Answer: (1) Efficiency. The efficiency of excellent direct drive can reach 98%~99%, and the efficiency of excellent belt drive design can also reach 99% under normal working conditions. The difference between the two does not depend on the choice of transmission mode, but on the design and manufacturing level of the manufacturer.
(2) No-load energy consumption.
1) For direct drive mode, the no-load pressure should generally be maintained above 2.5 bar(1bar=105Pa), and some even reach 4 bar to ensure the lubrication of the speed change gearbox.
2) For belt drive mode, theoretically the no-load pressure can be zero, because the oil sucked into the rotor is enough to lubricate the rotor and bearings. Generally, for safety reasons, the pressure is maintained at around 0.5 bar.
(3) For direct drive mode, the first victim in the event of oil loss will be the speed change gearbox, and there is no such safety problem in the belt drive system.
(4) Damage to the motor or rotor bearing. For direct-drive air compressors, when the motor or rotor bearing is damaged, it often affects the connected important components and causes direct and indirect damage. This does not happen with belt-driven air compressors.
(5) Changes in the pressure of installed air compressors. Sometimes, due to changes in the user's production process conditions, the design pressure of the original air compressor may be too high or too low, and it is hoped that it can be changed. However, for gear-driven air compressors, this work will be very difficult and expensive, while for belt-driven air compressors, it is a piece of cake and only requires replacing the pulley.
(6) Install new bearings. When the rotor bearing needs to be replaced, for direct-drive air compressors, the gearbox and gearbox main shaft bearings need to be overhauled at the same time, which is expensive. For belt-driven air compressors, this problem does not exist.
(7) Equipment maintenance. Any screw air compressor uses an annular shaft seal, which needs to be replaced after a certain lifespan. For direct-drive air compressors, the motor and coupling must be separated before the shaft seal can be approached, making this work time-consuming and labor-intensive, thereby increasing maintenance costs. For belt-driven air compressors, you only need to remove the pulley first, which is much easier. However, belt-driven air compressors are prone to belt wear during operation, and the belt needs to be replaced from time to time, which increases the workload of maintenance and inspection.
(8) Structural noise. For direct-drive air compressors, due to the rigid connection between the motor and the rotor, the vibration of the compression chamber rotor will be transmitted to the gearbox and motor bearings, which not only increases the wear of the motor bearings, but also increases the machine noise.
