Student Handout- Module Number Seven (7) - Thermal Processing System Components,

Instrumentation, and Equipment, and Process Room Operation 

Thermal Processing System Components, 

Instrumentation, and Equipment, and Process 

Room Operation 

Temperature Indicating Devices - Mercury-in-glass (MIG) thermometer serves as the 

reference instrument for LACF; Alternative devices such as thermocouples or resistance 

temperature devices (RTD) or digital temperature gauges (DTG) may be used; Each retort is 

required to have at least one MIG thermometer, DTG, RTD or equivalent thermometer or 

electronic device (PLC). 

Mercury-In-Glass/Equivalent Thermometer- Easily readable to 1°F-MIG range not to exceed 

17°F/inch graduation-Installed where easily read-Installation location varies depending on retort 

type-Tested for accuracy when installed and annually-Defective devices must be repaired or 

replaced. 

Records must specify the following information-Identification of the device (MIG/DTG/RTD)-

Manufacturer of the device-Identification of the reference device-Equipment and procedures 

used for check-Date and test results-Name of person or facility performing test-Date of next test 

(optional)-Each device must have a tag, seal, or other means to identify it and correlate it with 

the accuracy check record-A record is necessary for documenting the accuracy of the reference 

device-For acidified foods, no specific requirements on the type of device – should still test for 

accuracy. 

Temperature/Time Recording Devices

Low-acid foods: Required for each retort; Can be combined with the steam controller to be a 

recorder controller; Provides a permanent record of temperature and time for the thermal 

process 
 

 

The temperature/time recorder should agree as close as possible with MIG/RTD but never

higher- Accuracy to 1°F-Pen arc adjusted properly-Time of day set properly-Prevent 

unauthorized changes with a lock or notice. 

Chart-Type Recorders - Use appropriate chart paper; Graduations not to exceed 2°F within a 

range of ±10°F of the process temperature; Scale not to exceed 55°F/inch within ± 20°F of the 

process temperature. Continuous line or multipoint plotter - Installation location of recorder 

bulb or sensor will vary based on the type of thermal processing system. 

Each retort must have an automatic steam controller. 

Instrument Air Supply Requires: Adequate filter system; Clean, dry air at the proper pressure; 

Independent air supply system. 
 

Pressure Gauges - Scale should not exceed 2 PSI; Useful when processing with overpressure, 

pressure cooling and as safety device. 

Timing Devices - Wristwatches are not permitted; Use analog or digital clock 

Located where easily and accurately read. 

Maintenance - The regulations require that each thermal processing system be examined at 

least once a year. 

Steam Supply: Steam is the most common heating medium; Supply of steam to thermal 

processing area must be adequate to bring the retort up to process temperature. 

Valve Types and Uses - Gate or Ball: Used on vents for rapid discharge and are full flow; Air 

and water lines connected to the retort must be equipped with a globe valve or other suitable 

valve to prevent leaking into the retort; Double block and bleed configurations or three-way 

valves are often installed on water or air lines used for cooling. 
 

 

 

 

Bleeders - Small openings on retorts used for: Circulation of steam; Air removal that comes in 

with the steam; Condensate removal. Required on external wells when the MIG/DTG and 

recorder probes are installed in an external well. 

Mufflers - Used on vents and bleeders to reduce noise; Must not reduce air removal or interfere 

with heat distribution; Cartridges must be inspected and replaced as needed. 

Posting of Thermal Processes - Operating processes and procedures must be posted in 

conspicuous place or be readily available to the operator and CSI. 

A system for product traffic control must be established to prevent containers from bypassing 

the retort. Each crate or at least one container in each crate must be marked with a heat 

sensitive indicator. 

Each container must be coded; Codes are embossed or imprinted; May be legibly marked on a 

securely affixed container label. 

Code Requirements: Product unless printed on the container; Year packed; Day packed. 

Initial Temperature (IT) - Temperature of the coldest component in the product when thermal 

process begins. Must be determined for coldest container in retort.