CIP: The Industrial-Grade Dishwasher

Q: What components comprise the CIP control system?

A: At the heart of the control system is the programmable automation controller (PAC) that runs the program(s) controlling the operation. The devices (i.e. valves, pumps, sensors, meters, etc.) on the CIP skid are wired to the PAC as analog or digital inputs/outputs (I/O) points. Tethered to the PAC is the operator interface, or human machine interface (HMI), which is used to monitor the CIP system, select the circuit to clean, and to start/stop/abort the process. Additional components include the chart recorder and the pin-sheet.

Chart recorders are used to monitor and record the system’s key performance indicators (KPI) as they pertain to temperature, level, pressure, conductivity, and flow. Pin-sheets are used to document the system’s circuits, phases, and device sequences. The Information Age has enveloped both the chart recorder and pin-sheet. Many systems now feature “chartless” electronic records and trending. Refer to Figure 1. These trends provide the same information as a chart but with the added advantages of being retrieved, viewed, and stored with the click of a mouse. Additionally, the use of electronic signatures permits supervisory “sign-off” of the overall effectiveness of the cleaning process. Industry regulations such as the Pasteurized Milk Ordinance recognize the benefits of electronic chart recorders. Additionally, pin-sheets are being improved upon functionally by their electronic counterparts. Electronic pin-sheets, through the use of spreadsheet software or the HMI, have been embraced as a valuable tool for supervisory level staff to create and modify the CIP process.

Q: What defines the CIP automated process?

A: In many ways, the CIP process can be likened to the batch process used to make a product. Batching is comprised of recipes, steps, ingredient additions, and timed holds/agitations sequences. Similarly, CIP processes are comprised of circuits, phases, steps, and sequences. Circuits can be categorized as to the function and/or equipment they are cleaning. Some common circuit types can be Line, Tank, Tank and Line, or a specific piece of equipment like Filler, for example. Circuits are comprised of cycles or phases. Common phases include Prerinse, Wash, Postrinse, and Sanitize. These are easily remembered by thinking how the dishwasher cycles (pre-rinse the plates to drain before washing, wash, rinse-off the detergent, then sanitize). Phases are made up of steps. Steps might include rinse to drain, pump down, caustic wash, acid wash, fresh water rinse, and air blow. The specific sequence executed involves the “pinning” of the devices through the use of the pin-sheet.

The pin-sheet is a spreadsheet that serves as the master schedule for the CIP process. The pin-sheet identifies the system name, the circuit name, and contains detailed sequence information per its phases: step description, number, time, targeted supply line temperature and flow rate, and return line conductivity. Furthermore, the pin-sheet contains a bit position within the sequence word(s) for every device residing on the CIP skid and within the field. This bit position represents the “device pin” for which the sheet gets its name.

Recall that a primary advantage of modern CIP systems is the integration of the CIP PAC with the production system PACs. The pin-sheet has the ability to reach across into the production controller to set and cycle process equipment as part of the CIP program.

Q: How is the data in the pin-sheet brought into the PAC?

A: The fields on the pin-sheet are translated into programming parameters that are downloaded into the PAC. The PAC executes the CIP program based on this data. The data takes on two forms: discrete (digital 1s and 0s) and analog values (percentages, flow rates, time, temperature, etc.).