Dairy Establishment Inspection Manual – Chapter 14 - Aseptic Processing and Packaging Systems
1.14.09 Flow Diversion Device (FDD)

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The FDD is set up to control the direction of product flow according to the establishment of safe conditions within the processing system. It is located after the cooling section and before the filler or aseptic surge tank, and is designed to divert flow away from the filler or aseptic surge tank automatically.

1.14.09.01 General Conditions

The FDD must be of a design that permits sterile operations, and that can positively and effectively prevent potentially unsterilized product from contaminating the fillers or aseptic surge tank(s). Since there are many possible valve designs, numbers and arrangements, acceptance should be determined by the responsible agency.

FDDs must be equipped with a proper control panel where the control functions and relays are installed. This control panel may be part of a universal panel unit. This panel shall be free of any device or switches that may override the control functions and jeopardize the safety of sterilized product. On valves that have external solenoids, the air lines must not have quick release couplings.

Installations on aseptic processing and packaging systems often have complex operating parameters for the FDD that can only be handled by a micro-processor or programmable logic controller (PLC). A PLC or micro-processor control used strictly for FDD function is not required to meet the standards of Task 1.14.11.07 Program Logic Controllers and Computers, but all valve functions must pass the required tests.

The FDD and the return lines shall be constructed of stainless steel and must be clean and in good mechanical condition. Valves, plunger seals and O-rings must also be clean and in good mechanical condition. Stem length of the valves shall be non-adjustable to insure that proper seating of the valves is not disturbed. If the stem has a threaded attachment, a locking pin or other equivalent locking mechanisms shall be used to prevent any misalignment. Air to the FDD must be clean and unrestricted.

1.14.09.02 Return Line

The FDD shall have a pipeline that directs the flow of potentially unsterile product safely away from fillers and /or aseptic surge tanks. Any subsequent valves installed on this line must be configured in all positions to allow free flow from the FDD, without blocking the flow or creating excessive back pressure on the FDD. A flash cooler may be installed on the return line to prevent injury to bystanders during divert events when pre-sterilizing the system.

1.14.09.03 Location

The FDD must be located after the final cooling section and before the fillers or aseptic surge tanks.

1.14.09.04 Fail Safe Divert Capability

The FDD shall automatically assume the divert position (so product will not go to aseptic surge tanks or fillers) under at least one of the following conditions for indirect heating systems:

  1. The product temperature in the sensing chamber drops below the specification in the scheduled process
  2. The differential pressure between sterilized product and unsterilized product or heat transfer media is less than 14 kPa (2 psi) in the regenerator
  3. Adequate product pressure is not maintained in the holding tube to prevent boiling (less than 69 kPa (10 psi) above the boiling pressure of the product in the holding tube)
  4. Loss of electrical power or compressed air to the FDD solenoids
  5. Excessive flow rate is detected for systems utilizing a magnetic flow meter as a flow control device
  6. Pressure in the surge tank drops below the value specified in the scheduled process, in systems where there is only one surge tank or no capability to send product directly to a filler (prevents sterile product from entering unsterile tank). Note: In systems where more than one surge tank exists, product would not need to be diverted but could be directed to the sterile surge tank

The FDD shall automatically assume the divert position (so product will not go to aseptic surge tanks or fillers) under at least one of the following conditions for direct heating systems:

  1. The product temperature in the holding tube drops below the specification in the scheduled process
  2. The differential pressure between sterilized product and unsterilized product or heat transfer media is less than 14 kPa (2 psi) in the regenerator
  3. Adequate product pressure is not maintained in the holding tube to prevent boiling (less than 69 kPa (10 psi) above the boiling pressure of the product in the holding tube)
  4. Loss of electrical power or compressed air to the FDD solenoids
  5. For steam infusion systems, loss of pre-determined parameters (temperature, pressure level, etc. as determined by the qualified authority) at the steam infusion chamber exits
  6. For steam injector systems, improper differential pressures across the steam injectors at the holding tube (a 69 kPa (10 psi) drop across the injector is required)
  7. Excessive flow rate is detected for systems utilizing a magnetic flow meter as a flow control device
  8. Pressure in the surge tank drops below the value specified in the scheduled process, in systems where there is only one surge tank or no capability to send product directly to a filler (prevents sterile product from entering unsterile tank). Note: In systems where more than one surge tank exists, product would not need to be diverted but could be directed to the sterile surge tank

The FDD shall be installed with position detection capabilities to provide an electrical signal to the STLR flow indicating lights and event pen.

After an event causing a flow diversion, all product contact surfaces downstream from the holding tube shall be re-sterilized, as outlined in the scheduled process (see also Task 1.14.11.04 Thermal Limit Controller Sequence Logic). The re-sterilization process must include the fillers and aseptic surge tanks, unless there is a properly designed aseptic barrier to act as a leakage barrier (see Task 1.14.09.05 Leak Detect and Appendix 19 - 10).

Plant records shall indicate the test results for valve operation at the required intervals and must show satisfactory follow-up on out of specification findings.

1.14.09.05 Leak Detect

Aseptic processing and packaging systems where the filler continues to operate from an aseptic surge tank while the FDD is in the divert position, must use a properly designed aseptic barrier to separate sterile product from potentially non-sterile product. (see Appendix 19 - 10).

The aseptic barrier shall be located between the FDD and the blocking valve for the aseptic surge tank.

The barrier(s) may include one or more steam blocks, but must include a resistance thermal device (RTD) or other acceptable temperature sensor at the lowest level of the barrier to detect barrier failure due to steam loss or fluid leakage into the barrier. Barrier failure detected by the temperature sensing device must trigger an alarm system to alert the operator to the alarm condition, immediately initiating a shut down sequence for the processing system as specified in the scheduled process.

After a barrier failure condition, the fillers, aseptic surge tanks and lines, and aseptic processing system must be completely drained of product and all equipment must be re-sterilized before processing and filling may resume. Implicated product should be placed on "hold" until its sterility is assessed. This failure must be noted in the operator's log book and a process deviation report must be completed, which includes the date and time of the process deviation, investigation into the cause of the process deviation and action taken both on product and other corrective measures.

1.14.09.06 Device/Panel Sealed

The FDD control panel and valve position detector cover(s) must be sealed to prevent unauthorized tampering or adjustments. The valve position sensing detectors, valve actuating solenoids and relays shall be sealed. If a PLC or micro-processor is used to control valve functions, access to programming functions shall be sealed.

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