Material Drying
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PET dehumidifying drying dew point
Problem Phenomenon
After PET preforms are dried according to the process, white haze still appears, and the measured dew point of the drying air is only -25℃
Cause Analysis
PET moisture content requirements are demanding (below 50 ppm for bottle grade), and the dehydration limit of dry air at a dew point of -25℃ is insufficient to press the moisture content down to the required value
Solution
The dryer dew point must be stable below -40℃; the molecular sieve is regenerated and replaced regularly; a dew point meter monitors online with an alarm set; after adjustment, take consecutive samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
The first indicator of PET drying is the dew point, and -40℃ is the threshold for bottle-grade production; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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