Is your legacy PLC failing you on food hygiene?

The food processing sector has lagged behind many others in adopting new technologies and there are still many older legacy systems running a lot of processes. These increasingly present a risk to business as parts become redundant, the skills required to support them disappear and the downtime required to maintain them proves increasingly expensive. Keeping abreast of technology can result in better process control, diagnostics and reporting.

Today’s programmable logic controller (PLC) hardware is now compact, faster and powerful than ever. Software has become more accessible – moving from a requirement for coding experts prior to the introduction of IEC 61131 open international standard in 1993 to fully structured programs that are supportable and in modern, user defined data type (UDT)-based language. And web-server integration in HMIs offers secure access to remote users and engineers, resulting in cost-effective 24/7 support.

Out with the old…

The food sector is under increasing pressure to embrace technology developments. And, with an uncertain time ahead in terms of food standards for British food manufacturers, being on top of efficiency and hygiene for the production line is vital.

Advances in visual displays, logic controllers and connectivity to analytical instruments has opened up the control spectrum. Introducing new processor and control displays can simplify an operation, reducing operator error and providing the means to record events critical to control, quality and hygiene.

Most legacy systems continue to do the job that they were originally installed to do. This is often one-dimensional and does not realize the potential that modern PLCs can have to link functions of the automation system with business systems and the production environment, improving production and maintenance.

For many of PVSL’s food and drink sector customers, a key area for production and maintenance is hygiene during cleaning-in-place (CIP) on the production line. A recent project for a UK bakery was focused on upgrading the PLC to improve data collection and diagnostic of the CIP process as well as improving water and energy use. The client stipulated zero impact installation, so no stoppage of the plant during installation from a production viewpoint.

The client’s legacy PLC and Mimic panel, which covered several processes, had become difficult to operate and yielded little data to validate quality and hygiene of the plant. It also relied on paper records which was time intensive, inefficient and costly.

The initial review identified several upgrade opportunities for the line, including options for conductivity meters for better logging and compliance checks, the fitting of modern loadcell amplifiers for the product tanks as well as upgrading all the product tank instruments and replacement of pumps and drives to introduce efficiencies in power consumption.

However, it was the upgrades to the PLC itself that yielded the real benefits. A new stainless-steel control panel was installed along with a similar panel for pneumatics. The new processor and control display panel connected directly to the old field cabling and was introduced so as to avoid production down-time.

A fully structured text program was introduced and, once retraining was undertaken, assisted the operator or maintenance engineer to identify problems and also opened up a whole new database of plant variables critical to quality and hygiene. This included carefully monitoring flow and pressure to validate accurate use of water and chemical consumption.

New features included real-time alarm and event logging along with trending data for a better view of performance alongside quality and chemical usage-related records. CIP validation was provided by conductivity to measure detergent strength and pH monitoring in rinsing. As a result, water usage was reduced through CIP optimization by around an estimated two-thirds.

The new HMI and PLC allows remote support for the client, saving engineering travel and line down-time. It also now allows collection of data for management and quality reporting. For hygiene, it trends all data from validated cleaning cycles, including detergent strengths, temperatures and rinsing values.

Edward Ralph is director of PVSL UK. This article originally appeared on Control Engineering Europe’s website. Edited by Keagan Gay, digital media & production coordinator, CFE Media, kgay@cfemedia.com.

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