Right Lubricant for the Right Job Helps Lower Machine Operating Costs, The

Pulp & Paper, Jul 2004 by McFann, Mark

Bearing temperatures and vibration readings were monitored on the two paper machines before and after switching to highperformance synthetic grease. Equipment temperatures were taken four weeks after lubrication with the original synthetic grease and then four weeks after lubrication with the high-performance synthetic grease. Changing to the high-performance synthetic grease dropped temperatures an average of 3O0F (Figures 1 and 2). The lower temperatures have been stable for 19 months.

Vibration levels prior to the lubricant upgrade were normal but since the change, many vibration frequencies have dropped. No bearing vibration reading on either machine increased.

Most importantly, neither paper machine experienced a single unscheduled or scheduled bearing replacement since upgrading lubricants during the first two years of service. The annual production loss in dollars from bearing failures during two years of using the original grease was $64,625 (5 failures x 5.5 hours per failure x $4,700 per hour lost time/2 years).

In addition to eliminating the downtime expense due to the failed bearings, upgrading lubricants enabled the mill to reduce maintenance expenses by reducing the frequency of lubrication intervals. The plant was originally using forty 120-lb kegs of synthetic grease annually for two machines at a cost of $500/keg. The annual cost was $20,000.

The high-performance synthetic grease allowed the mill to extend lubrication intervals from four weeks to twelve weeks. Although the high-performance synthetic grease had a higher purchase price at $632/keg, only sixteen 120-lb kegs were needed annually, for a total cost of $10,112. The combined annual financial impact of reduce maintenance cost and lubrications purchases was significant.

* Annual savings by eliminating bearing failures: $64,625

* Annual savings reducing the amount of lubricant purchased: $9,888

* Total annual savings: $74,513.

Case Study: Press Section Savings

Paper mill reliability staff determined that the first press suction roll drive side bearing was stage failing. This was determined by a temperature rise from the normal 165° to 1750F to a temperature of 265°F and excessive vibrations.

Reliability staff decided to attempt to prolong the life of the equipment without making immediate repairs. Instead, they elected to simply upgrade lubricants. Although they were already using a major brand synthetic grease, they believed they would be better served by trying a synthetic grease from a manufacturer who specializes in high-performance lubricants.

Upon making the change, the bearing temperature went from 265°F to 160°F in less than one hour, and the vibrations decreased. The mill continued to run until its next scheduled downtime and changed the bearing even though all indications were that the bearing was no longer problematic. Reliability staff concluded that the upgraded grease prevented an approximate 12-hour downtime, which saved the mill in excess of $36,000 in downtime expense.