What is the reason why the vegetable freeze dryer suddenly stops cooling during use? "Experience Sharing"

　　I believe that many customers have more or less unknown problems with the vegetable freeze-drying machine when using the vegetable freeze-drying machine equipment. For example, during use, they find that the food, fruits, and medicines in the vegetable freeze-drying machine have not changed, and are still the same as before. As the title says, the vegetable freeze-drying machine does not cool during operation. If you also encounter this kind of problem, don’t worry, let the editor of Dachang analyze the following reasons:

　　The vegetable freeze dryer is to freeze substances containing a large amount of moisture into a solid by cooling them in advance, and then directly sublimating the water vapor from the solid under certain vacuum conditions. The substance itself remains in the frozen ice shelf, and its volume remains unchanged after drying. The loose porous ice absorbs heat during sublimation, causing the temperature of the product itself to drop and slowing down the sublimation speed. In order to increase the sublimation speed and shorten the drying time, the product must be appropriately heated. The entire drying process of the freeze dryer is performed at a lower temperature.

　　Dachang vegetable freeze-drying machine host (refrigeration unit) is not operating normally

　　1. The refrigeration compressor cannot start (the reasons for not working are as follows)

　　Cause:

　　The power supply fails and the voltage is too low.

　　Troubleshooting:

　　According to the instructions of the freeze dryer, turn on the power and reset the relevant contacts if the voltage is normal.

　　2. The motor cannot drag

　　Cause:

　　Due to the overload of the refrigerator, which far exceeds the rated power of the motor, the compressor does not operate or slows down significantly, and the motor makes a buzzing sound. At this time, the power should be turned off immediately for inspection.

　　Troubleshooting:

　　Check whether there is power in the three phases and whether the power supply voltage of the freeze dryer is normal.

　　3. Water pressure alarm shutdown

　　Cause:

　　When the cooling water pressure of the water condenser is lower than the setting value of the water pressure relay, the freeze dryer compressor automatically stops.

　　Troubleshooting:

　　Fire the alarm, check the water pipes, restore the water pressure to normal, and restart the compressor.

　　4. Oil pressure difference alarm and shutdown

　　Cause:

　　1. Poor oil return results in insufficient oil level in the compressor crankcase and the oil pump cannot absorb oil.

　　2. Dirty oil causes the oil pump filter to become clogged.

　　3. The oil pressure difference relay fails.

　　Troubleshooting:

　　1. Replace the oil separator with a new one.

　　2. Change the oil and clean the oil filter.

　　3. Replace the oil pressure difference relay with a new one.

　　5. High pressure alarm shutdown

　　Cause:

　　1. The freeze dryer has too much refrigerant and the exhaust pressure is high.

　　2. The cooling water temperature is high, the flow is insufficient or the water condenser is scaled.

　　3. There is a leak in the low-pressure section of the refrigeration pipeline and air is sucked in.

　　4. The high-pressure exhaust valve is not fully opened or damaged, resulting in poor exhaust.

　　Troubleshooting:

　　1. Release part of the refrigerant.

　　2. Use cooling water whose temperature and flow rate meet the requirements and clean the water condenser.

　　3. Check the refrigeration pipeline of the freeze dryer for leaks.

　　4. Open the high-pressure exhaust valve fully or replace it with a new one.

　　6. Motor thermal protection shutdown

　　Cause:

　　The air return volume of the freeze dryer system is insufficient, and the motor is not fully cooled.

　　Troubleshooting:

　　1. Adjust the expansion valve to increase the circulation of the system to fully cool the motor;

　　2. Check whether the liquid supply pipeline is blocked (liquid supply cut-off valve, dry filter, solenoid valve, filter in front of expansion valve). If blockage occurs, solve it accordingly.

　　3. Check whether the return air pipeline and the suction filter of the compressor are clogged, and repair them if they are clogged.

　　4. Check whether there is a lack of refrigerant. If there is a lack of refrigerant, add refrigerant.

　　7. Condenser performance deteriorates

　　Cause:

　　1. The condenser of the freeze dryer is not defrosted completely, causing the heat transfer performance to deteriorate.

　　2. The product filling volume exceeds the set value.

　　3. The heating amount for sublimation of the product is too large and the sublimation is too fast.

　　Troubleshooting:

　　1. Defrost thoroughly and drain the water cleanly.

　　2. Do not exceed the maximum water capture volume.

　　3. Slow down the heating speed.

　　8. Insufficient 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.

　　3. The refrigeration system of the freeze dryer is blocked, such as filter blockage, valve not opening, solenoid valve failure, expansion valve blockage, etc.

　　4. 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.

　　5. The paper pad 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.

　　9. Thermal oil pressure is low

　　Cause:

　　There is air in the thermal oil.

　　Troubleshooting method: Turn on the circulation pump, connect one end of the hose to the heat transfer oil exhaust port, and connect the other end to the balance barrel. Open the exhaust valve to exhaust the air in the road.

　　10. Large temperature difference between inlet and outlet of thermal oil

　　Cause:

　　1. The heat transfer oil flow is insufficient (the performance of the heat transfer oil decreases and the performance of the circulation pump decreases).

　　2. The temperature measuring probe is faulty.

　　3. Air is mixed into the heat transfer oil.

　　Troubleshooting:

　　1. Replace the heat transfer oil and repair the circulation pump.

　　2. Replace the temperature probe.

　　3. Exhaust air.

　　11. Circulation pump switching

　　Cause:

　　1. The pressure is unstable.

　　2. The circulation pump of the freeze dryer is damaged.

　　3. The pressure relay is damaged.

　　Troubleshooting:

　　1. Exhaust air.

　　2. Replace or repair the circulation pump.

　　3. Replace or repair the relay.

　　Dachang vegetable freeze dryer

　　Common faults of vegetable freeze dryers and their elimination are basic tasks. The normal operation and extended service life of the freeze dryer will create more benefits for the enterprise. This article combines the actual practice of customers debugging and repairing freeze dryers, and analyzes common faults in several aspects such as refrigeration systems, circulation systems, and vacuum systems, and proposes corresponding solutions. I hope this article will be helpful to manufacturers of vegetable freeze dryers.

　　The above is an explanation of the reasons why the fruit and vegetable freeze-drying machine suddenly stops cooling during use. The methods and solutions are for reference only. If you have more detailed and better solutions, you can contact us so that we can share and discuss them together!

　　Warm reminder: Common faults of vegetable freeze dryers and their elimination are basic tasks. The normal operation and extended service life of the freeze dryer will create more benefits for the enterprise. This article combines the actual experience of customers debugging and repairing freeze dryers, and analyzes common faults in several aspects such as refrigeration systems, circulation systems, and vacuum systems, and proposes corresponding solutions. I hope this article will be helpful to manufacturers of fruit and vegetable freeze dryers.

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