TL;DR
Fouled heat exchanger plates reduce heat transfer and can prevent the pasteurizer from reaching the required temperature. Verify CIP effectiveness and plan a manual plate clean if needed.
What you might see
- pasteurization temperature not reaching setpoint
- heat exchanger pressure drop rising
- longer time to reach pasteurization temperature at startup
- product temperature dropping mid-run
Likely causes
Protein denaturation deposits on plate surfaces from high-temperature product
Mineral scale from hard water in the heating medium circuit
CIP cleaning time or temperature insufficient to remove protein fouling
Plate gasket leakage causing product and heating medium cross-contamination
Required tools
- Pressure gauges (plate PHE inlet and outlet)
- Temperature recorder log access
- Plate cleaning brush set
- Chemical-rated gloves and eye protection
- LOTO kit
Safety first
- Hot product and hot water are present in the heat exchanger. Confirm CIP is complete and the system is cooled before opening the plate pack.
- Chemical cleaning of heat exchanger plates uses caustic and acid solutions. Wear chemical-rated PPE.
- Any pasteurization cycle where the process temperature was not met must be treated as a potential under-pasteurization event. Quarantine and test product per the site's food safety plan.
Procedure
- 1
Review the heat exchanger log temperatures over the last week. A downward trend in heat transfer rate confirms fouling.[1]
- 2
Check the differential pressure across the heat exchanger. Rising pressure drop confirms deposit buildup on plate surfaces.[1]
- 3
Verify the last CIP cycle achieved the specified temperature, time, and chemical concentration for protein removal.
- 4
Inspect the product outlet temperature from the regeneration, heating, and cooling sections. A specific section with poor performance narrows the fouled zone.
- 5
Check the heating medium supply temperature and flow rate. A drop in hot water or steam supply can mimic fouling symptoms.
- 6
If CIP is verified correct and fouling persists, plan a manual plate clean: open the plate pack, inspect each plate, and clean with an approved acid and caustic sequence.
- 7
After manual cleaning, perform a pressure test on the gaskets before reassembly.
Sources
Tetra Pak Tetra Pak A3 / Flex Pasteurizer / HTST System general technical documentation, Tetra Pak
Tetra Pak A3 / Flex HTST pasteurizer general plate heat exchanger maintenance and CIP procedures (general)
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