How to Choose Roots Vacuum Pump For Sale?

How to choose Roots vacuum pump correctly

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Today small make up for you to sum up how to correctly choose the roots vacuum pump, and need to pay attention to matters

1. The working pressure of roots vacuum pump shall meet the requirements of extreme vacuum and working pressure of vacuum equipment. For example, a vacuum drying process requires a working vacuum of 10mmHg, the ultimate vacuum of the selected roots vacuum pump should be at least 2mmHg, and the best can reach 1mmHg. Generally, the ultimate vacuum of the selected pump is higher than the working vacuum of vacuum equipment by half to one order of magnitude.

2. Correctly select the operating point of roots vacuum pump. Each pump has a certain range of working pressure, such as: 2BV series water ring roots vacuum pump unit working pressure range of 760mmHg~25mmHg(absolute pressure), in such a wide range of pressure, pump speed with pressure changes (refer to the pump performance curve for detailed changes), its stable working pressure range of 760~60mmHg. Therefore, the working point of the pump should be selected in this range is more appropriate, and can not let it work in 25~30mmHg for a long time.

3. Requirements of vacuum equipment for oil pollution. If the equipment strictly requires no oil, should choose a variety of pumps, such as: water ring pump, molecular sieve adsorption pump, sputtering ion pump, cryogenic pump. If the requirements are not strict, you can choose a pump, plus some anti-oil pollution measures, such as cold trap, baffle, oil trap, etc., can also meet the requirements of clean vacuum.

4, to understand the composition of the gas, gas containing condensable steam, no particle dust, no corrosion, etc. When selecting a roots vacuum pump, you need to know the gas composition and select the appropriate pump for the pumped gas. If the gas contains steam, particles, and corrosive gases, it should be considered to install auxiliary equipment, such as condenser, dust remover, etc. on the inlet pipe line of the pump.

5, roots vacuum pump in its working pressure, should be able to discharge all the gas produced in the process of vacuum equipment.

6. Correctly assemble roots vacuum pump. As a result of the roots vacuum pump has the selective pumping, therefore, sometimes chooses a kind of pump to be unable to satisfy the pumping request, needs several kinds of pumps to combine, may supplement mutually to satisfy the pumping request. For example, the titanium sublimation pump has a high pumping speed for hydrogen, but cannot pump helium, while the three-pole sputtering ion pump (or the two-pole asymmetric cathode sputtering ion pump) has a certain pumping speed for argon. In addition, some roots vacuum pump can not work under atmospheric pressure, the need for pre-vacuum; Some roots vacuum pump outlet pressure is lower than atmospheric pressure, the need for the former pump, so the pump needs to be used together.

7. Whether the vibration caused by the operation of roots vacuum pump has any influence on the process and environment. If the process does not allow, should choose no vibration of the pump or take anti-vibration measures.

8. What is the influence of oil vapor discharged by roots vacuum pump on the environment? If the environment does not allow pollution, you can choose oil-free roots vacuum pump, or the oil vapor exhaust to the outdoor.

ZJ Vacuum Roots pump picture display

ZJ Roots Vacuum Pump Technical Parameters：

Model ZJ-150 ZJ-300 ZJ-600 ZJ- Pumping speed（L/s） 150 300 600 Ultimate pressure
（Pa） 1 stage piston pump as backing pump 5×10-2 2 stage piston pump as backing pump 1×10-1 Max. allowable diff. pressure（Pa） 8×103 5×103 Motor rotary speed（RPM） Suitable motor power（kW） 2.2 4 7.5 11 Flange size Inlet（mm） 100 150 200 250 outlet（mm） 100 150 200 200 Cooling water consumption（L/h） 120 150 Allowable temperature（℃） 100 Vacuum pump oil 100# Weight(without motor)（kg） 195 250 760 860

ZJP Vacuum Roots pump picture display

ZJP Roots Vacuum Pump Technical Parameters：

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When the time comes to select a new vacuum pump or pumpset, be it for a new system or to upgrade an existing one it's important to take several key factors into account. These will determine the pump type(s) and the required pumping capacity.

Various factors affect a vacuum pump’s overall efficiency and capabilities. Each pump requires its own process conditions, has its own operating range, and offers its own sets of benefits and limitations. These characteristics depend on four factors: 

• Vacuum level and pumping speed
• Process or application impact on pump 
• Pump impact on process or application
• Cost and maintenance

Forevacuum pumps pumping speed is measured in m3h-1, and for high vacuum pumps l/s is used:  1m3h-1 = 3.6 l/s

Contact us to discuss your requirements of Roots Vacuum Pump For Sale. Our experienced sales team can help you identify the options that best suit your needs.

There are two considerations when choosing the correct pumping speed: 

• Pumpdown time before a process can start – this should be as short as possible to minimize production costs
• Process flows – here the pumping speed must be able to maintain an appropriate pressure when process gases are employed. 

Depending on the target vacuum level and pumpdown time, a variety of different vacuum pump technologies might be necessary. 

Forevacuum pumps — those operating in the rough and medium vacuum ranges. These types of pump operate by compressing gases and then exhausting to atmosphere. Applications include food packaging, heat treatment and freeze drying. 

High and ultra-high vacuum pumps — such as turbopumps and diffusion pumps — operate only in conjunction with a forevacuum pump and operate by the molecular transfer method. Applications include coating, metallurgy, and analytical applications.

Ion, non-evaporable getter pumps, and cryopumps work by trapping gases. In the case of a cryopump, this is achieved by freezing the gases. Evacuation and occasional forevacuum is needed at certain stages. Applications include R&D, high energy beam lines and space simulation. 

There are several types of forevacuum pumps

• Oil sealed rotary vane pumps 
• Scroll pumps
• Diaphragm pumps
• Screw pumps

Rotary vane technology is a popular choice for medium vacuum applications, but will exhibit oil back streaming. This can be an issue if a process is sensitive to contamination, for example precision coating. If the application demands an oil free environment, diaphragm and scroll pumps in particular would be suitable. However, both have lower pumping speeds than a rotary vane pump and the scroll can generate particles from its tip seals and is best suited to benign applications. Moreover, diaphragm pumps have a poor base pressure.

For high pumping speeds with good base pressure, the addition of roots pumps in combination with a rotary vane pump will increase pumping speed, but oil back streaming will still occur. Screw drypumps are an oil free option with high pumping speeds even without an added roots pump and can also handle difficult process applications.

There are several choices available for an additional pump for high vacuum processes: 

• Diffusion pumps
• Turbomolecular pumps 
• Entrapment pumps including cryopumps

Both diffusion pumps and turbo pumps offer similar base pressures. As with RV pumps, diffusion pumps are a source of oil contamination, but offer high pumping speeds. Turbomolecular pumps are an oil free option. However, the maximum pumping speed of the largest turbo is only around 5% that of a large diffusion pump.  

For processes requiring large throughput in the high vacuum range, similar to a diffusion pump but without the issue of oil contamination, a cryopump where gases are trapped using low temperature might be appropriate. These pumps do not require a backing pump whilst operating, but will need a forevacuum pump for regenerating - the frequency of which would be process dependent.

Making the right pump choice for effective vacuum generation requires an understanding of how pumps impact processes — and how processes impact pumps. Vacuum level needs, pumping speeds, running costs and maintenance also impact vacuum pump choice. 

Choosing the wrong pump can be expensive and potentially damaging to your operation if the pump does not perform as required. No amount of reading can make up for a quick meeting with a team who can answer all the questions even the most fastidious research raises. Reach out and let's chat.

Ensure you make the right choice, with the help of our team of leading vacuum technology experts. 

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