Dust build up is one of the frequent problems found in the ESP that can be caused by leakage or insufficient rapping system.
The leakage might be from the casing, hopper, access door, inlet duct or nozzle which will result to sticky and hardened dust. This will not be dislodged by rapping system and can lead to short circuit inside ESP.
Worn out rapping parts or poor designed rapping system can also cause dust build up.
To prevent dust build up problem, the leakage and the rapping system condition should be prioritized and solved. In normal conditions, you can install alternative devices that will increase dust removal efficiency like sonic horn and prevent dust accumulation.