The Advantages and Disadvantages of the Roots Vacuum Pump

The roots vacuum pump is a type of rotary vacuum pump. Its structure has evolved from the roots blower. It first appeared in 1944 in Germany, designed to handle pressures between 10 and 1000 Pa with high pumping speeds, used as a mechanical booster pump for vacuum smelting systems.

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Depending on the working pressure range, roots vacuum pumps can be divided into low atmospheric vacuum roots pumps, mechanical booster pumps, and high vacuum multistage roots pumps. The most commonly used is the roots pump. Compared to other mechanical pump types, roots pumps offer several features:

Roots pumps are known for their quick start-up, low power consumption, low maintenance cost, high pumping speed, and efficiency. They can handle gases with small amounts of water vapor and dust without being affected. In the 100 to 1,000 Pa pressure range, they can quickly remove suddenly released gases. This pressure range lies between mechanical vacuum pumps and oil-sealed diffusion pumps. Therefore, roots vacuum pumps are often used in series with these two types of pumps to enhance the swept volume in the middle pressure range, acting as mechanical booster pumps.

Additionally, roots vacuum pumps run smoothly with low noise, minimal vibration, and a high ultimate vacuum. The pump's driving part uses a reliable anti-backlash structure, allowing it to work long-term under high-pressure differences. With a fast start-up time, it can quickly achieve the vacuum limit. The absence of sliding parts and oil lubrication in the pump cavity prevents oil vapor contamination of the system. For safety, some models like the ZJ and ZJP come with overflow valves for automatic protection. The compact structure of the roots vacuum pump requires little space, and with three vent options available - left, right, or down - installation is easy.

However, the roots vacuum pump has some drawbacks. While energy consumption is relatively low, noise and vibration are higher. It demands higher verification standards and requires isolation processing.

Roots vacuum pumps are widely used in vacuum metallurgy for refining, degassing, and rolling, as well as in the chemical, food, and pharmaceutical industries for vacuum distillation, vacuum concentration, and vacuum drying.

Pneumatic conveying systems use the Roots blower as a gas source. They can transport powdery, granular, and fibrous materials such as phosphate rock, coal powder, cement, carbon black, polyethylene, polypropylene, cotton, and small pieces of materials like coal and rock.

Advantages

Pneumatic conveying systems with roots blowers have several advantages:

(1) They transport materials in a closed pipeline, preventing dust pollution and protecting materials from environmental contaminants and moisture, ensuring the quality of the transported materials.

(2) The transmission line is easy to arrange, requiring minimal floor space and allowing for full space utilization.

(3) Various production processes like cooling, heating, and drying can be completed during material transportation.

(4) With few mechanical transmission parts and a simple structure, operation and management are convenient, and maintenance costs are low.

(5) They allow for quantitative transportation, aiding production scheduling and management.

(6) They can transport materials over long distances.

(7) They can transport chemically unstable materials with inert gas.

Disadvantages

Despite their advantages, pneumatic conveying systems have some disadvantages:

(1) High power consumption.

(2) Components in the conveying pipeline can wear out easily due to contact with airflow and materials, especially when transporting abrasive materials.

(3) Certain materials are not suitable for pneumatic conveying:

Brittle materials can degrade due to crushing. Viscous materials or those that absorb moisture easily can agglomerate and block the system. Grinding materials can cause line damage. Oxidizable materials require inert gas for transportation. Materials larger than 50mm with high density are difficult to transport with this system.

Is it economical to use pneumatic conveying?

Although pneumatic conveying has some disadvantages, the total maintenance and operating costs per ton are lower than other transport methods. Shortening loading and unloading times can enhance the utilization rate of vehicles and vessels, offsetting the higher power costs. When transporting materials like flour, granulated sugar, drugs, or other foods, special hygienic treatments are needed for other methods, but not for pneumatic conveying, making it a cost-effective option overall.