Drive magnet for the wiper system on Hanovia medium-pressure ultraviolet disinfection systems. The wiper is driven through the chamber wall magnetically, so there is no shaft penetration to seal against system pressure — the magnet is what transmits the drive. The quartz sleeve is the only optical path between the lamp and the water, so any film of scale or iron on its outer surface cuts the delivered UV dose. The wiper sweeps the sleeve on a timed cycle to keep transmission at the design figure. A weak or cracked magnet shows itself as a wiper that stalls partway along the sleeve or fails to reach its limit switch. Reference number 2267-0409.