Because these systems are fully automatic, including the operation of the bleeder valves, maintenance of the system is often neglected. Failure to adequately maintain the system can result in failure of bleeder valves, vent valves and system controls to operate properly. When these types of retort control systems are encountered the investigator must observe the operation of the system through several cycles to insure that all control valves are operating properly, that bleeder valves are fully open and functional during the venting and thermal processing cycles, and that scheduled process time and temperature parameters are being met. Cam operated control systems have been used by U.S. and European equipment manufacturers to automatically control retort processing including processing temperature, pressure, processing times and cooling times. In these systems a cam is cut out of plastic, metal or some other durable material.
Care has to be taken to cut the correct profile in the cam to provide the correct thermal process.
As the cam wears the profile may change, changing the thermal process. European manufactures such as LaGarde and Stock have used card readers to control retort temperature, retort pressure and process timing. In these systems a card made of plastic, metal or paper is either cut or punched to a certain profile for each thermal process. The card is then placed in a card reader. In the LaGarde system the card is read by a light source.