Detailed introduction
　　I. Summary of Water-sinking Tanks
　　The principle of water tank is the same as that of alcohol tank. It is a common technological step in the extraction of traditional Chinese medicine. The water tank corresponds to the alcohol tank. The ethanol extract of traditional Chinese medicine is concentrated and then water is added to the ethanol extract at room temperature or low temperature for water sedimentation. Water is used as a solvent to dissolve the active ingredients in the concentrated solution and as a precipitator to precipitate some impurities in the ethanol extract. Water sedimentation is a method of removing impurities from extracts by water precipitation. It removes impurities, reduces the dosage of drugs, achieves the characteristics of refinement and easy preparation, so that the traditional Chinese medicine decoction can be made into Chinese patent medicine. The water sink tank is a kind of alcohol-water extract or concentrated liquid of Chinese traditional medicine to be prepared. After adding 1-4 times of water, the water insoluble substances in the solution are removed by static sedimentation. After recovery and removal of ethanol, the water is diluted to a specified depth, and then sealed and sterilized after filtration. Its basic principle is to refine the finished product and improve the quality of the finished product by utilizing the properties of some active ingredients of traditional Chinese medicine which are both soluble in ethanol and water. The principle of precipitation with water is to use alcohol body fluid to compose a certain concentration of ethanol in order to achieve the purpose of removing impurities. In general, when the depth of ethanol reaches 50%-60%, the impurities such as starch can be removed; when the depth of ethanol reaches 75%, the impurities such as protein, polysaccharide and inorganic salt can be removed. Thus, the active ingredients such as alkaloids, glycosides, amino acids and organic acids, which are soluble in water and alcohol, are retained. Therefore, alcohol precipitation method is used for water extraction and water precipitation method is used for alcohol extraction, so the structure and principle of alcohol precipitation tank and water precipitation tank are the same.
　　CHARACTERISTICS OF WATER SUBSIDENCE TANKS
　　The tank is welded by three layers of stainless steel. The inner liner is polished with high quality stainless steel SUS316L/304, which meets the requirements of food and pharmaceutical hygiene level. The sandwich adopts SUS304 stainless steel, and the sandwich is equipped with stainless steel guide plate, which is conducive to the diversion of cooling water. External welding filling stainless steel outsourcing, polyurethane insulation, conducive to heat preservation, to prevent the rapid loss of heat, environmental protection and energy saving. The water sinking tank has the functions of cooling, heat preservation and stirring. The tank body is designed with process nozzles such as material inlet, pure water outlet, outlet, sampling port, heat exchange inlet and outlet. The design of automatic control system for water sink tank includes process control of feeding, discharging, temperature control and mixing, which reduces labor intensity and makes the sedimentation process fully automatic. Setting clear liquid outlet can adjust the amount of liquid according to the height of the page. The supernatant outlet is an angle to the cylinder body and can rotate 360 degrees at the same time. The tube is equipped with a guide gear. The rotation direction of the outlet tube is adjusted by the handwheel outside the tank top to ensure that the supernatant is basically pumped out, and the sediment (including flocculent) is not pumped out. The top of the tank is equipped with mirrors and spotlights to inspect the precipitation and discharge of the liquid in the tank. Set up a long mirror on the tank wall to facilitate the observation of the boundary page between precipitation and supernatant, so as to observe the separation of precipitation. In order to achieve good separation effect, the bottom of the submerged tank is usually conical with a conical angle of 90 ~120.