What is the reason for the sudden failure of vegetable freeze dryer to cool during use? "Experience sharing"

　　I believe many customers have experienced some unknown malfunctions when using vegetable freeze dryer equipment, such as finding that the food, fruits, and medicines inside the vegetable freeze dryer have not changed much during use, and are still the same as before, as mentioned in the question, the vegetable freeze dryer does not cool during operation. If you also encounter this problem, don't worry, let the Dachang editor analyze the following reasons:

　　Vegetable freeze dryer is a method of pre cooling and freezing substances containing a large amount of moisture into a solid, and then directly sublimating water vapor from the solid under certain vacuum conditions. The substance itself remains in the ice shelf during freezing, and its volume remains unchanged after drying. Loose and porous ice absorbs heat during sublimation, causing the temperature of the product to decrease and slowing down the sublimation rate. In order to increase the sublimation rate and shorten the drying time, the product is heated appropriately. The entire drying process of the freeze dryer is carried out at a lower temperature.

　　The main unit (refrigeration unit) of the Dachang vegetable freeze-drying machine is not running properly

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

　　Causes:

　　The power is not connected and the voltage is too low.

　　Exclusion method:

　　According to the instructions of the freeze dryer, connect the power supply and reset the relevant contacts when the voltage is normal.

　　2、 The electric motor cannot move

　　Causes:

　　Due to excessive load on the refrigeration unit, far exceeding the rated power of the motor, the compressor does not operate or significantly slows down, causing the motor to produce a buzzing sound. At this time, the power should be immediately turned off for inspection.

　　Exclusion method:

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

　　3、 Water pressure alarm shutdown

　　Causes:

　　If the cooling water pressure of the water-cooled condenser is lower than the set value of the water pressure relay, the compressor of the freeze dryer will automatically shut down.

　　Exclusion method:

　　Eliminate the alarm, check the water pipe, restore the water pressure to normal, and restart the compressor.

　　4、 Oil pressure difference alarm shutdown

　　Causes:

　　1. Poor oil return, resulting in insufficient oil level in the compressor crankcase and inability of the oil pump to suction oil.

　　2. Dirty oil causes blockage of the oil pump filter.

　　3. The oil pressure differential relay is malfunctioning.

　　Exclusion method:

　　1. Replace the oil separator with a new one.

　　2. Change the oil and clean the oil filter.

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

　　5、 High voltage alarm shutdown

　　Causes:

　　1. The freeze-drying mechanism has too much refrigerant and high exhaust pressure.

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

　　3. There is a leak in the low-pressure section of the refrigeration pipeline, causing air to be sucked in.

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

　　Exclusion method:

　　1. Release some refrigerant.

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

　　3. Leak detection of refrigeration pipeline in freeze dryer.

　　4. Fully open the high-pressure exhaust valve or replace it with a new valve.

　　6、 Motor thermal protection shutdown

　　Causes:

　　The return air volume of the freeze dryer system is insufficient, and the motor has not received sufficient cooling.

　　Exclusion method:

　　1. Adjust the expansion valve, increase the circulation of the system, and ensure sufficient cooling of the motor;

　　2. Check if there is any blockage in the supply pipeline (including the supply shut-off valve, drying filter, solenoid valve, and filter screen before the expansion valve). If there is any blockage, it should be resolved accordingly.

　　3. Check for blockages in the return air pipeline and the suction filter of the compressor, and repair any blockages.

　　4. Check if there is a lack of refrigerant, and if there is a lack of refrigerant, it needs to be replenished.

　　7、 The performance of the condenser deteriorates

　　Causes:

　　1. The incomplete defrosting of the condenser in the freeze dryer leads to a decrease in heat transfer performance.

　　2. The product loading exceeds the set value.

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

　　Exclusion method:

　　1. Defrost thoroughly and drain the water completely.

　　2. Do not exceed the maximum capture capacity.

　　3. Slow down the heating speed.

　　8、 Insufficient or no cooling capacity

　　Causes:

　　1. The expansion valve is opened too much, and at this time, the temperature of the shelf or water vapor condenser has not dropped to the set value, while the compressor is severely frosted.

　　2. The expansion valve is too small to lower the temperature, but the compressor temperature is high and there is no frost at the suction valve. The suction pressure and the evaporation temperature corresponding to the shelf or water vapor condenser are much lower than the temperature of the shelf or water vapor condenser.

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

　　4. Insufficient refrigerant charging results in the inability to lower the temperature, low suction pressure, and no frost formation at the suction valve.

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

　　Exclusion method:

　　1. Adjust the expansion valve.

　　2. Clear the refrigeration system and replace the components.

　　3. Fill refrigerant.

　　4. Replace the paper pad or valve plate.

　　9、 Low pressure of thermal oil

　　Causes:

　　There is air in the thermal oil.

　　Exclusion method: Turn on the circulation pump, connect one end of the hose to the heat transfer oil exhaust port and the other end to the balance tank, open the exhaust valve, and exhaust the air in the pipeline.

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

　　Causes:

　　1. Insufficient flow rate of heat transfer oil (decreased performance of heat transfer oil and circulation pump).

　　2. The temperature probe is malfunctioning.

　　3. Air has mixed into the thermal oil.

　　Exclusion method:

　　1. Replace the thermal oil and repair the circulation pump.

　　2. Replace the temperature probe.

　　3. Exhaust air.

　　11、 Switching of circulating pump

　　Causes:

　　1. Unstable pressure.

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

　　3. The pressure relay is damaged.

　　Exclusion method:

　　1. Exhaust air.

　　2. Replace or repair the circulation pump.

　　3. Replace or repair the relay.

　　Dachang vegetable freeze-drying machine

　　The common faults and troubleshooting of vegetable freeze dryers are fundamental tasks, and the normal operation and extended service life of freeze dryers will create more benefits for enterprises. This article combines the actual debugging and maintenance of freeze-drying machines by customers, analyzes common faults in refrigeration systems, circulation systems, vacuum systems, and proposes corresponding solutions. It is hoped that this article will be helpful to vegetable freeze-drying machine manufacturers.

　　The above is an explanation of why the fruit and vegetable freeze dryer suddenly does not cool during use. The methods and solutions are for reference only. If you have more detailed and better solutions, please contact us to share and discuss together!

　　Reminder: Common faults and troubleshooting of vegetable freeze dryers are fundamental tasks, and the normal operation and extended service life of freeze dryers will create more benefits for enterprises. This article combines the actual debugging and maintenance of freeze-drying machines by customers, analyzes common faults in refrigeration systems, circulation systems, vacuum systems, and proposes corresponding solutions. It is hoped that this article will be helpful to manufacturers of fruit and vegetable freeze-drying machines.

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