However, the source of some troubles may be different because of construction differences. Positive-displacement blowers have a set of gears to drive and synchronize the rotation of the rotors. Many of these blowers are driven by a serrated shaft. Regardless of construction differences, the basic problem in both types of blowers is in maintaining the necessary small clearances. If these clearances are not maintained, the rotors and the case will be damaged and the blower will fail to perform its function.
Worn gears are one source of trouble in positive-displacement blowers.
A certain amount of gear wear is expected, but damage caused by excessively worn gears indicates improper maintenance procedures. You can use this record to establish the rate of increase in wear, to estimate the life of the gears, and to determine when it will be necessary to replace the gears. Scored rotor lobes and casing may cause blower failure. Scoring of blower parts may be caused by worn gears, improper timing, bearing failure, improper end clearance, or by foreign matter. Any of these troubles may be serious enough to cause the rotors to contact and damage the blower extensively.