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At present, most vacuum pumps used in vacuum precooling devices are rotary vane vacuum pumps. Although the rotary vane pump with air ballast device can pump out the mixed gas containing a small part of water vapor and a large amount of permanent gas, in the process of vacuum precooling, due to the evaporation of water inside the vegetables, a large amount of water vapor will be pumped into the rotary vane pump, and the water vapor will condense in the pump cavity. This will lead to the emulsification and deterioration of the lubricating oil of the vacuum pump, seriously affect the limit pressure that the vacuum pump can reach, reduce the lubrication performance, intensify the wear, fail to work normally, and even seriously rust the pump body, rotor and other parts, resulting in the scrapping of the whole machine. Therefore, punook recommends the application of Roots vacuum pump in vacuum precooling device.

Precooling after harvest is an effective method to keep vegetables fresh and delay their aging and deterioration. For different vegetables, four methods can be adopted: cold air precooling, differential pressure precooling, vacuum precooling and water precooling. Roots vacuum pump vacuum cooling has been widely used in the field of food industry. Compared with traditional cooling methods such as air blowing and water immersion, vacuum precooling can greatly shorten the cooling time and make the internal temperature field of food more uniform. Obviously, from the perspective of preservation, vacuum precooling device is the most ideal vegetable cooling and refrigeration equipment at present

The vacuum cooling system includes a vacuum chamber, a bracket and a vacuum pump, wherein the vacuum pump is a Roots vacuum pump. During the operation of roots pump, attention shall be paid to: ① ensure that the inlet water temperature of vacuum pump is as close as possible to the design operation condition and the water volume is sufficient. ② Ensure the cooling water circulation of the vacuum pump, otherwise the unit will shut down due to the overheating protection of roots pump when running for about 1H.

Product features of Roots vacuum pump：

1.Motor diversity

The motor of each punoclotz vacuum pump can be air-cooled or water-cooled to ensure the normal use of customers

The pump is made of aluminum alloy or cast iron to realize the advantages of fast heat dissipation and strong corrosion resistance

2.Simple structure and convenient maintenance

The rotor profile makes the design of the pump more compact by carefully designing the circular arc rotor

The pumping effect is more outstanding, and the pumping speed is greatly improved compared with other manufacturers at the same level

The maintenance is also very convenient and the maintenance cost is very low

3.Clean vacuum

There is no medium in the roots pump cavity that can react chemically with air

Ensure that the pumped gas is not subject to secondary pollution and realize high clean vacuum

4.Universal booster pump

Roots pump, also known as booster pump, can be connected with screw pump, discharge pump, water ring pump and slide valve pump

Molecular pumps and other pumps form a pump group, which greatly improves the pumping rate and vacuum degree

Under normal circumstances, the vacuum can be more than 10 times higher!

It can be seen from the above contents that compared with the rotary vane vacuum pump, the vacuum chamber pressure of Roots vacuum pump basically drops to the specified value within the same time, and the two effects are basically the same. However, in the experiment of a small number of vegetables, because the roots pump can bear a certain amount of water vapor, there is no problem of lubricating oil emulsification, and will not affect the operating conditions of the vacuum pump, it can avoid adding refrigeration system. The application of Roots vacuum pump in the vacuum precooling device not only prolongs the service life of the vacuum pump, but also saves the cost.