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When selecting a vacuum pump, the following points should be taken into consideration: 1. The operating pressure of the vacuum pump must meet the requirements regarding the ultimate vacuum and operating pressure of the vacuum equipment. For example, if a certain vacuum drying process requires an operating vacuum level of 10 mmHg, the ultimate vacuum capacity of the vacuum pump selected must be at least 2 mmHg; ideally, it should be able to reach 1 mmHg. Typically, the ultimate vacuum capacity of the pump chosen should be half to an order of magnitude higher than the operating vacuum level of the vacuum equipment. 2. Select the operating point of the vacuum pump correctly. Each type of pump has a specific operating pressure range. For example, the 2BA series water ring vacuum pumps operate within a pressure range of 760 mmHg to 25 mmHg (absolute pressure). Within this wide pressure range, the pumping speed of the pump changes depending on the pressure (for detailed details, refer to the pump’s performance curve); its stable operating pressure range is 760 mmHg to 60 mmHg. Therefore, it is more appropriate to select the pump’s operating point within this range, rather than allowing it to operate continuously at 25–30 mmHg. 3. At its operating pressure, the vacuum pump should be capable of removing all the gas generated during the process in the vacuum equipment. 4. Combine the vacuum pump correctly. Due to the selective pumping capability of vacuum pumps, sometimes a single pump is not sufficient to meet the pumping requirements; it is necessary to combine several pumps, with each complementing the others, in order to fulfill these requirements. For example, a titanium sublimation pump has a high pumping speed for hydrogen but cannot pump helium, while a triode-type sputtering ion pump (or a diode-type asymmetric cathode sputtering ion pump) has a certain pumping speed for argon. By combining the two, a better vacuum level can be achieved in the vacuum system. Additionally, some vacuum pumps cannot operate at atmospheric pressure and require pre-evacuation ； Some vacuum pumps have an outlet pressure lower than atmospheric pressure, requiring a pre-pump; therefore, these pumps need to be used in combination. 5. Requirements of vacuum equipment regarding oil contamination. When the equipment requires absolutely no oil, various oil-free pumps should be chosen, such as water ring pumps, vertical oil-free vacuum pumps, sputter ion pumps, screw vacuum pumps, etc. If the requirements are not strict, a model equipped with an oil pump, along with some oil contamination prevention measures such as cold traps, baffles, and oil traps, can also meet the requirements for a clean vacuum environment. 6. Determine the composition of the gas to be pumped; check whether it contains condensable vapors, particulate dust, or corrosive substances, etc. When selecting a vacuum pump, it is necessary to know the gas composition and choose an appropriate pump for the gas to be evacuated. If the gas contains vapors, particles, and corrosive gases, it is advisable to consider installing auxiliary equipment such as condensers and dust collectors on the inlet pipeline of the pump. 7. What is the impact of the oil vapor emitted by vacuum pumps on the environment? If the environment must remain free from contamination, an oil-free vacuum pump can be chosen, or the oil vapor can be vented outdoors. 8. Does the vibration generated by the vacuum pump during operation have an impact on the manufacturing process and the surrounding environment? If the process does not permit it, a vibration-free pump should be selected or vibration prevention measures should be taken. 9. The price of the vacuum pump, as well as the costs associated with its operation and maintenance. Selection of Water Ring Vacuum Pumps I. Determination of Pump Type The type of pump is primarily determined by the volume of air required for operation, the level of vacuum needed, or the exhaust pressure. When the pump is in operation, two aspects need to be noted: it is desirable to operate within the high-efficiency range, that is, in the region of critical vacuum or critical exhaust pressure. Operation near the maximum vacuum level or maximum exhaust pressure should be avoided. Operating within this range is not only extremely inefficient, but also results in unstable operation, prone to vibration and noise. For vacuum pumps operating at relatively high vacuum levels, cavitation often occurs when they operate within this range. A clear indication of this phenomenon is noise and vibration inside the pump. Cavitation can cause damage to components such as the pump body and impeller, resulting in the pump failing to function. Based on the above principles, when the vacuum level or gas pressure required by the pump is not high, a single-stage pump should be preferred. If the vacuum level or exhaust pressure is high, a single-stage pump often fails to meet the requirements. Alternatively, if it is necessary for the pump to handle a large volume of gas at high vacuum levels, that is, if a relatively flat performance curve at high vacuum levels is required, a two-stage pump can be used. If a vacuum level of above –710 mmHg is required, a water ring-atmospheric pump or a water ring-Rotary vane vacuum unit can be used as the vacuum pumping device. II. Selecting the vacuum pump based on the air volume required by the system After initially determining the type of pump, it is also necessary to choose the specific model of the vacuum pump according to the air volume demanded by the system. For the selection of the pumping speed and the calculation of the pumping time for vacuum pumps, please refer to the vacuum calculation formulas on our company’s website. In the face of various types of water ring vacuum pumps and compressors, we have compiled their respective features below for reference when making a selection. Code, Main Features: Extreme vacuum level in mmHg, Operating vacuum level in mmHg, Pumping speed range in m3/min, Sealing type: SK. It is a single-stage water ring vacuum pump designed in China, featuring a simple structure and easy maintenance. At present, low-end water ring vacuum pumps will gradually be replaced by 2BV and 2BE series products. -700-300~-6500.15~120: Gaskets, mechanical seals. A two-stage water ring vacuum pump designed in China, equivalent to two SK water ring pumps connected in series; it offers higher vacuum levels and a greater pumping speed at high vacuum conditions compared to single-stage water ring pumps. At present, low-end water ring vacuum pumps will gradually be replaced by 2BV and 2BE series products. -735-300~-7001.5~30: Gaskets and mechanical seals of type 2BA utilize advanced Siemens technology; the pump has a coaxial design, is compact in structure, efficient, capable of achieving high vacuum levels, and offers stable performance. It will gradually replace the SK and 2SK series of water ring vacuum pumps with a pumping capacity of 0.4~6 m3/min. -735-300~-7000.45~8.33 Mechanical seal 2BE1 utilizes Siemens’ advanced technology; it features high efficiency, high vacuum levels, and stable performance, and will gradually replace the SK and 2SK series of water ring vacuum pumps with a pumping speed of 6~120 m3/min. -735 -640-300~-700 -300~-600, 5~120 gaskets, mechanical seals. The 2BE3 model utilizes Siemens’ advanced technology, offering high efficiency, high vacuum levels, and stable performance; it will gradually replace the SK series of water ring vacuum pumps with a pumping speed of 80~600 m3/min. -610 0~-60080~600: Gaskets and mechanical seals based on Soviet technology from the 1950s; they have low efficiency and high energy consumption, and were phased out in the early 1980s, being used mainly by existing customers. -640~-700-300~-650, 1.5~27 packers. Based on Soviet technology from the 1950s, they have low efficiency and high energy consumption; they were phased out in the early 1980s. They were mainly used for water intake in pumps, and have now been replaced by the 2BA series of water ring pumps. -600-300~-5500.33~0.66 gaskets