Best Practices of Automated CIP Systems

Proximity sensors – for all possible connections made at manual hook-up stations or “swing panels,” monitor points; used when initiating a cleaning circuit to verify all connections are properly in place for the specific circuit; used during the cleaning sequence as a safety monitor in the event a hook-up connection comes loose potentially spraying hot water and/or dangerous chemical solutions in an area.

Return side temperature transmitter – monitor point to insure the entire circuit is being cleaned at the required minimum temperature.

Return side liquid flow switch – monitor point to detect liquid is returning to the skid or kitchen from the circuit being cleaned. Typically used in conjunction with a timer creating a notification to the operator to stop the system and check for leaks or to check for incorrect circuit hook-up points.

Return side conductivity transmitters – monitor points to detect the absence or presence of chemicals. Rinse step times can be shortened when chemicals are not detected in the liquid returning to the skid or kitchen. Conversely, wash steps can be initiated sooner when chemicals are detected at the required concentration level in the return solution. In some applications a second, more sensitive, conductivity transmitter is used to sense the complete absence of chemicals in the final rinse step.

Return side turbidity meter – monitor point to detect the amount of solids in the return liquid stream; used to prevent liquids with high solids content from being directed into a recovery tank.

Process controller, such as a PLC or DCS – used to control the CIP steps together with checking for limits and alarms. This topic is covered in more detail below.

Human-machine interface (HMI) – the operator’s window into the system for control and monitoring the CIP process while operating. Again, this topic is covered in more detail below.

Performance-Packed CIP ­Controllers and HMI Platforms

CIP Control Platforms. A variety of PLCs and DCS platforms are well suited for controlling the range of simple to robust CIP systems. Simple CIP systems many times have a small stand-alone PLC or DCS controller. More operational complexity and additional instrumentation in the CIP system generally sets the need for more powerful controllers. Both PLC and DCS control platforms offer features attractive to users from different perspectives and preferences. The more common attributes of both platforms are ability to handle a variety of field devices found in today’s manufacturing environment; ability to interface to multiple device communication networks such as EtherNet/IP, ControlNet, DeviceNet, Profibus, AS-i Bus, Foundation FieldBus; ability to create structured code along with intuitive labels and tags within the programming; and closer integration with the HMI’s and data historians, event archivers, and relational databases (covered below).

Process controllers no longer live on the plant floor as separate “islands of automation.” Rather process controllers closely work together. Controllers are tightly integrated for both process and CIP. For high-availability and high-criticality applications, several process controller manufacturers offer redundant “hot-backup” configurations addressing the concerns over “single-point” hardware failure.

HMI. The user interface between the operator and the CIP process, commonly referred to as the HMI continues to be the most dominant window into the CIP process. The typical traditional HMI hardware platform was a stand-alone proprietary device or a Windows-based computer tied to either a proprietary bus or an Ethernet network. The preference in hardware platforms for HMIs is rapidly changing in food manufacturing. Thin clients and terminal servers are being used in both new applications and upgrades to legacy process control systems for CIP.

Thin clients are, generally, diskless processors that interface over an Ethernet network to a server where terminal server HMI software and application files reside. Thin client hardware requires minimal configuration compared to thick clients (traditional Windows-based computers or proprietary stand-alone HMIs). Different process and CIP screens can be simultaneously viewed by operators at different HMI workstations (thin clients).