Discharge Electrode Rapper Shaft Insulators

As dust accumulates on the discharge electrodes of an electrostatic precipitator, the clearance between the discharge electrodes and the grounded collecting electrodes will diminish. Rappers are used to clean of the discharge electrodes to maintain clearances.

The rapping energy is transmitted to the discharge electrodes through vertical multi-sectioned shafts (i.e., high voltage rapper shafts are comprised of a minimum of two sections. In two-piece shafts, the upper-most section is the rapper shaft insulator; in three-piece shafts, the center section is the insulator). The insulator shaft section penetrates to the precipitator exterior and isolates the high voltage system for protection of personnel around or on the precipitator as well as for the protection of the rapper itself. Discharge electrode rapper shaft insulators must provide superior electrical isolation at the casing penetrations as well as possess superior mechanical characteristics for the reliable transmission of rapping energy to the discharge electrodes.

Rapper shaft insulators, and their connections, are selected with consideration given to the process and operating environment, equipment clearances and type of rapper. Currently, Hamon Research-Cottrell provides discharge electrode rapper shaft insulators constructed of porcelain, alumina and fiberglass reinforced plastics. Shafts are available in a variety of lengths with shaft connections dependent upon the type of insulator shaft material, design requirements and/or customer preference. Hamon Research-Cottrell predominantly uses an industry standard 3 1/2° tapered connection for new and retrofit installations.