Communications

The CIP automation system must be in communication with the processes
being cleaned. In many systems, the controller for CIP may be separate
from those being used by the other parts of the process. The
communications must include:

• Ensuring that both systems are ready prior to starting
• Passing parameters for confirmation of cleaning
• Communications of completeness of the CIP cycle

One typical way to divide the duties between the CIP controller and the
process controller is shown in Table 3-1.

Sequences for CIP

The key sequences used for CIP are:

• Preparation of Cleaning Solution
• Distribution of Cleaning Solution

Key design decisions to be made include:

• Will the system be allowed to distribute fluid to multiple systems
  at once?
• How will arbitration between systems be handled?
• What are the specific completion criteria for each step?

Control Loops in CIP Systems

The control loops used within CIP systems are generally simple, independent,
PI or PID control loops. The only real complexity is determining the
expected state of each control loop during each part of the CIP cycle.

Flow control and pressure control loops are generally PI control loops
handled with variable-speed drives on the CIP supply and/or return
pumps.

More advanced ratio-control strategies can be employed in the preparation
step to ensure precise control of the final cleaning fluid concentration.

Temperature control loops are generally handled using PID controls on
jacketed tanks during preparation and storage, and heat exchangers at the
point-of-use for cooling the fluids.

Tuneables for CIP

It has been noted above that control loop setpoints must change from step
to step in the process. During "cleaning development," these setpoints are
often adjusted frequently. Those doing the cleaning development treat
them as "tuneable" parameters. Once these parameters are established,
they must be "locked down" for use by operators. Again, integrated batch
management software can help simplify this work.