Checking Grease Quality in Corrugating, Pressure and Preheater Roll Bearings

Within the corrugating industry, the single-facer machine is considered the “heart” of the corrugating production line. If a corrugating or pressure roll bearing fails unexpectedly during production, downtime is inevitable as changing out the bearing means changing out the affected roll. And very often, the roll change is a multi-hour, if not multi-day, job.

Because unexpected downtime due to a bearing failure is so costly and disruptive, knowing the condition of the unseen grease inside the bearing is critical. And because the grease cannot be visually inspected while inside the bearing, Maintenance Managers and their lubrication technicians must depend on other means of verifying the state of the working grease.

For every single-facer machine, there is a specified interval stated in the owner’s manual. Often times, this interval is measured in time, such as every three months. Other times, the interval is measured in linear feet of board produced, such as every 10 million feet. But for the most part, the personnel charged with insuring the condition of the grease depend on a visual inspection.

The visual inspection of grease inside the bearing is most often accomplished by pumping in new, white grease into the bearing until grease exits the bearing from a port or opening, most commonly, a bearing seal. This exiting grease is inspected and subjected to a kind of color test. The color test consists of a range of shades, from white to black. In short: white equals good, black equals bad and the range of colors between these two color extremes indicate the various stages of internal bearing wear. Here is an example of a grease color test:

The visual color test is commonly used to determine the condition of the grease over inspection in a specified time or linear interval by corrugator personnel. In short, new grease is pumped in until white grease begins to exit the bearing. This method attempts to insure that most of the grease inside the bearing is intact, in terms of performance capability, and little or no completely depleted grease is inside the bearing.

So, with regards to the corrugating industry, you could say that “Seeing is believing”. Nye's NyeCorr® 140 is a synthetic bearing grease formulated specifically for the maintenance of single-facer and pre-heater bearings in the corrugating industry.

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