Screw Compressor Rotors Gap Adjustment Method & Steps ~Reverse Guidance

Writer： admin Time：2022-11-02 00:00:00 Browse：586℃

The screw compressor airend has two rotors. They are actually a pair of intermeshing helical gears. Therefore, we treat the synchronous gear and the screw rotors as an integral part. And analayze it basing on the theory of cogging gear meshing in gear transmission. Firstly, change the initial phase angle between the male and female rotors. Thereby, it can adjust the ratio of the meshing gap of the screw compressor rotors.

How to adjust the rotors gap of screw compressor airend? 1. Gap design

When the screw compressor is working, the motor drives the rotors to rotate at high speed. The two end faces of the compressor casing are stationary parts. There must be a certain end face gap between them. As compressor power increases, the end face clearance that needs to be adjusted will also increase. So we need to adjust the exhaust end face gap. If adjustment is too much, it will reduce the compressor displacement. On the contrary, it is easy to cause friction between the rotors and the exhaust end face. Therefore, the gap size is usually determined according to the actual engineering experience.

Generally, the gap is determined according to various factors of the compressor. It’s such as the power, operating conditions, the material of rotor and cylinder, etc. As long as the gap vary within a certain range, it can guarantee the normal operation of screw compressor.

2. Airend rotor operating characteristics

The screw compressor rotor tooth surface is mainly used for compressing air. The male and female rotors form many tooth slots. They mesh with each other to form several working chambers. The two rotors don’t touch directly during the working process. The power transmission between the two rotors is carried out through the synchronous gear. Firstly, the rotors tooth profile needs to meet the conjugate meshing. It is also necessary to have a small leakage triangle. In addition, there must be a larger area utilization factor and a higher volumetric efficiency.

The most important thing for screw compressors is the rotor face profile. The quality of the rotor profile determines the performance of the screw compressor.

3. Theoretical basis

The meshing clearance of the screw compressor is controlled by the synchronous gear. The 2 gears have the same pitch circle as their corresponding rotors. Because the driving gear and the male rotor are connected by a key, they can be regarded as an integral gear. However, the driven main ring gear and the backlash gear ring are all sleeved on the hub. After the hub and the female rotor are connected by a key, the two ring gears are still adjustable.

When the center distance is constant, the meshing backlash of the gear pair is determined by the characteristic parameters of the gear itself. Likewise, for rotor meshing, the total screw-rotor meshing gap is also constant. Of course, the premise is to ignore the slight influence of bearing clearance on the intermediate distance.

During the maintenance process, adjust the meshing clearance of the screw compressor. Keep the female rotor still. Then fine-tune the driven gear ring. That is, change the position of the positioning pin between the driven gear ring and the upper hub of the female screw rotor. So make slight changes to the initial phase angle of the male and female screw rotors meshing.

4. Specific adjustment steps

First, loosen the fastening bolts and locating pins between the driven gear ring and the hub. Make it flexible. Then use the crank to make the male and female rotors in close contact. In this way, it can accurately measure the total gap of the meshing of two rotors. So calculate the difference between the desired gap value and the total gap. Afterwards, clamp the feeler gauge with the same or similar gap difference between the chasing surface and the chasing surface of the female and male rotors by cranking. When adjusting, you can hit the screw on the synchronous gear with a copper rod. Stop until the feeler gauge is pressed down.

Rotate the driven gear ring to just mesh with the driving gear. NOTE: If necessary, place the gear backlash completely on one side of the meshing teeth. And tighten the fastening bolts between the driven gear ring and the hub. Pull out the feeler gauge between the male and female rotors. At this time, this gap is the meshing gap between the female and male rotor tooth surfaces. But in order to be safe, you need to check one by one with a feeler gauge while turning the gear. Besides, carefully measure the meshing clearance of each part of the rotor.

The total gap between the female and male rotors of the screw compressor is relatively large. Therefore, the adjustable range of the gap ratio of the device is also large. Generally speaking, the gap ratio should be controlled between 0.8 and 1.2 wires. In fact, the screw compressor rotates at high speed. There is thermal deformation of the tooth profile and wear of the gear tooth surface. So the chasing gap tends to decrease. In addition, the non-chasing face gap tends to increase. In order to ensure the long-term reliable operation of the compressor, should increase the chasing gap during maintenance. Also, make the non-chasing surface gap smaller. Make the ratio of these two kinds of gaps between 1.0 and 1.2. This is more reasonable.

5. Summary

The adjustment of the meshing gap is the most critical step in the maintenance of the entire screw air compressor. It is directly related to the normal operation of the screw compressor. Besides, it’s a difficult job. Sometimes we need repeated adjustments to meet the requirements.

The above is different from traditional thinking. It uses reverse thinking. Firstly, give a initial phase of the rotors. Then adjust the meshing gap between the driven and driving gear ring. Finally, fasten with the tightening bolts. Under normal circumstances, this method can directly obtain the required screw compressor meshing gap. So it reduces the time to repeatedly measure the gap and adjust the driven ring gear. Effectively shorten the maintenance cycle.