Rotor assembly is the rotating part of vertical cuttings dryer. There are scrapers between the rotor and screens basket to help for solids removing. So the scrapers are wearing parts. Manufacturer will suggest to change the whole rotor assembly with a full set scrapers. Many customer cannot understand, why the rotors are not wearing parts, but have to change together with the scrapers?
The reason is that:
The scraper is with a curved surface. Although it is a precision casting, it has machining deviation. There are mounting holes on the scrapers after casting. The rotor is also a curved surface, and the rotor itself has no standard mounting holes for scrapers.
During assembly, put the scraper on the rotor to find the best place where the curved surface of rotor and scraper can touch well, and then drill holes on rotor for fixing. After 8 scrapers are fixed to the rotor, the whole unit will be machined and do dynamically balance. Because both precision casting and assembly have deviations. Therefore, the mounting hole positions on every rotor will be not the same. And the dynamic balance can only fit the original scrapers which delivered together from the factory. That’s why the scrapers and rotor must be replaced together.
If operators want to only replace the scrapers but use the old rotors, they will need to find a workshop with vertical lathe to machine the scrapers to ensure the equal gap between scrapers and basket. and make balancing for the whole unit.
The method of using flat washers to adjust the gap between screen and rotor may solve the problem of installation. But the gap between screen and rotor maybe not equal. Do balancing will be another challenging.
It is high speed rotating equipment. If the rotor assembly is not in balance. It will cause abnormal vibration, it may damage the machine, or even cause dangerous.