Electricity + Control October 2018

ANALYTICAL INSTRUMENTATION

In some cases, it may still be possible for food to make brief contact with the sensor and then return back into the process. In these cases, a hygienic sensor – with minimal crevices is a must. Physical hazards Physical hazards refer to potentially harmful, non- food particles that end up packaged with the food, often due to breakage of mechanical parts on the machine. While metal detectors can identify small pieces of metal before the product is distributed, other materials such as plastic and glass could slip by unnoticed, risking the health of the end custom- er if they consume a foreign object in their food. Sensors are not the only machine components from which pieces can break off and fall into food, but they are still important to consider. In environ- ments with frequent washdown, it is important to ensure that the product is rugged enough to withstand high temperatures and pressure, and a high chemical resistance may also be necessary to withstand caustic cleaning solutions. In these applications, look for an IP69K-rated sensor that has been thoroughly tested to withstand harsh environments. Solution: rugged sensors with all plastic housing

In addition, the material construction of the sensor makes a difference. While stainless steel might seem like the intuitive choice for food appli- cations, a metal photoelectric sensor will always still have plastic components (e.g. window, light pipes, etc.) that can become dislodged and fall into the process. Because sensors with metal housing still contain some plastic, this means they have plas- tic-to-metal joints that are attached either by ad- hesive and/or mechanical means. When subjected to temperature change – such as during cleaning – the different materials expand and contract at different rates, creating small air gaps which leave room for water ingress. On the other hand, a photoelectric sensor made entirely of plastic has plastic-to-plastic joints that are ultrasonically welded together, becoming a single piece. This reduces the risk of the sensor window becoming dislodged, and the sensor is better protected against the ingress of water.

The sooner food safety issues can be addressed and mitigated, the lower the risk of a large-scale recall.

Brandon Topham is a Director at RET Automation Controls.

8 Electricity + Control

OCTOBER 2018