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By Rick Kushinski, Service Manager
Probably one of the most overlooked preventive maintenance tasks is to change the stuffing box packing annually.
As the packing ages, it becomes hard and brittle. In this state, it loses its ability to provide an adequate seal against the outer diameter of the shaft, as well as the inner diameter of the stuffing box. This can lead to increased air leakage through the stuffing box at higher vacuum levels or excessive seal water leakage along the shaft at lower vacuum levels. The latter can also contribute to a premature bearing failure if the leak is severe enough to allow water to enter the bearing housing. When this situation occurs, we commonly find that the packing gland has been tightened to the point of creating too much friction against the shaft, which in turn causes the metalizing on the shaft to overheat and possibly crack - making the situation much worse. At this point, the pump needs to be removed for repair.
Changing the packing annually will make the task much easier to accomplish, as the packing will still be pliable. It is also very important to remove all of the packing, and replace it with new parts. Many times, when pumps come in for repair, we find that the shaft packing rings that are easily accessible, the first two or three, have been changed out but the remaining rings were left in. This will lead to the same problems mentioned earlier.
While this task is being performed, make sure that the drip tray between the stuffing box and the bearing housing is not full of debris and that the drain is clear. A clogged drain will allow water to build up in the drip tray and possibly enter the bearing housing and contribute to a premature bearing failure.