Tunnel Pasteurizer PU Values Are Too High or Too Low

Verify the PU measurement, then check product entry temperature, conveyor residence, zone temperatures, spray coverage, nozzle blockage, recirculation flow and container position. Average tunnel temperature can hide cold lanes.

Place affected product on hold and follow the validated food-safety plan. Isolate heat, pressure, chemicals and rotating equipment before inspection; only an authorized process authority may release product after a critical deviation.

Locate the fault

• Data loggers show different PU by conveyor lane
• Packages overheat or remain underprocessed
• Zone temperature is stable but product temperature is not
• Results change with conveyor loading

Inspection sequence

1. Hold affected product under the scheduled process and quality plan
2. Verify calibrated PU loggers and consistent container placement
3. Map product-temperature histories by lane and position
4. Measure conveyor speed and actual residence including stops
5. Inspect spray pattern, nozzles, strainers and recirculation flow
6. Trend zone temperatures and incoming package temperature

Corrective work

• Clean and balance spray distribution
• Restore conveyor speed and stop handling to the validated process
• Repair zone heating, cooling and controls
• Repeat a qualified temperature-distribution and PU validation

Operating records and follow-up

• Inspect spray coverage at startup
• Trend lane-specific performance
• Maintain strainers and pumps
• Control product entry temperature
• Revalidate after conveyor or zone changes

Equipment details: Tunnel Pasteurizer.