In intake basins at treatment plants, sensors for monitoring temperature and fill level are mounted onto the bridges of continuously rotating rakes. The signals are transmitted constantly via sliding contacts, and each signal requires two sliding contacts.
The sliding contacts get worn down by the continuous movement of the bridge and exposure to weather effects, and must be replaced periodically. The goal is to completely remove all sliding contacts from this application. Hazardous-location requirements must also be met, as this section of the plant is located in a Zone 2 explosion-hazardous area.
Battery-operated WirelessHART adapters, which wirelessly transmit data from fill level and temperature sensors to the control system, replace the sliding contacts—no matter if these are 4 mA ... 20 mA or HART field devices. In new plants, a WirelessHART temperature converter can be used to measure and transmit temperature measurements.
Since the adapters can be fitted at a distance of up to 250 m, it is possible to equip other sections of the plant, such as the digestion tank, with WirelessHART adapters or temperature converters.
To dispense with sliding contacts and implement wireless solutions offers many advantages: Wear and weathering no longer cause the removal of expensive sliding contacts. This helps to avoid measurement downtimes. The battery, which can last up to seven (WHA-ADP) or ten (WHA-UT) years in this application, can be replaced in just one minute.