Reasons why the freeze dryer does not freeze dry

　　Freeze dryers have been widely used now, playing an outstanding role in food and chemical industries. Freeze dryer is a freeze-drying equipment that first freezes water-containing substances into a solid state, and then sublimates the moisture from the solid state into a gaseous state to remove the moisture and preserve the materials. The reason why the freeze dryer compressor is running normally but does not cool or does not cool enough mainly occurs in the refrigeration unit itself. Let’s analyze the reasons why the freeze dryer does not cool?

　　1. The refrigerant of the lyophilizer is not added enough. Under normal conditions, the sight glass should be able to see a completely transparent liquid flow of refrigerant. If there is thin frost at the expansion valve (capillary) and evaporator inlet, it means that the refrigerant is not enough and needs to be added.

　　2. If the expansion valve (capillary) is blocked by ice or dirt, it will cause the system resistance or flash gas to increase, causing the refrigerant flow rate to decrease, the suction pressure to decrease, and the evaporator cooling capacity to decrease.

　　3. The centrifugal fan of the air condenser is faulty, the cooling water output of the water condenser is insufficient or the water seepage temperature is too high, and excessive dust accumulation on the heat transfer surface of the condenser will cause the working pressure of the refrigerant exhaust pipe to increase, resulting in a reduction in cooling capacity.

　　4. If the suction pressure is high but the evaporator and condenser of the freeze dryer operate normally, and there is no obvious abnormality in the operating current of the compressor, it may be that the valve in the compressor or generator unit is damaged, or the cooling capacity is insufficient for actual use (i.e. the load is too high); if the operating current of the compressor is much lower than the factory nameplate value, it indicates that the suction reed in the compressor is damaged or the crankshaft is broken, and the compressor should be replaced.

　　Reasons and solutions for poor cooling effect of freeze dryer (insufficient cooling capacity or no cooling capacity):

　　Cause:

　　① The expansion valve is opened too large. At this time, the temperature of the shelf or water vapor condenser does not drop to the set value, and the compressor is severely frosted.

　　② The expansion valve is opened too small, and the temperature cannot drop at this time, but the compressor temperature is very high, and there is no frost at the suction valve. The evaporation temperature corresponding to the suction pressure and the shelf or water vapor condenser is much lower than the temperature of the shelf or water vapor condenser.

　　2. The refrigeration system is blocked, such as filter blockage, valve not opening, solenoid valve failure, expansion valve blockage, etc.

　　3. The refrigerant is insufficiently charged. At this time, the temperature cannot drop, the suction pressure is low, and there is no frost at the suction valve.

　　4. The paper gasket on the upper part of the compressor valve plate or the lower part of the cylinder is punctured or broken, or the compressor suction and exhaust valve plates are broken.

　　Troubleshooting:

　　(1) Adjust the expansion valve.

　　(2) Unblock the refrigeration system and replace parts.

　　(3) Charge refrigerant.

　　(4) Replace the paper pad or valve plate.

　　We will briefly introduce the reasons why the freeze dryer does not freeze dry. The above is the analysis of the reasons why the freeze dryer does not freeze. If you want to know more about it, you can pay more attention to us! We are a professional manufacturer of freeze dryers and suction dryers, including freeze dryers, adsorption dryers, air filters, pressure swing adsorption nitrogen generators and other products. If you need it, please feel free to contact us!

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