Pay attention to the following items when choose the water ring vacuum pumps:

    1.The working pressure of the vacuum pump should satisfy the required pressure of the vacuum equipment. For example, when the vacuum dryness technics requires the vacuum degree at 10mmHg, so the vacuum pump you chosed must be able to reach the limited vacuum at 2mmHg. Normally, the limited vacuum degree of the pump you choosed must be 5 or 10 times higher than the work vacuum degree of the vacuum equipment.

    2. To select the work point of vacuum pump correctly. Each kind of 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 the scope, the suction capacity changes accompanying with the work pressre (as the details, refer to the curve). The steady scope of the work pressure is 760~60mmHg. Thus the work point of the 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 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 vacuum pump can inhale various gases media. Sometimes, to chooses one kind of pump are not able to satisfy the pumping requirements, so it needs to fix several kinds of 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 pump and a water ring vacuum pump together.(for example: the JZJ2B series package units).

    5.Sometimes, the vacuum equipment requires to prevent the oil pollution. If the requirements are strict, it should select various 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 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 corrosive 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 libration of vacuum pump to the technics process and the environment. If it is not allowed, you should select the pump without libration or take some measures to prevent the libration.

    9.The price , transportation, operation and maintainance of the pump.

Sequence to select the water ring type vacuum pump

First, to confirm the type of the pump
The type is determined by the working suction capacity, the vacuum or the discharge pressure.

Pay attention to the two following aspects during the working of the pump:

• It is better to make the pump work in the higher efficient region. In other words, make the pump run in the vacuum critical scope or the discharge pressure critical scope.
• The pump should be avoided to work near the limited vacuum or the max discharge pressure. Because the pump works in this scope, its efficiency is very low and it works unsteadily. Furthermore, it is easy to produce the libration and noise. When the vacuum pump with high vacuum degree works in this area, the cavitation will occur. And obvious sign of the cavitation is libration and screaming. As a result, the pump casing and the impeller will be damaged by the cavitation so that the pump can't work.

According to the above principle , when the vacuum or the discharge pressure dose not require strictly, the single pump is preferential; If the vacuum or discharge pressure requires strictly and the single pump is not satisfied the condition. If the larger suction capacity of the pump is required in the higher vacuum (i.e. the part of the curve is flat in the higher vacuum region), the dual-grades vacuum pump is better. If the vacuum is required above －710mmHg,the water ring vacuum pump with an ejector or the JZJ series package unit is better.

Second, to select the vacuum pump according to the suction capacity of the system
After the pump is selected, it is necessary to confirm the concrete type according to the suction capacity of the system.
As the caculation about the suction capacity and suction time of the vacuum pump, please refer to the website :www.zbbz.com/gongshi.htm.

To the various water ring vacuum pumps and compressors, their technology parameter is collected as bellow in order to help the customer for choosing.