1.The working pressure of the liquid ring vacuum pump should satisfy the required pressure of the vacuum equipment. For example, when the vacuum drying process requires the vacuum degree at 10mmHg, then the water ring vacuum pumps you choosed must be able to reach the limited vacuum at 2mmHg. , Generally speaking, the limited vacuum degree of the water ring vacuum pump you choosed must be 5 or 10 times higher than the working vacuum degree of the vacuum equipment.
2. To select the work point of vacuum pump correctly. Each kind of water ring vacuum pump has a definite work pressure scope. For example, the work pressure scop of the 2BV series water ring vacuum pumps is 760mmHg~25mmHg(abs). Among this range , the suction capacity changes along with the work pressre (about the he details, refer to the performance and curve ). The steady scope of the work pressure is 760~60mmHg. Thus the work point of the water ring vacuum pump in the scope is more proper and it can not work in vacuum scope from 25 to 30mmHg for a long time.
3.The liquid ring vacuum pump should be able to pump all the gases produced in the technics process of the vacuum equipment when it works under its work pressure scope.
4.To select the correct combination of the vacuum pumps. Because the water ring vacuum pump can suction various gases media. Sometimes, to chooses one kind of vacuum pump are not able to satisfy the pumping requirements, so it needs to equiped with several kinds of vacuum pumps together. Otherwise, some vacuum pumps can’t work under the atmosphere and need the pre-vacuum. The discharge pressure of the vacuum pumps is lower than the atmosphere and a fore pump is needed. As a result, it is necessary to assemble them for usage. the common combination is putting several Roots vacuum pump and a water ring vacuum pump together.(for example: the ZJPS series roots pump package units).
5.Sometimes, the vacuum equipment requires to prevent the oil pollution. If the requirements are strict, it should select various vacuum pumps without oil. Such as, the water ring vacuum pump, the molecular sieve adsorbing pump, the spraying hydronium pump, low temperature pump etc. But if the requirements are not strict, it is also able to choose the vacuum pumps with oil and take some measures to prevent the oil pollution. Such as, to add the cold trap, the baffleplate, or the oil-proof trap.
6.To consider the gases element if it contains the coagulable steam or dust and if it is inculde corrosive gas etc. After that, to choose the proper vacuum pump according to the characteristics of the media. Further, if the gases contains steam, granulars dust and corrosive element, it should assemble the assistant facilities on the inlet pipes, such as, the condenser and the dust catcher.
7. The influences of the oil vapor blew off from the vacuum pump to the environment. If it is not allowed, you can select the vacuum pump without oil or discharge the oil vapor outdoor.
8.The influences of the vibration of vacuum pump to the technics process and the environment. If it is not allowed, you should select the water ring vacuum pump without vibration or take some measures to prevent the vibration.
9.The price you also need to consider , transportation, operation and maintainance of the vacuum pumps.