Rotary blower Working principles and classification

　　Under design conditions, a fan with an air pressure ranging from 30 kPa to 200 kPa or a compression ratio of e = 1.3–3 is referred to as a rotary blower. Rotary blowers are commonly used as vacuum pumps and for pneumatic conveying systems. Depending on their specific functions, rotary blowers find extensive applications in numerous environments across both industrial production and daily life. Next, the editors of Xianji.com will provide a detailed introduction to the working principle, classification, features, installation precautions, usage guidelines, and maintenance tips for rotary blowers.

　　The working principle of a conventional rotary blower

　　1. Roots rotary blower

　　The Roots rotary blower is a fixed-volume fan whose air delivery is directly proportional to its rotational speed. With each rotation of the three-lobe impeller, air is drawn in and discharged three times by two impellers. Compared to a two-lobe impeller, this design features reduced gas pulsation, smaller load fluctuations, higher mechanical strength, lower noise levels, and reduced vibration.

　　Since the impellers rotate at a constant speed in opposite directions, a certain volume of gas is enclosed between the housing and the impellers and conveyed from the suction side to the discharge side. Each impeller is always kept in the correct phase by synchronizing gears and never comes into contact with the other. As a result, these impellers can operate at high speeds without requiring internal lubrication, feature a simple structure, ensure stable operation, deliver consistent performance, and are suitable for a wide range of applications, making them widely used across various industries.

　　2. Centrifugal rotary blower

　　As the motor rotates and drives the fan impeller to spin, the gas between the blades inside the impeller also begins to rotate. Under the action of centrifugal force, this gas is flung outward. As the gas flow velocity increases, its kinetic energy is converted into static pressure energy during the flow process. Subsequently, as the fluid is pressurized, the static pressure energy is once again transformed into kinetic energy. The gas is discharged through the exhaust port, creating a certain degree of negative pressure in the middle of the impeller. Because the inlet is under negative pressure, external air is immediately drawn in by atmospheric pressure to compensate for the loss. With the continuous rotation of the impeller, gas is constantly expelled and replenished, thereby achieving the purpose of sustained airflow.

　　3. Rotary lobe blower

　　Rotation Rotary blower The eccentric rotor in the cylinder operates with eccentricity, causing volume changes between the four vanes in the rotor slots to draw in, compress, and discharge air. During operation, the pressure differential generated by the rotary blower automatically delivers lubricating oil to the oil-drip nozzles, where it is dripped into the cylinder to reduce friction and noise while also preventing gas backflow into the cylinder.

　　Precautions for Using a Blower

　　1. The blower’s pressure must not exceed the pressure rating specified on the nameplate. Operating under overload conditions can damage both the fan and the motor, and may even lead to serious safety incidents.

　　2. During operation, the bearing temperature rise shall not exceed 75°C, and the lubricating oil temperature rise shall not exceed 45°C. When the oil temperature tends to be high during summer, it is recommended to use Shell 220# pressure-resistant lubricating oil.

　　3. During operation, pay attention to the fan’s performance. If any abnormalities are detected, immediately stop the machine for inspection and monitor the readings on the power meter. At the same time, regularly check the bearing temperature, lubricant oil temperature, and lubricant oil level, and keep detailed records.

　　5. If the safety valve frequently or continuously opens during operation, it should be immediately stopped to check whether the system is overpressurized. Resume trial operation only after the issue has been resolved.

　　6. When it is necessary to adjust the system flow, reducing the valve opening is not permitted. The flow rate of a Roots blower can be adjusted by diverting the flow or by varying its speed within the allowable range.

　　7. When using products with a water-cooling structure, please ensure that the water passages remain unobstructed. If the product is not in use, drain all cooling water from the components and dry them thoroughly.

　　8. When the oil gauge is severely contaminated, it should be cleaned or replaced promptly to ensure clear visibility of the oil level and to maintain proper lubrication of the fan.

　　Key points for blower maintenance

　　1. Before entering the fan, remove any hard objects, dust bag powder particles, fibers, and water droplets. You may use a dust collection bag for this purpose. If a filter is installed in the duct, to avoid pressure loss, use a filter with a large surface area and regularly clean the filter to remove accumulated contaminants.

　　2. Regularly clean the inside and outside of the fan, removing dust from the surface. If a large amount of dust accumulates, the cooling performance will deteriorate, potentially leading to increased temperature, reduced airflow, and increased vibration, which may cause malfunctions.

　　3. Bearings, oil seals, and mufflers are consumables with a limited service life and therefore need to be replaced periodically. Meanwhile, blades, housings, metal meshes, and other components also need to be replaced regularly depending on the operating environment.