Dairy processing: Aseptic processing and packaging systems
Pressure differential recorder controllers

General conditions

• Sensors are clean and in good mechanical condition
  • the design should allow easily dismantling of the sensors for inspection
• The indicating and recording unit is housed in an appropriate moisture proof enclosure
• Inter-wire the pressure differential recorder controller with the flow diversion device such that divert occurs when the sterilized product pressure in the regenerator does not exceed the pressure on the raw side of the regenerator by at least 14 kPa (2 psi)
  • in "milk-to-heat transfer medium-to-milk" type regenerators, the divert occurs when the sterilized product pressure does not exceed the heat transfer medium pressure by at least 14 kPa (2 psi)

A PLC can be used to control the pressure differential in lieu of a pressure differential controller as long as the same control conditions are respected such as inter-wiring with flow diversion device, pressure indicating and recording capabilities, and set-point indication.

Pressure gauges may be used to verify the pressure display for the pressure differential recorder controller.

• Pressure gauges are clean and in good condition

Location

2 types of regeneration are used in APPS:

1. product-to-product regenerators
2. product-to-water-to-product regeneration systems

The product-to-water-to-product regeneration system is often preferred for some products because it allows more even heat transfer and prevents burn-on.

Product-to-product regenerators:

• install the raw product sensor between the feed pump and the raw product inlet to the regenerator
• install the sterilized product sensor at, or downstream from, the sterilized product outlet of the regenerator

Product-to-heat transfer medium-to-product regenerators:

• install the raw side pressure sensor in the water loop after the water pump (location of highest media pressure in the loop)
• install the sterilized side pressure sensor in the product line at the sterilized side outlet of the regenerator (location of lowest sterilized product pressure)

Specifications

• Use a circular chart that makes one revolution in not more than 12 hours and that is graduated for a maximum record of 12 hours
  • if operations extend beyond 12 hours, use a 24-hour chart that provides an equivalent level of accuracy and clarity
• Ensure the chart positive drive mechanism is equipped with a system to prevent slippage or manual rotation (for example, a pin to puncture the chart paper)
• Use charts that correspond with the chart number displayed on the identification plate of the pressure differential recorder controller
• Ensure chart scale divisions do not exceed 14 kPa (2 psi) on the working scale of not more than 140 kPa (20 psi) per 25 mm (1 inch)
• Pens record the raw side pressure and the sterilized side pressure or the pressure differential
  • electronic data collection, storage and reporting of pressure differentials, with or without hard copy printouts, can be used provided the electronically generated records meet the minimum criteria for safety thermal limit recorder charts

Calibration

• Test the accuracy of the pressure display and recorder, and the differential controller divert function, at least every 6 months and whenever the controller is adjusted or repaired
• Check pressure gauges, if used, for accuracy upon installation, at least every 6 months and whenever gauges are adjusted or repaired
• Use the testing methods in Critical process test procedures – Pressure differential.
  • keep records of testing results and any corrective actions

Sealed

• Seal the pressure differential recorder-controller adjustments/legal panel