Wear failure of the screw cross-section in Bizer compressor
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I recently took over a Bizerba twin-screw refrigeration compressor. After removing the rear cover, manual rotation of the shaft resulted in jamming; it was determined that the motor was burned out. After disassembly, the bearing cover at the suction end of the male rotor was worn, and the cross-section of the male rotor at the suction end was also worn. The exhaust end face is in good condition. Was it caused by bearing failure in the rotating shaft, or was it due to foreign objects getting inside which led to damage at the cross-section and wear of the cylinder block?
Judging from the 4th piece, it seems that the bearing is lacking oil, and the end cover has been corroded; rust and impurities have damaged the end cover, resulting in foreign objects that damage other components as well. Judging from the diagram, it seems to be a system for thin oil lubrication, of the type where oil and gas are mixed together and then separated. This phenomenon is mainly related to the environment in which the equipment is located; it may be caused by an excessively high level of particulates, corrosive gases in the air, or a damaged air filter. The key issue lies in the management of the equipment, as well as its proper use and maintenance. (For reference)
Personally, I think this issue with the exhaust from the positive rotor is caused by an excessively small size, and the reasons are as follows: 1. A lack of oil generally does not cause wear in this area; when there’s a lack of oil, the most noticeable effect is on the bearings. 2. If foreign objects get in, the scratches should appear directly on the male and female rotors or on the wall, not at this location. So I think it’s likely that an excessive gap in the positioning bearing of the rotor causes the rotor to shift, which in turn leads to wear at the suction end. (During operation, the exhaust pressure is higher than the suction pressure, so the rotor is pushed back; if the angular contact bearings are in good condition and the balance disc is also functioning properly, this force will be counteracted, otherwise wear will occur as shown in the diagram.)
Screw compressors are used in refrigeration systems. The cavity has scratches. You’re saying that even if the clearance of the positive rotor is large, it won’t shift to the intake end at the back. In some compressors, the motor is directly connected to the screw, with the motor located in the low-pressure chamber. In Figure 4 of the photos, the end face is the low-pressure chamber end face. Some end faces are not required to have a specific gap. What is required is probably the gap between the exhaust end face and the exhaust seat
Is the one you repaired bigger, or is the one I repaired bigger? P;P First, when analyzing a pump, it’s necessary to obtain relevant data – what were the conditions during the last maintenance session, and what is the gap in the gland? What is the axis runout? What is the gap on the back of the leaf? What is the total serial quantity of the shafts? How much is the string division amount? What was the vibration level according to the inspection records from the past month? What’s the temperature? Is everything okay? I don’t believe it. If even the bearing caps can get worn out, just imagine to what extent the wear is severe; this leads to wear on the back side of the rotor blades, and the worn material falls into the cylinder block, causing wear there as well. With the gland worn down to that extent, the temperature during inspections won’t be high: lol. Also, before taking out the male and female rotors, make sure to mark them properly. I noticed that your male rotor has 5 working surfaces, while the female rotor has 6; these need to match precisely. The male rotor has surfaces A, B, C, D, E, and the female rotor has A, B, C, D, E, F. When point A on the male rotor rotates one full circle, how many degrees does point A on the female rotor rotate? This is all predetermined – don’t mess it up
I don’t understand the issue you’re referring to regarding the angles of ABCDE and ABCDEF. Now I feel that there’s also a bottleneck in bringing it back for repair. It can’t be turned with one hand; a wrench is needed to turn it. The experienced worker said that once power is applied, just turn it manually. It’s said to be no big problem. Additionally, a 0.02 shim cannot be inserted into the exhaust end face at present. I would like to ask if what the experienced master says is correct? Will it disappear once power is applied and it moves past the checkpoint? I took a look and the gap between the male and female rotors is opaque in the two slots on the exhaust side. Is it related to the angle you mentioned? These two screws are not driven synchronously by gears.
I went to adjust it manually today. Circular runout; the position of the sticking point reaches 0.2 mm
The position without jamming is 0.05mm
The worn areas can be repaired; our company is capable of doing this, having years of mature technical expertise. ^_^