Direct Drive Air Compressor vs. Belt Driven Air Compressor

As an important form of energy generation, air compressors are widely used in various industrial fields, including mechanical, metallurgy, Electronic power, medicine, packaging, chemicals, food, textile, transportation and so on.

Direct drive air compressor vs. belt driven air compressor

Direct drive of air compressor refers to the motor main shaft to drive the rotor by the coupling and the gearbox speed, which is not actually a direct drive in practical sense.

Direct drive in the true sense means that the motor is directly connected with the rotor (Coaxial), which has the same speed. This situation is obviously very rare. Therefore, it is a wrong view that there is no energy loss in direct drive.

Another drive way is belt driven, which allows the rotating speed of the rotor to be changed by pulleys of different diameters.

The belt driven system discussed below referring to an automation system representing the latest technology that meets the following conditions:

• The belt intension of each running state has reached the optimized value.
• By avoiding starting tension excessively, the working life of the belt is greatly extended, meanwhile reducing the load of motor and rotor bearing.
• Always make sure the correct pulley connection.
• It is easy and fast to change the belt, and don’t need to adjust the original settings.
• The entire belt driven system operates safely and without problems.

Difference between direct gear driven and belt driven air compressor

1. Efficiency

The excellent gear driven efficiency can reach 98%-99%, and the excellent belt driven efficiency also can reach 99% under normal work. The difference between gear driven and belt driven doesn’t depend on the choice of drive method, but mainly depends on the design and manufacturing level of the manufacturer.

2. No-load energy consumption

Regarding the method of gear direct drive, no-load pressure is generally maintained above 2.5bar, some even up to 4bar to make sure that the gear box lubricate.

For the method of belt driven, theoretically, no-load pressure can be zero, because the oil sucked by the rotor is enough to lubricate the rotor and bearings. Generally for safety, the pressure is maintained at about 1.5bar. To a 160kW gear direct drive air compressor as an example, working 8000 hours per year, of which 15% (that is 1200 hours) of the time is no-load, this machine will consume 28800kwh more than a belt driven air compressor electricity costs (assuming that the no-load pressure difference between the two air compressors is 2 bar, about 15% of the energy consumption difference), in the long run, this will be not a small expense.

3. Oil loss

Experienced practical users know that gear box is the first to suffer from the situation of oil loss. The belt driven system completely doesn’t have this safety problem.

4. According to user requirements design working pressure

Usually the working pressure in user requirements is incomplete consistent with standard model of manufacturer. For example, the pressure of the user’s requirement is 10bar. But according to post-processing equipment status, difference of piping length and sealing length requires that the working pressure in air compressor is probable 11 or 11.5bar. Under this circumstance, an air compressor with 13bar rated pressure is installed and outlet pressure is set a working pressure of requirement at the same time. At this moment, displacement basically maintains constant, because the working pressure reduces finally, but the speed of the rotor doesn’t increase.

Belt driven design is on behalf of modern technology. Manufacturer just simply changes the diameter of pulley to design the working pressure fully consistent with user requirements. Therefore, users using the motor with same power will obtain more air volume. However, the gear driven is not convenient for this.

5. The pressure change of air compressor installed

Sometimes, the user hopes to change the pressure because the change of the user production processes conditions and the pressure in the original purchased probably too high or too low. That is extremely convenient for belt driven air compressor, which only needs to replace the pulley. However this work will be extremely difficult and expensive for gear driven compressor.

6. To install new bearing

When rotor bearing need to be replaced, for gear driven air compressor, gearbox and gearbox bearings need to repair, which generates a lot of expenses. However belt driven air compressor hasn’t this problem.

7. To replace shaft seals

Any air compressors use a kind of ring shaft seals, which needs to replace when it comes to a certain life. For gear driven compressor, it needs to separate motor and coupler and then close to shaft seals, which spends a lot of time and adds maintenance costs. Difference in gear air compressor, the belt driven air compressor only needs to unload the pulley, which is very convenient.

8. Damage of motor or rotor bearing

When the motor or rotor bearing of gear driven air compressor is damaged, they usually affect other important connected parts, causing direct and indirect to damage. But the belt driven air compressor doesn’t exist this situation.