Equipment Rotational Speed:
The discharge capacity of a screw air compressor is directly proportional to its rotational speed, which often fluctuates with changes in power grid voltage and frequency. A drop in voltage or frequency causes the rotational speed to decrease, thereby reducing the compressor's discharge capacity.
Suction Conditions:
Screw air compressors are positive-displacement machines with a fixed suction volume. If the intake temperature rises or excessive resistance in the suction piping causes the intake pressure to drop, gas density decreases, leading to a corresponding reduction in discharge capacity.
Gas Leakage:
During operation, there is no physical contact between the rotors themselves or between the rotors and the casing; specific clearances are maintained, which inevitably leads to gas leakage. Discharge capacity decreases when high-pressure gas leaks back through these clearances into the suction piping or into rotor grooves currently undergoing the suction process. To minimize leakage, sealing teeth are machined onto the tips of the driven rotor, sealing grooves are cut into the roots of the driving rotor, and annular or linear sealing teeth are machined onto the end faces. Wear on these sealing surfaces increases leakage; therefore, these factors must be considered during routine maintenance.
Cooling Effect:
Gas temperature rises during the compression process, causing a corresponding increase in the temperature of the rotors and casing. Consequently, during the suction phase, the intake gas expands due to heating from the rotors and casing, resulting in a reduced intake volume. Some screw air compressors employ oil cooling for the rotors and water cooling for the casing to lower operating temperatures. If cooling is ineffective, temperatures rise, leading to a reduction in the compressor's discharge capacity.
