subject: Something about over- lubrication of Bearings [print this page] As to the different kinds of machineries, lubrication is very necessary for them. It is no doubt that the proper lubrication can make the service life of these machineries longer, whereas the improper lubrication may cause damage to them.
In our daily life, many maintenance managers may lubricate machines referring to instructions in the factory manual that comes with new equipment. Lubricating by the book (preventive lubrication) may be the way which has been done since the beginning of the industrial revolution. Today, time-based lubrication frequency alone may no longer be valid. In fact, it could be harmful to the health of bearings and other vital machine parts.
Not all bearings need to be lubricated on a predetermined schedule. If they do, they might not need as much lubricant as the manual recommends. This could result in over-lubrication, a condition that outranks lubrication starvation as one of the most common causes of bearing failure.
Due to the above mentioned reason, it is very necessary to do the proper lubrication to bearing products. And many companies have taken measures to achieve this goal. Most of them start to follow a condition based approach to lubrication. This strategy utilizes ultrasound monitoring equipment to determine precisely which bearings need lubrication and when they need.
Using ultrasonic detectors, a program can be established that reveals these conditions, while enabling the technician to know how much lubricant to apply. The condition of the bearing determines the frequency and amount of lubricant, and whether lubrication at any given inspection interval is really necessary at all. It can distinguish the high frequency sound waves easily.
Over-lubrication may be addressed by ultrasound inspection. When too much lubricant is put into a bearing housing, pressure builds up and can lead to a viscous shear condition. This makes it harder for the rolling elements to move, causing the rolling elements to begin to produce heat and go out of tolerance.
How to prevent from the over-lubrication? Knowing when and when not to lubricate can prevent over-lubrication. This is achieved by setting a baseline, and monitoring the equipment on a set schedule to determine if lubricant is needed, and if so, exactly how much. A baseline for a bearing reflects in decibels the level at which it is operating under normal conditions with no discernable defects due to improper lubrication.
Another method is that you can monitor the bearing ultrasonically as lubricant is being applied. Lubricant should be added slowly, allowing sufficient time to uniformly cover the bearing's surface, until the baseline dB is reached.
