Thorough cleaning is a price of doing business in food processing. Food manufacturers should analyze clean-in-place (CIP) processes for efficiency improvements just as might be done with the primary process. Improving efficiency while maintaining food safety requires both careful analysis and a flexible control system. One manufacturer “found” eight hours of availability per week by optimizing their CIP recipes, reducing cleaning time while improving food quality and safety.
Cleaning process equipment in place generally requires four basic tasks or routes. These are combined into a loop from the CIP system or skid, through the process and back to the CIP system. These are:
• Route within the process equipment to be cleaned,
• Route for returning used solution from the process,
• Cleaning solution source, and
• Cleaning solution return destination.
When cleaning solution does not pass through a tank, the control engineer might treat the two theoretical routes through the process equipment as one. The routes form a loop from the cleaning source, through the process equipment, to the return destination.
The cleaning solution source route may contain instrumentation to monitor the quality of the delivered fluid such as monitoring temperature, flow rate, and conductivity. The cleaning solution return destination may include instrumentation to allow recycling of CIP fluids. Equipment is generally exercised to enhance cleaning. For example, valves may be cycled or pulsed. Maintaining proper flow rates often requires that the route within the process equipment be adjusted to clean one portion of the total route and then another.
Determining the cleaning methods of a CIP system includes defining:
• What is to be cleaned by a cleaning procedure?
• What must be interlocked to safely allow cleaning in parallel with processing activities?
• What items can be cleaned in parallel or must be cleaned serially?
• How individual items are to be exercised (or not) while they are being cleaned?
The myriad of requirements makes CIP a very complex process, often more complex than the process used to make the products. While CIP control may be mostly manual—f raught with opportunity for human error, a programmed system is complex and rigid. A better, but less often used, alternative is recipe managed CIP control.
In programmed CIP, a programmer builds a program that includes all of the routes, interlocks, cleaning orders, and equipment exercises required to complete the cleaning methods. Lists of timers or pinning charts allow the end user to modify the duration of cleaning methods, providing some flexibility. Changing the cleaning methods themselves usually requires modification of programming by the original or another competent programmer.
The complexity of CIP requires complex software. Complex software is generally more rigid and difficult to optimize without creating software bugs. In a validated system, any modification to the CIP requires expensive and time consuming re-validation of the process.
The traditional approach of custom programming and pinning charts has been the gold standard of CIP control for a long time, up until now.
Recipe Managed CIP
The ISA-88 standard (S88) can help resolve many of these issues. In a paper entitled “Clean-in-Place Made Simple” delivered to the World Batch Forum in May of 2010, John Parraga of Rockwell Automation showed how to apply S88 to CIP. Applying S88 allows the control engineer to separate control of the equipment from how the equipment is to be used, i.e. “What the equipment can do,” from “What to do with the equipment.”
In an S88 compliant control system, coordination control occurs at runtime. Instead of constructing complex scenarios for arbitration, allocation, and interlocking or imposing the limitation of cleaning the entire process cell at once, CIP can start on portions of a process cell while other portions are finishing a batch of product. Improvement in equipment utilization increases available production capacity.
What is cleaned, in what order it is cleaned, and how it is cleaned are managed in an S88 flowchart-style recipe. Process knowledgeable personnel can modify these recipes with a minimum of training, without modifying the existent, validated, controller programming. Compliance increases because recipes execute consistently under the S88 management software package.
Capable S88 batch management packages allow users to define values to collect from the process control and incorporate into a permanent record. Reporting monitors compliance with the approved cleaning procedures. Historical cleaning batch records are useful in many ways related to maintaining safe, quality food production.
Because the same equipment control and coordination control are used for the cleaning processes as are used for the production processes, enhancements to the operator interface (HMI) are possible. Operators who are aware of coordination conflicts can determine an appropriate course of action and, with appropriate permission, enact it.
A Real-World Example
In 2011, ECS Solutions received a contract from Unilver to provide a control system for a “super kitchen” that included 40 tanks and other major pieces of equipment, 500 valves, 30 pumps, 30 agitators, and 170 instruments. The equipment was piped in what S88 calls a network structure, making it capable of producing batches of several different products simultaneously. The product included dairy components, making cleanliness even more important to product quality and food safety.
ECS provided a recipe managed CIP system based on S88 Builder. The initial cleaning recipes were developed based on calculations done by the process designer and on ECS’ and the customer’s experience. These recipes were tested during commissioning to provide ample, but not necessarily optimal, cleanliness.
After commissioning and without ECS’ involvement, a customer team began the process of optimizing the CIP processes. Equipment was broken down and tested with ATP (adenosine triphosphate). The team followed an iterative process of modifying the flowchart-style master recipe in the batch management package, running the “worst case” product, and re-testing the equipment with ATP. Individual component cleaning times increased when necessary to improve cleaning. Times decreased when possible to save time and maintain cleanliness. Throughout, the focus was impeccable food safety, accomplished as efficiently as possible.
Maintaining product quality and food safety requires consistency and accountability. The Unilever process engineer responsible for the system explains that the old, pinning chart based CIP system required CIP specialists. “CIP specialists stepped around, each cleaning differently. Cleaning took longer with more labor. Now, because the look and feel of running CIP is like running a batch, our production operators do the cleaning. The recipe gives us efficient, consistent cleaning. Reports are printed by the operators on conclusion of the cleaning, signed, and kept.” Reporting includes the four factors identified as key to good CIP—time, temperature, flow, and conductivity.
Unilever stays focused on system cleanliness. The responsible process engineer continues, “We continue to monitor cleanliness using ATP.” Should testing indicate a problem, he can modify the CIP himself. He can modify how a certain component (control module or CM) operates within a certain task (equipment module or EM). He can also easily modify the recipe, changing the procedure or simply changing the time spent on any portion.
Features identified as important to effective management of the process line cleaning include:
• The operators can clean the entire process cell, a unit, and all associated equipment, or an individual piece of the process;
• A Unilever process engineer can configure the operation of any component within a task without the assistance of a programmer;
• Likewise, a Unilever engineer can quickly customize a recipe on his or her own, for example, to add a quick acid rinse; and
• Recipes are password protected, so operators clean consistently as engineering and management have determined.
A recipe managed CIP system allows non-programmer, process knowledgeable personnel to define safe and effective cleaning procedures. Cleaning activities strictly follow the defined procedures and reports provide accountability and historical records. Recipe managed CIP is both a safe and efficient solution formaintaining food quality and food safety.
Matheny is president of ECS Solutions, Inc., the developer of S88 Builder and a certified member of the Control System Integrators Association (CSIA), www.controlsys.org, a global non-profit professional association that seeks to advance the industry of control system integration. Matheny, a member of the ISA-106 Procedure Automation for Continuous Process Operations committee, can be reached at Tim.Matheny@ECSSolutions.com.