Rappers are used to transmit strong shearing forces to collecting plates in order to release deposited dust particles. Rapping is the process by which electrodes and particles are broken apart by vibrations from the rappers. Often used in electrostatic precipitators, rappers relapse the caked on dust layer which then descends into a hopper. Number, size, and frequency of the rappers vary from system to system based upon the specific characteristics of the dust being collected.