When lubricating an unsealed pillow block bearing, when should the user stop pumping the grease gun?

When lubricating an unsealed pillow block bearing, the correct approach involves continuing to pump the grease gun until the old grease begins to flow out of the bearing. This method ensures that the bearing is effectively cleaned out and filled with fresh grease, promoting optimal lubrication and performance.

Pumping until old grease exits indicates that the old lubricant is being expelled, which is crucial because it could contain contaminants or have broken down over time. This practice helps to maintain the integrity of the bearing and prevents potential failures that could arise from insufficient or degraded lubrication. By ensuring that only new grease is present, the bearing will operate more smoothly, reducing friction and wear.

The other approaches, such as stopping when pressure increases or after a fixed number of pumps, do not guarantee that old grease is being fully purged from the bearing. Likewise, stopping as soon as new grease is added could lead to incomplete lubrication, reducing the effectiveness of the maintenance performed on the bearing. Therefore, the practice of ensuring that old grease flows out is essential for proper lubrication and the longevity of the bearing.