The CIP program control system may be simple or complex, depending upon the nature of the application.   Fully "automated" control of the cleaning program is preferable to manual control and should include variables of rinse and drain times, recirculation time, temperature, concentration, and flow-rate, the latter via either instrumentation or engineering design.  If the process involves considerable air-operated valving and requires the operation of pumps and other processing equipment, then the program control system selected must be capable of handling the entire requirement. 

* CIP program controllers of a decade ago were generally cam-timers or drum-type stepping switches used in combination with relay-logic based control systems. 

* The CIP program controller of the 1990's is more commonly a micro-processor or computer based system in the form of dedicated CIP controllers, based on micro-processors, "Off-the-shelf" Programmable Logic Controllers (PLC's) configured and programmed to establish the desired operation. or large power-full DCS systems.  Combinations of PLC's and DCS systems are now very common.  These systems have many other capabilities not possible with hard-wired systems, including analog input and output, PID control, ASCII output to display messages, RS232 ports to allow communication with other PLC's and computers, and many other modules available to increase application capabilities. PLC's are generally programmed in Ladder Logic not too different from the wiring for relay-logic systems of the past. Anyone that can troubleshoot a hard-wired system can be trained to troubleshoot a PLC.  Personal Computers (PC's) may be used as the interface to a PLC or DCS based system, and may, with the appropriate I/O (Input/Output) devices actually control the cleaning system. 

* The CIP program controller may be  time-based or flow-rate and volume based (with tank wash drain periods still time-based). Athe photograph at the left shows several retrun line sensors of sanitary design.   Variables to be controlled include ... 

        -       Time, via internal timers (fixed or as Process Variables) 
        -       Volume ... via vortex shedding meters. 
        -       Flow ... via analog control loops based on the flow rate sensed by the above meter. 
        -       Temperature ... via Resistance Temperature Devices (RTD's) inputs to a PLC , computer, or  independent temperature control instruments. 
        -       Pressure ... via P/I transducers and inputs to a PLC or computer. 
        -       Conductivity or resistivity measurements for chemical concentrations ... via the appropriate sensing devices and interface to the PLC or computer. 

Matrix programming is preferable for both the CIP program and the associated programs for sequential operation of process valves, pumps, agitators, etc., if required. A typical program for cleaning tanks via spray application of the solution often combines a 3-burst pre-rinsing and 2-burst post-rinse with wash and acidified rinse by recirculation. A line program applicable to cleaning any combination of piping, pumps, and valves in a continuous circuit most comonly applies a continuous rinse, and CIP Supply pump operation is continuous from the beginning to the end of the program.  It is necessary only to change the Drain Valve position to recirculate or divert to drain. 

The CIP program can be monitored from beginning to end and certain check-points established to verify specific operations. Some common "end-point control" checks might include ... 

• No Return flow ... a signal based on a probe in the return line checking for return flow immediately following the first portion of the pre-rinse. Failure to achieve return flow indicates improper connections, or an inoperative pump or valve.
• Delay-to-temperature control logic is arranged to stop program advance at the beginning of the wash cycle until all of the solution in the circuit reaches the desired cleaning temperature, assuring washing for the proper time at the desired temperature.
• Low chemical concentration ... a conductivity cell or resistivity sensor may be used to monitor for a minimal "threshold level" to assure that chemical feed systems are operative, that the supply is adequate, etc.

CIP Program Data Acquisition 

The 3-A Accepted Practice, as applied in the dairy industry and often used as a guideline by other users of Clean-In-Place technology, states that "Solution temperature shall be automatically controlled by the use of a temperature regulator with a response range of plus or minus 5( F."  This is loosely adhered to, if at all, as there is no requirement for a specific cleaning temperature, for any application.  This same Standard requires a "recording thermometer having a scale range of 60-180( F. with extension of scale on either side permitted. Graduated in time scale divisions of not more than 15 minutes. Between 110-180 F., the chart shall be graduated in temperature divisions of not more than 2( F., spaced not less than 1/16" apart, and be accurate within 2( F. plus or minus. The sensor shall be protected against damage at 212 F., and the sensing element of the recording thermometer shall be located in the return solution line". 

The intent of this requirement is to provide a chart record of the cleaning time and temperature relationship, in recognition that the effectiveness of this essentially chemical procedure is determined by time, temperature and solution concentration. 

Hydraulic performance is equally important. Cleaning solution may remain stagnant in the return system, at wash temperature while the return pump is air-bound for prolonged periods of time, and this condition ultimately impacts on the performance of the supply pump, also.  A temperature recorder alone may suggest a suitable recirculation period.  A recorder chart and recording instrument including a temperature pen and a pump discharge pressure recording pen permits operating, maintenance and quality control personnel to evaluate the hydraulic performance of the system, in addition to knowing the recirculating time and temperature. 

Recent revisions of the FDA regulations for Dairy CIP systems now permit the substitution of equivalent (and superior) recording devices. 

Desirable CIP Data Logger Capability 

• Graphic print-out/screen display should includes operator's initials.
• Text description of circuit name and mode of operation (i.e., CIP, sanitize, etc.).
• Listing of alarm messages that occurred during the cycle.
• Date, start time, and CIP System number
• A screen display of a currently operating cycle should includes current, real time numeric display of all plotted variables and current step description.
• A desirable capability is to print-out the raw numeric data for any cycle, plotting four (or more) variables in proper relationship on a large, easily readable, color graph format against time. Printed variables should be listed with engineering units and scale.