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Three common questions and answers for freeze-drying machines
2026-06-04
1. Insufficient vacuum degree or slow pumping speed
This is one of the most common malfunctions of freeze-drying machines, which directly affects the efficiency of sublimation drying.
Possible reasons: Vacuum system leakage (such as aging or damage to door seals and sealing rings); Vacuum pump oil aging, deterioration or low oil level; The vacuum pipeline is blocked or the valve is not tightly closed.
Solution: First, check and clean all sealing rings, and replace them promptly if aging or cracks are found; Check the oil level and quality of the vacuum pump, and supplement or replace the vacuum pump oil if necessary; Use helium mass spectrometer leak detector or pressure holding test to identify leaks in pipelines and connections; Ensure that the cold trap has been lowered to below -50 ℃ before vacuuming to effectively capture water vapor.
2. The sample may collapse, bubble, or clump after drying
This usually means improper setting of drying process parameters or inaccurate determination of freeze-drying endpoint.
Possible reasons: Heating up too quickly or applying vacuum too early during a drying stage may cause the ice crystals to melt before fully sublimating; Insufficient secondary drying (analytical drying) resulted in high residual moisture inside the sample, causing moisture absorption and agglomeration after discharge.
Solution: Strictly follow the principle of "freezing first, then vacuuming, and slowly heating up" to ensure that the sublimation temperature is lower than the eutectic point of the sample (usually 5-10 ℃ lower); Accurately determine the endpoint of freeze-drying, combined with vacuum degree, sample state, and temperature curve for comprehensive judgment; Standardize the implementation of gradient secondary drying, gently remove residual bound water, and ensure that the powder is loose and dry.
3. Poor cooling effect or unstable temperature control
Temperature is the key to successful freeze-drying, and temperature fluctuations can lead to uneven drying and even product deactivation.
Possible reasons: refrigeration system malfunction (such as refrigerant leakage, compressor damage); Excessive dust on the surface of the condenser leads to poor heat dissipation; Temperature sensor malfunction or temperature controller failure 1.
Solution: Check if there is any leakage in the refrigerant pipeline, confirm the working status and pressure value of the compressor are normal; Regularly clean the surface of the condenser to ensure good ventilation in the environment where the equipment is located; Use a multimeter or calibrated reference thermometer to check the temperature sensor, and calibrate or replace it if necessary; Check if there is an open or short circuit in the heating element.
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