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Shandong Bozhong Vacuum Technology  Co., Ltd

 

Add:No.37 Bozhong Road,Ma Shang Town,Zhang Dian District,Zibo City,Shandong Province

Tel:+86-533-2530388
+86-533-2802841

Fax:+86-533-2530399

E-mail:bz@zbbz.com

 

TECHNICAL

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Selection of vacuum pump

Selection of vacuum pump

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Selection of vacuum pump, you need to pay attention to the following matters:

1,Vacuum pump working intensity of pressure should meet the requirements of the limitation vacuum and working intensity of pressure of vacuum device. Such as: a vacuum drying process requirements 10mmhg working vacuum degree, ultimate vacuum of the selected vacuum pump is at least 2mmhg; it is best to be 1mmhg. Usually, the ultimate vacuum of chosen pumps will be a half to one order of magnitude higher than the working vacuum of vacuum device.

2,Correctly select vacuum pump’s working points. Each pump has a certain working pressure range, such as: working pressure range of 2BV series water ring vacuum pump is 760mmHg~25mmHg (absolute pressure); in such a wide range of pressure, pumping speed of pump changes with intensity of pressure (changes in detail refer to the pump performance curve); the stable working pressure range is 760~60mmHg. Thus, the pump operating point should be selected within the range, and not let it work for a long time in 25 ~ 30mmhg.

3,The vacuum pump should be able to discharge all the gas generated in the process of vacuum equipment under its working intensity of pressure.

4,Correctly combine vacuum pumps. The vacuum pump has a selective pumping gas, therefore, sometimes using a pump cannot meet the pumping requirements, need several pump combination, complement each other in order to meet the pumping requirements. Such as titanium sublimation pump has a high pumping speed of hydrogen, but not pumping helium, however the three pole sputtering ion pump, (or ambipolar asymmetric cathode sputtering ion pump) has a certain pumping speed on argon; if combine the two kinds of pumps together, they will make a vacuum device to get a better vacuum degree. In addition, some of the vacuum pumps can’t work under atmospheric pressure, they need to pre-vacuum; some of the vacuum pumps’ outlet pressure is below atmospheric pressure, they need backing pump; therefore, pump combination is needed.

5,Requirements of vacuum equipment for oil pollution. If the equipment demands oil free, they should select a variety of non - oil pump, such as: water ring pump, molecular sieve adsorption pump, sputter ion pump, cryogenic pumps etc. If the requirement is not strict, a pump with oil can be chosen, plus on a number of oil pollution prevention measures, such as adding cold trap, baffled, block the oil wells, etc., they also can achieve clean vacuum requirements.

6,Learn composition of gas to be pumped, whether gas contains condensable vapor, dust particles and corrosion. When choosing vacuum pump, it needs to know the gas composition, and the corresponding pump should be chosen according to the pumped gas. If the gas contains steam, particles and corrosive gases, it should consider to install auxiliary equipment in the pump inlet pipe, such as condensers and dust collectors.

7,Impact of oil vapor discharged from the vacuum pump on the environment. If the environment does not allow pollution, you can choose a non-oil vacuum pump, or discharge the oil vapor to the outside.

8,Whether vibration, which is generated when vacuum pump works, impact the process and environment. If the process is not allowed, it should choose pumps without vibration or take anti-vibration measures.

9,Vacuum pump price, operation and maintenance costs.

 

Selection of water ring vacuum pump

Selection of water ring vacuum pump
The type of pump mainly depends on the amount of gas, vacuum or exhaust pressure required by the work.

Pump work, you need to pay attention to the following two aspects:

  • The pump should work in the effective region as much as possible, namely within the zone of the critical vacuum or critical exhaust pressure.
  • It should avoid to work under conditions of near maximum vacuum or maximum exhaust pressure. If operate within this region, not only efficiency is very low, but also the work is not stable, easy to produce vibration and noise. For vacuum pump with high vacuum, if operate in this region, cavitation often happens; a clear sign of this phenomenon is the pump noise and vibration. Cavitation will cause damage to the pump body, impeller and other parts, and then cause the pump cannot work.

According to the above principles, when vacuum or gas pressure needed by a pump is not high, it is preferential to choose in the single-stage pump. If vacuum or exhaust pressure is high, single-stage pumps are often unable to meet, or pump under high vacuum still large capacity, which requires the performance curves at higher vacuum degree relatively flat, the use of two stage pump. If the vacuum degree is above -710mmHg, water ring- air pump or water ring - Roots vacuum units can be chosen as the pumping vacuum device.

Choose vacuum pumps according to the required air amount of the system

After the initial selection of the pump type, model of the vacuum pump should be chosen according to the required air amount of the system.About calculation of vacuum pump pumping speed and time, please refer to the vacuum calculation formula in our website Formula of vacuum.


To various types of water ring vacuum pumps and compressors, we have collected their own characteristics as follows, in order to facilitate user selection

 

Code
Main features
Ultimate vacuum mmHg
mmHg
Working vacuum degree mmHg
mmHg
Suction speed range
m3/min
Sealing form
SK
Domestic designed single-stage water ring vacuum pump, simple structure and easy maintenance. At present, the low water ring vacuum pump will gradually be replaced by2BV2BEseries products。
-700
-300~-650
0.15~120
Packing/
Mechanical seal
2SK
Domestic designed two-stage water ring vacuum pump, equivalent to two SK water ring pumps used in series, featured with high vacuum and faster pumping speed under higher vacuum by comparing with single-stage water ring vacuum pump. The current low-end water ring vacuum pump will gradually be replaced by2BV2BEseries products.
-735
-300~-700
1.5~30
Packing/
Mechanical seal
Adopt SIEMENS advanced technology, device and pump are coaxial, with compact structure, high efficiency and vacuum and stable performance, will gradually replace the SK and 2SK series water ring vacuum pumps at0.4~6m3/minpumping speed.
-735
-300~-700
0.45~8.33
Mechanical seal
Adopt SIEMENS advanced technology, with high efficiency and vacuum and stable performance, will gradually replace the SK and 2SK series water ring vacuum pumps at6~120m3/minpumping speed.
-735
-640
-300~-700
-300~-600
5~120
Packing/
Mechanical seal
Adopt SIEMENS advanced technology, with high efficiency and vacuum and stable performance, will gradually replace the SK and 2SK series water ring vacuum pumps at80~600m3/min pumping speed.
-610

0~-600
80~600
Packing/
Mechanical seal
SZ
Adopt 1950s’ Soviet Union technology with low efficiency and large energy consumption; this technology had been eliminated in early 1980s, mainly used by the old users.
-640~-700
-300~-650
1.5~27
Packing
SZB
Adopt 1950s’ Soviet Union technology with low efficiency and large energy consumption; this technology had been eliminated in early 1980s, mainly used for water pump drawing water, has been replaced by SK series water ring pumps.
-600
-300~-550
0.33~0.66
Packing

 

The water temperature has bigger impact on the water ring vacuum pump, whose performance curves are measured in 15℃ water temperature conditions, so in the practical choice of water ring vacuum pump, its pumping speed should be corrected.

Modification values of the actual pumping speed of the water ring pump can be calculated according to the Qt=Q15K,K=(P1-Pt)/(P1-P15)where:
Qt-air volume when water temperature is t℃m3/min Q15-air volume when water temperature is 15℃ m3/min
P1-water ring pump suction pressure, inmmHg Pt-saturated steam pressure when water temperature is t℃, in mmHg
P15-saturated steam pressure when water temperature is 15℃, in mmHg K-volume correction coefficient

The K value of water ring vacuum pumps under various temperature and pumping pressure can refer to the following table.

 

 

 

water temperature
Suction pressure mmHg
25
30
35
40
50
60
80
100
120
150
200
250
300
400
500
600
760
0
1.685 1.486 1.376 1.307 1.225 1.177 1.124 1.096 1.078 1.061 1.045 1.035 1.029 1.022 1.017 1.014 1.011
2
1.627 1.445 1.345 1.281 1.206 1.162 1.114 1.088 1.071 1.056 1.041 1.032 1.027 1.02 1.016 1.013 1.01
4
1.561 1.398 1.308 1.252 1.184 1.145 1.102 1.079 1.064 1.05 1.037 1.029 1.024 1.018 1.014 1.012 1.009
6
1.487 1.345 1.268 1.218 1.16 1.126 1.088 1.068 1.055 1.043 1.032 1.025 1.021 1.015 1.012 1.01 1.008
8
1.403 1.286 1.221 1.181 1.132 1.104 1.073 1.056 1.046 1.036 1.026 1.021 1.017 1.013 1.01 1.008 1.007
10
1.308 1.219 1.169 1.138 1.101 1.08 1.056 1.043 1.035 1.027 1.02 1.016 1.013 1.01 1.008 1.006 1.005
12
1.201 1.143 1.111 1.09 1.066 1.052 1.037 1.028 1.023 1.018 1.013 1.01 1.009 1.006 1.005 1.004 1.003
14
1.081 1.057 1.045 1.036 1.027 1.021 1.015 1.011 1.009 1.007 1.005 1.004 1.003 1.003 1.002 1.002 1.001
16
0.946 0.962 0.97 0.976 0.982 0.986 0.99 0.992 0.994 0.995 0.996 0.997 0.998 0.998 0.999 0.999 0.999
18
0.795 0.855 0.888 0.908 0.933 0.947 0.963 0.971 0.977 0.982 0.987 0.989 0.991 0.994 0.995 0.996 0.997
20
0.627 0.735 0.795 0.833 0.878 0.904 0.932 0.948 0.958 0.967 0.976 0.981 0.984 0.988 0.991 0.992 0.994
21
0.536 0.671 0.745 0.792 0.848 0.88 0.916 0.935 0.947 0.959 0.97 0.976 0.98 0.985 0.988 0.99 0.992
22
0.439 0.602 0.692 0.748 0.816 0.855 0.898 0.922 0.936 0.95 0.963 0.971 0.976 0.982 0.986 0.988 0.991
23
0.337 0.53 0.636 0.703 0.783 0.829 0.88 0.907 0.925 0.941 0.957 0.966 0.972 0.979 0.983 0.986 0.989
24
0.23 0.454 0.577 0.655 0.747 0.801 0.86 0.892 0.912 0.932 0.95 0.96 0.967 0.976 0.981 0.984 0.987
25
0.117 0.374 0.515 0.604 0.71 0.772 0.84 0.876 0.899 0.921 0.942 0.955 0.962 0.972 0.978 0.982 0.986
26
0 0.289 0.449 0.55 0.671 0.741 0.818 0.86 0.886 0.911 0.935 0.948 0.957 0.968 0.975 0.979 0.984
27
0.2 0.38 0.494 0.63 0.708 0.795 0.842 0.872 0.9 0.926 0.942 0.952 0.964 0.972 0.977 0.982
28
0.106 0.308 0.435 0.587 0.674 0.771 0.824 0.857 0.888 0.918 0.935 0.946 0.96 0.968 0.974 0.979
29
0.008 0.231 0.372 0.541 0.638 0.746 0.804 0.841 0.876 0.909 0.928 0.941 0.956 0.965 0.971 0.977
30
0.151 0.307 0.493 0.601 0.719 0.784 0.824 0.863 0.899 0.921 0.934 0.951 0.961 0.968 0.975
31
0.066 0.238 0.443 0.561 0.692 0.762 0.807 0.849 0.889 0.913 0.928 0.946 0.957 0.965 0.972
32
0.166 0.39 0.519 0.662 0.74 0.788 0.835 0.879 0.904 0.921 0.941 0.953 0.961 0.97
33
0.089 0.334 0.475 0.631 0.716 0.769 0.819 0.868 0.896 0.914 0.936 0.949 0.958 0.967
34
0.01 0.276 0.429 0.599 0.691 0.749 0.804 0.856 0.886 0.906 0.93 0.945 0.954 0.964
35
0.215 0.381 0.565 0.665 0.727 0.787 0.844 0.877 0.898 0.925 0.94 0.95 0.961
36
0.15 0.33 0.53 0.637 0.705 0.77 0.831 0.867 0.89 0.918 0.935 0.946 0.958
38
0.012 0.221 0.453 0.579 0.657 0.732 0.804 0.845 0.872 0.905 0.925 0.937 0.951
40
0.102 0.369 0.514 0.605 0.691 0.774 0.821 0.852 0.891 0.913 0.928 0.943
42
0.277 0.443 0.547 0.646 0.74 0.795 0.831 0.875 0.9 0.917 0.935
45
0.122 0.324 0.45 0.57 0.685 0.751 0.795 0.848 0.879 0.9 0.921
50
0.086 0.257 0.419 0.574 0.664 0.723 0.794 0.836 0.864 0.893
55
0.018 0.233 0.438 0.556 0.634 0.728 0.784 0.821 0.859
60
0.004 0.27 0.424 0.524 0.647 0.72 0.767 0.817
70
-0.18 0.068 0.23 0.429 0.546 0.624 0.704
80
0.115 0.297 0.417 0.542
100
0