Dairy Establishment Inspection Manual – Chapter 14 - Aseptic Processing and Packaging Systems
1.14.16 Aseptic Surge Tank

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The aseptic surge tank acts as a sterilized product balance tank for the fillers. This allows both the fillers and the aseptic processor to operate independently at their own flow rate.

The aseptic surge tank is installed downstream from the FDD. If the surge tank is protected by one or more aseptic barriers at the FDD, filling operations may continue from the tank while the Aseptic processor is in divert. Otherwise, the fillers and aseptic surge tank must also be emptied and re-sterilized after a divert event. (See Appendix 19 - 10).

The cleanliness and operation of the aseptic surge tank are important to prevent contamination of the sterilized product. Air over the product in the tank must be sterile.

1.14.16.01 General Conditions

The aseptic surge tank and associated valves, thermometers, etc. must be clean and in good condition. Instrumentation (temperature recording chart) must be installed to record and verify pre-sterilization of the tank before production commences.

1.14.16.02 Sterile Air

As product is withdrawn from the surge tank, negative pressure could develop in the tank, which could cause unsterile air and bacteria to be drawn in through joints, gaskets, etc. For this reason, the sterile air must be pressurized to prevent the development of negative pressure inside the aseptic surge tank.

In general, a processing authority establishes a venting or air purge schedule for the surge tank. Sterile air over-pressure must be maintained on aseptic surge tanks to ensure proper operation (i.e., product flow to the filler).

Sterile air is produced by incineration and/or filtration. Attention must be paid to how the establishment monitors sterile air over-pressure and the method of achieving sterility. If incineration is used, a temperature sensing device monitoring system is generally the easiest means. If a sterile filter is used, the specifications of the filter, filter location and number of filters must be monitored. Filter must be changed at intervals recommended by the manufacturer or process authority for their method of use and documented on the processing records.

A sterile air pressure controller or transmitter shall be used to monitor the sterile air pressure in the tank. Records of tests performed to determine the controller's/transmitter's calibration shall be maintained in the plant's files. Tests must include accuracy, upon installation and at an interval of at least every 6 months. The frequency of testing should be increased if the calibration is consistently found to be out of adjustment. If the calibration is consistently found to be out of adjustment, the reason for the calibration problems should be immediately identified and rectified.

Testing methods shall comply with the required standards. Follow-up on out of specification findings must be satisfactory.

If the sterile air pressure drops below the value specified in the scheduled process, the filler (s) shall cease operation, and the aseptic barrier located at the inlet of the unsterile tank shall be activated to protect the sterile product in the processing system from entering the unsterile tank. Filling operations may not resume until the aseptic surge tank, fillers and valves have been emptied and re-sterilized. If multiple aseptic surge tanks and fillers are used and the sterility of these is maintained, this requirement may not apply.

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