Food & Drink Process & Packaging Issue 7 2016 - Page 19

Electrodes Glass diaphragm electrodes use a reference electrode, suspended in a buffer solution of pH7 - that is compared to the measuring electrode and as such this design is used for a wide range of applications. For more robust applications single element electrodes made from enamel-coated steel or a polymer that use pH sensitive coatings are also available. B├╝rkert uses a modular system that allows process engineers to build the most suitable pH sensing system, depending on the application. A variety of probes designed to operate in varying conditions and media can be combined with PT1000 temperature sensors and connected to a transmitter / controller such as the Type 8619 multiCELL. Combined with a choice of fittings and sealing materials as well as EHEDG certification, the product range can be specified to suit most applications within the food industry. In general glass pH electrodes are not suitable for food applications due to the risk of broken glass fragments contaminating the process. Further- more, many designs of pH electrode need to be removed from the process stream before the CIP process can be completed which requires expensive retraction systems to be employed, creating extra work and inconvenience for the end user. A variety of probes and temperature sensors designed to operate in varying conditions and media can be connected to a transmitter / controller such as the Type 8619 multiCELL seen here mounted into a stainless enclosure. One solution could be the Type 8201 pH measuring system, which employs a hygienic, robust and glassfree design that can withstand high temperatures and can be sterilised in situ. In addition, the smooth enamel external surface of the probe inhibits the process medium from sticking to it and is very easy to clean. By using industry standard signals, these pH sensors can either be integrated into an existing process control system or used in conjunction with other control components. This can provide localised feedback for a closed loop control system, for example to ensure the correct dosing of a product with pH sensors both before and after the process. Material specification of the sensor body and the sealing components can also play an important role in the performance of the pH sensor within the wider process control environment. This is particularly true when dealing with extremes of pH which can be highly reactive and corrosive. Sensor manufacturers with specialist knowledge in this area should be available to support customers to ensure that both process and hygiene control are properly managed. The wid H