were failing after as little as three or four days of service.

Bearings Meet the Severe Service Challenge

To extend the service life of the bearings, the company replaced the existing split-block SAF-type bearings with Rexnord ZAF6000 Series SHU–RLOK adapter mount roller bearings.

A company spokesman explains, “The previous bearings literally started failing a few days after they were installed, so the user was faced with both the replacement cost and the downtime. Instead of replacing the bearings with an exact interchange [that was] likely to fail, we selected the higher-capacity Rexnord bearings that could be installed with minor mounting modifications.”

In addition, the bearing design provides better sealing to protect against possible contamination, including corrosive and abrasive damage from long-term exposure to the phosphate material.

The ZAF6000 bearings are solid-housed, shaft-ready units for installation. They are greased and the clearance is preset, so they can be taken out of the box and mounted to the shaft. They feature a positive locking system that maintains mounting tightness during operation. The tapered adapter sleeve provides greater shaft grip and eliminates the shaft damage caused by loose bearings. In addition, the SHU–RLOK technology makes it easier to remove the bearings from the shaft without causing damage, saving both time and repair costs. The new bearings also incorporate Spyglass Optical Strain Sensing (OSS) technology, which provides instant feedback to achieve optimal shaft grip. It eliminates damage to the shaft and bearing that can be caused by improper tightening during bearing installation.

The first Rexnord bearings were installed in April 2007 and continue to operate reliably to date. The company anticipates significant cost savings from the reduced downtime and repair costs that the new bearings are expected to deliver. A Guaranteed Cost Saving Analysis by Rexnord estimates that the company will save more than $39,000 annually. As bearings on additional mills fail, the company plans to replace them with the new bearing design.

For more information, contact Rexnord at 866-739-6673 or www.rexnord.com