In the distributed system a PLC or microprocessor can be used for independent control of each retort system. The retort microprocessor is then used to supply information to a systems computer which captures all retort data for storage and printing. The systems computer in turn is used to store process programs and to program the logic controls of the microprocessor. During inspections of lacf manufacturers using computers to control thermal processes or to control other factors critical to the process the investigator must determine the functions of the computer system. In many cases lacf manufacturing firms will not have on hand detailed information covering the development and validation of the software and microprocessors used on their retort systems.
Many firms buy the microprocessors as black boxes from the equipment vendor.
The investigator must then determine the functions of the control system in as much detail as possible. It is important to remember that computer controlled retort systems must function to provide for control of the thermal process, the same as any other type of control system. Each retort system is still required to be equipped with a temperature recorder as per the lacf regulations. If the firm has a schematic drawing of the control system this should be obtained or the investigator may prepare a simplified schematic drawing, which will be helpful in explaining the system operations. If the firm does not have detailed information on the microprocessor control system the investigator should obtain any limited information that is available.