4 Reasons for Changes in the Exhaust Volume of Screw Compressors

Screw compressors are widely used in industrial applications for their efficiency in compressing gases. However, the actual exhaust volume can sometimes differ from the theoretical exhaust volume. While the theoretical exhaust volume is determined by factors such as the inter-tooth volume, the number of teeth, and the rotation speed, practical factors often cause deviations. Here are four key reasons that contribute to changes in the actual exhaust volume of screw compressors:

1) Leakage

Leakage is one of the primary factors that reduce the exhaust volume of screw compressors. During operation, there is a gap between the rotors and between the rotors and the casing, which is necessary for their movement. However, this gap can lead to gas leakage. When gas with increased pressure leaks into the suction pipe or the meshing groove being inhaled, the amount of gas exhausted is reduced.

• Prevention: To minimize leakage, sealing teeth are added to the driven rotor, and sealing grooves are created on the root of the active rotor. Additionally, ring-shaped or strip-shaped sealing teeth are often processed on the end face. However, when these sealing components wear down over time, the leakage increases, and consequently, the exhaust volume decreases.

2) Inhalation State

Screw compressors are positive displacement compressors, meaning the suction volume remains constant under normal conditions. However, changes in the suction conditions can affect the actual exhaust volume.

• Temperature: When the suction temperature rises, or if there is excessive resistance in the suction line, the suction pressure drops. This leads to a decrease in the density of the gas. Since the mass flow rate of the gas is proportional to its density, a reduction in gas density causes a corresponding decrease in the mass exhaust volume.

3) Cooling Effect

During the compression process, the temperature of the gas, rotor, and casing increases. If the compressor is not adequately cooled, this temperature rise can reduce the exhaust volume. The gas is heated by the rotor and casing, causing it to expand and reduce the suction volume.

• Cooling Methods: Some screw compressors are equipped with oil cooling for the rotors and water cooling for the casing to maintain optimal temperatures. However, when the cooling effect is insufficient, the temperature rises, and the exhaust volume decreases. Proper cooling is essential for maintaining the desired performance and efficiency of the compressor.

4) Speed

The speed of the compressor is directly proportional to its exhaust volume. The speed of screw compressors can vary depending on factors like the voltage and frequency of the power grid. A decrease in voltage or frequency can lead to a reduction in the speed of the motor, which in turn reduces the exhaust volume.

• Impact of Speed: If the compressor operates at a lower speed, it will not compress as much gas within the same time frame, resulting in a lower exhaust volume. This can happen in situations where the power supply is unstable, or the motor is experiencing issues with voltage or frequency.

Conclusion

Several factors contribute to the variation in the actual exhaust volume of screw compressors. Leakage, changes in suction conditions, cooling inefficiency, and speed fluctuations all play a role in reducing the theoretical exhaust volume. To optimize performance, it is essential to regularly maintain sealing components, monitor suction and cooling conditions, and ensure the compressor operates at its intended speed. By addressing these factors, you can maintain the efficiency and reliability of screw compressors in your applications.

The Wide Application of Air Compressors in the Construction

There are roughly three levels of water removal in the exhaust of air compressors: