Zinc is produced by electrolysis, during which acidic vapors are generated. This harsh environment severely limits the lifetime of sensors used for positioning cathodes in the electrolyte. By using a special type of steel for the sensor housing, long sensor life is achieved.
- Extended sensor lifetime
- Reduced maintenance and replacement costs
- Excellent reliability
- Long sensing distances
- Factor 1 on steel and aluminum
- Resistant to aggressive atmospheres due to all-metal housing (1.4539 steel)
Zinc production takes place in an electrolyte bath hall comprising 106 electrolysis cells. Cathodes are lifted out of the electrolyte every 24 to 48 hours and automatically conveyed to machines that strip off the accumulated zinc deposits. After brushing and washing, the transport system returns the cathodes to the baths.
A reliable lifting and dipping process is crucial to the smooth operation of this electrolysis process. However, the process generates extremely harsh acidic vapors of sulfur and fluorine – a highly aggressive working atmosphere for both the cathode transporter and the inductive sensor monitoring its position. Originally, the customer used plastic sensors, but the vapors caused them to disintegrate. Standard V2A stainless steel sensors also became brittle after two or three months. Even the high-grade, V4A food industry sensor, which resists aggressive cleaning, became porous and started to disintegrate, presenting a risk to the electrolysis process.
Elsewhere in the plant, fittings in a special type of corrosion-resistant steel are used. This steel is suitable for chemical processes and flue gas desulfurization according to DIN 1.4539. After collaborating with the customer in trials, Contrinex produced a version of the Full Inox (series 700) sensor with all-metal housing in this 1.4539 grade. To prevent inhibition of the chemical process, a glass-fiber reinforced plastic (GRP) mounting bracket was used to mount the sensor on the transporter. Many months later, long after other sensors would have disintegrated, these special versions still function perfectly. The material retains its properties and looks the same as on day one.
The all-metal housing of the Series 700 sensor protects its sensing surface from mechanical stresses and seals it against gases and liquids. With up to three times the sensing distance of conventional proximity sensors, a safe distance from moving parts can be guaranteed, reducing the risk of collision and increasing reliability.