ELECTRICAL EQUIPMENT, CABINETS, AND FIELD BOXES
Electrical and control installations should be limited to those that are necessary for the safe and correct operation of the process equipment. However, a significant part of both the electrical and control installations is still located within the process area, e.g., cabling to power motors of plant machinery, control cables connecting sensors via field boxes/cabinets to the plant control system, etc. But, little by little, wireless transfer of data between instruments and control equipment and battery-supplied low-energy sensors and actuators are finding their way in the industry.
Electrical equipment should have an IP55 rating at a minimum. Preference is given to dust- and moisture-tight electrical equipment that can be hosed down with powerful water jets (IP66) or even better (IP67 & IP67K). IP69K rating, to German standard DIN 40050-9, is required for high-pressure, high- temperature, wash-down applications. Electrical equipment must be protected from things falling or product spilling on it. During cleaning, covering of electrical equipment with polyethylene or equivalent film is recommended.
Electrical equipment usually produces heat, and therefore must be in the possession of a dedicated cooling device. Fans ventilate (blow) heat out of the equipment in the environment by drawing in cooler outside air, circulating it throughout the case and expelling it to the outside. But along with the cooler air comes dust, microorganisms and eventually moisture, which easily accumulate in dry electrical equipment (Fig. 6.61). To avoid heat, dust and microorganisms being blown on the food during processing, the electrical equipment should be positioned away from the product zone. A more recommended alternative to ventilators is the use of the self-cooling capabilities of a casing by means of creating an internal air circulation and achieving temperature reduction through the casing surface. If this does not provide sufficient cooling, then additional cooling could be provided by fixing an air-to-water type heat exchanger to the casing (Moerman, 2011).
Direct or indirect incidental contact between the electrical installation and food cannot always be fully excluded and may possibly result in contamination of the food product. In all cases where product contact cannot be fully excluded, electrical installations have to be used that are suitable for these sensitive areas. Electronic devices positioned in the food contact area (direct and indirect) should be smooth, of a cleanable type and resistant against corrosive cleaning agents.