1-Stage vs 2-Stage Vacuum Pumps: Understanding the Difference for Optimal Performance

 

1-Stage Vacuum Pumps

Operation of 1-Stage Vacuum Pumps

1-stage vacuum pumps employ a single-rotor design, where a rotating impeller with vanes or blades compresses the gas within a cylindrical chamber. The compression process involves the following steps:

1. Intake: As the impeller rotates, it creates a low-pressure area at the pump's inlet. Atmospheric pressure forces gas into the pump through the inlet valve.
2. Compression: The vanes or blades on the impeller trap the incoming gas and compress it as they rotate. The gas is forced into the discharge chamber.
3. Discharge: The compressed gas is expelled from the pump through the discharge valve, which opens when the pressure in the discharge chamber exceeds atmospheric pressure.

Pressure Range Capabilities

1-stage vacuum pumps typically achieve pressure ranges of 10^-2 to 10^-5 Torr (13.3 to 133 mPa). They are suitable for applications requiring moderate vacuum levels, such as:

• Laboratory vacuum ovens and desiccators
• Freeze drying
• Vacuum filtration
• Gas sampling
• Automotive testing

2-Stage Vacuum Pumps

2-stage vacuum pumps are designed to achieve deeper pressure levels compared to single-stage pumps. They employ a dual-rotor mechanism, where the first stage (low-vacuum stage) takes in process gas and transfers it to the second stage (high-vacuum stage). This allows for improved vacuum performance and deeper pressure levels.

Advantages of 2-Stage Vacuum Pumps:

• Dual-Rotor Design: The 2-stage design enables efficient compression of process gas, resulting in deeper vacuum levels.
• Improved Vacuum Performance: The dual-stage configuration enhances the pump's ability to remove gas molecules from a chamber, creating a more evacuated environment.
• Deeper Pressure Levels: 2-stage vacuum pumps can achieve deeper pressure levels than single-stage pumps, making them suitable for applications requiring high vacuum conditions.
• Industrial Applications: 2-stage vacuum pumps are widely used in industrial settings where deep vacuum levels are crucial, such as in the semiconductor, aerospace, and research industries.

Applications of 2-Stage Vacuum Pumps:

2-stage vacuum pumps find application in various industries, including:

• Semiconductor manufacturing: Achieving vacuum levels necessary for deposition and etching processes.
• Aerospace: Creating high vacuum environments for testing and simulating space conditions.
• Research and development: Facilitating experiments and investigations requiring ultra-high vacuum conditions.
• Vacuum degassing: Removing gases from liquids or materials through vacuum extraction.
• Freeze drying: Creating low-pressure environments for preserving and dehydrating products.

Operating Principle of Diaphragm Vacuum Pumps

Diaphragm vacuum pumps are single or multi-stage dry compressing vacuum pumps. The circumference of a diaphragm is tensioned between a pump head and the casing wall. It is moved in an oscillating way by means of a connecting rod and an eccentric. The pumping or compression chamber, the volume of which increases and decreases periodically, effects the pumping action.

The valves are arranged in such a way that during the phase where the volume of the pumping chamber increases it is open to the intake line. During compression, the pumping chamber is linked to the exhaust line. The diaphragm provides a hermetic seal between the gear chamber and the pumping chamber so that it remains free of oil and lubricants (dry compressing vacuum pump). Diaphragm and valves are the only components in contact with the medium which is to be pumped.

When coating the diaphragm with PTFE (Teflon) and when manufacturing the inlet and exhaust valves of a highly fluorinated elastomer, it is then possible to pump aggressive vapors and gases. It is thus well suited for vacuum applications in the chemistry lab.

The performance range of high-quality diaphragm pumps is around an ultimate vacuum of 75 to 1 mbar as well as a pumping speed of 138 l/m maximum. In addition, dry vacuum ensures a clean working environment. An aspect that is of fundamental importance in everyday laboratory and institute work.

Vacuum Control Methods

Two-Step or On/Off Vacuum Control: High and Low Setpoints, Unsupervised Operation

Two-step or on/off vacuum control is a simple and effective method for controlling the vacuum level in a system. This method uses two setpoints, a high setpoint and a low setpoint. When the vacuum level in the system reaches the high setpoint, the vacuum pump is turned off. When the vacuum level drops to the low setpoint, the vacuum pump is turned on again.

This method of vacuum control is often used in applications where the vacuum level does not need to be precisely controlled. It is also a good choice for applications where the system can be left to run unsupervised. Once the high and low setpoints have been set, the system will automatically maintain the vacuum level within the desired range.

One advantage of two-step vacuum control is that it is relatively simple to implement. It does not require any complex control algorithms or expensive equipment. Another advantage is that it is a very reliable method of vacuum control. The system will continue to operate as long as the vacuum pump is functioning properly.

However, there are also some disadvantages to two-step vacuum control. One disadvantage is that it can be difficult to achieve precise vacuum control with this method. The vacuum level will fluctuate between the high and low setpoints, and it may not be possible to maintain a constant vacuum level. Another disadvantage is that this method can be inefficient. The vacuum pump will be turned on and off frequently, which can waste energy.

Overall, two-step vacuum control is a simple and reliable method for controlling the vacuum level in a system. It is a good choice for applications where the vacuum level does not need to be precisely controlled and where the system can be left to run unsupervised.

Choosing the Right Vacuum Pump

When selecting a vacuum pump, it's crucial to consider the following factors:

Pressure Requirements:

• Determine the level of vacuum (pressure) required for your application.
• Laboratory/Filtration Vacuum pumps: Vacuum and pressure capabilities for general laboratory use.
• Rough Vacuum pumps: Vacuum for applications below 10–3 Torr.
• High Vacuum pumps: Vacuum higher than 10–3 Torr.

Free Air Capacity:

• The larger the free air capacity, the faster the pump will evacuate the chamber.

Lubrication:

• Lubricated pumps: Provide higher vacuum levels but require maintenance.
• Non-lubricated pumps: Lower vacuum levels but are maintenance-free.

Additional Considerations:

• Pump Application: Determine the specific purpose of the pump.
• Noise Levels: Consider the noise level of the pump, especially in laboratory settings.
• Specific Requirements: Consider factors such as pumping speed, chemical resistance, electronic control, media compatibility, and special requirements for solvent recovery, efficiency, or explosion protection.

Selection Process:

1. Identify your application requirements and pressure range.
2. Determine the appropriate free air capacity for your application.
3. Consider the lubrication requirements and noise levels.
4. Address any specific requirements for your application.
5. Consult a pressure-range chart or use an online pump finder tool to identify suitable pump options.

Conclusion

When selecting a vacuum pump, understanding the differences between 1-stage and 2-stage designs is crucial for optimal performance. 1-stage pumps offer a simple and cost-effective solution for moderate vacuum levels, while 2-stage pumps provide superior vacuum performance and are ideal for industrial applications requiring deeper pressure levels. By carefully considering the pressure requirements and specific needs of your application, you can make an informed decision to ensure the most efficient and effective vacuum solution.

If you are interested in this product you can browse our company website, as an industry-leading laboratory equipment manufacturer, we are committed to providing the most advanced and high-quality laboratory equipment solutions. Whether you are engaged in scientific research, teaching or industrial production, our products will meet your needs for accurate and reliable laboratory equipment.