Pay attention to the below items when to 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. Every kind of pump has a definite work pressure scope. For example, the 2BV series water ring vacuum pumps' work pressure scope is 760mmHg~25mmHg(abs). Among the scope, the suction capacity changes accompanying the work pressre of the pumps (the details refers to the curve). The steady work pressure scope of the pump is 760~60mmHg. Thus the work point of the pump in the scope is more proper and it is not able to work in vacuum scope from 25 to 30mmHg for a long time.

    3.The vacuum pump should be able to pump all the gases producing in the technics process of the vacuum equipment when it works under its work pressure scope.

    4.To select the crrect combination of the vacuum pumps. Because the vacuum pump may 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 to satisfy the requirements. Otherwise, some vacuum pumps can't work under the atmosphere and need the pre-vacuum, some vacuum pumps' discharge pressure is lower than the atmosphere and need the fore pump. As a result, it is necessary to assemble them for usage. the
common used combination is roots pump and water ring vacuum pump(JZJ2B package unit).

    5.Sometimes, the vacuum equipment requires to prevent the oil pollution. If the vacuum equipment requires without oil pollution strictly, it should select various the pumps without oil. Such as, the water ring vacuum pump, the molecular sieve adsorbing pump, the spraying hydronium pump, and low temperature pump etc.. But if the requirement without oil is 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, it is also able to satisfy the cleaness requirements.

    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 gases media's characteristics. 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.How about the oil vapor blew off from the vacuum pump influences to the environment? If it is not allowed, you can select the vacuum pump without oil, or discharge the oil vapor outdoor.

    8.How about the libration while the vacuum pump working influences to technics process and the environment? If the technics process requires about this aspect, you should select the pump without libration or adopt some measures to prevent the libration.

    9.The price of vacuum pump and the cost of the pump's operating and maintainance.

Sequence to select the water ring type vacuum pump

One, to confirm the pump's type
The type is definited by the working suction capacity, the vacuum or the discharge pressure.

　　Pay attention to the two aspects as bellow during the pump's work:：

• It is better to make the pump work in the higher efficiency region. In other words, make the pump run in the vacuum critical scope or the discharge pressure critical scope.
• It should avoid the pump to work near the limited vacuum or the max discharge pressure. Because the pump works in this area, its efficiency is very low and running is unsteady. Furthermore, it is easy to produce the libration and noise. To the vacuum pump with high vacuum degree works in this area, sometimes the kavitation will occur. And the kavitation obvious sign is the pump's libration and screaming. As a result, the kavitation will damage the pump casing and impeller so that the pump will be out of work.

According to the principle above, when the vacuum or discharge pressure is not required high, the single pump is preferential; When the vacuum or discharge pressure is required higher and the single pump is not satisfied the condition, or, the larger suction capacity is required in the higher vacuum (i.e. the pump curve is flat in the higher vacuum region), the dual-grades vacuum pump is the better; When the vacuum is required above －710mmHg，the water ring vacuum pump with ejector or the Roots pump and water ring vacuum pump unit is the best.

Two, to select the vacuum pump according the suction capacity of the system　
When select the pump type firstly, it is necessary to confirm the type according to the suction capacity of the system.
The caculation about the suction capacity and suction time of the vacuum pump refers to the vacuum caculation on 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.