Current Market Dominance and Common Issues of Screw Air Compressors

Currently, screw air compressors dominate the market. These are common mechanical devices that, over time, may develop faults. Below are several typical accident cases involving screw-type air compressors for your reference.

Mixing Lubricating Oils Leading to Carbon Buildup
Fault Phenomenon:

The factory installed 10 air compressors using the original lubricating oil provided by the manufacturer. Due to the high cost of the lubricating oil, they decided to use a substitute oil, which was also a synthetic oil. As a safety precaution, they first tested the new synthetic oil on two small-power compressors. After 1500 hours of using the new synthetic oil, the compressors triggered an electrical fault alarm. Further inspection revealed that the cause was carbon buildup due to the compressor motor running at overcurrent.

Reason Analysis:

Inspection showed no carbon buildup inside the compressor, and after about 6000 hours of normal maintenance, the compressors worked with different groups of workers.
Investigation confirmed that the maintenance staff had not thoroughly drained and cleaned the compressors, leading to a mix of different types of lubricating oils and resulting in carbon buildup.

Compressor Fault Leading to Plant Shutdown
Incident Details:

One morning at 10:11, maintenance personnel were asked to address a defect in the de-dusting compressor's drainage valve. The operating staff stopped the de-dusting compressor (the upper-level computer showed it was stopped, but it was still running at the time). Maintenance personnel opened the noise reduction cover and found that the de-dusting compressor’s cooling fan was still running. They notified the operating staff, who pressed the emergency stop button, but the staff mistakenly cut off the power supply to the electromagnetic valve. At 10:18, smoke and fire were observed coming from the cooling fan. Despite attempts to extinguish the fire, by 10:21, the control room staff found that the high-voltage transformer switch had tripped, and the high-voltage transformer protection branch zero-sequence overcurrent protection had acted. Subsequently, two air preheaters in the boiler tripped, causing the fan to trip as well.

Reason Analysis:

The de-dusting compressor’s switch had poor contact and refused to operate while it was supposed to be stopped. Incorrect operation by the maintenance staff led to a complete plant shutdown.

Untimely Maintenance Causing Main Engine Failure

Fault Phenomenon:

An air compressor in a factory experienced an electrical fault alarm and stopped. Upon opening the intake port, it was found that the compressor rotor was coated with a large amount of light-colored gel-like substance, and the compressor housing also had a significant amount of the same substance. It was confirmed that the compressor had developed carbon buildup. Maintenance records showed that the compressor had run continuously for 8000 hours without maintenance. After cleaning and servicing the compressor, it was sent back to the factory for repair. The manufacturer’s inspection revealed noticeable wear grooves on several rolling paths and rollers of the compressor’s bearings, with gaps between the main and secondary rotors smaller than the design value. Both rotors had significant wear marks. The compressor bearings were replaced, and the worn rotors were ground. The compressor was reassembled and tested successfully after reinstallation.

Reason Analysis:

The commonly used synthetic lubricating oil for air compressors has a lifespan of about 6000 hours. The oil used for 8000 hours had degraded in viscosity, impurity particles, and carbon buildup tendency, causing bearing wear and carbon buildup.

Long-Term Inactivity Leading to Equipment Failure

Fault Phenomenon:

A power plant’s pneumatic ash conveying system was equipped with four screw-type air compressors used as a gas source for transportation. Typically, three compressors run while one remains as a backup, with the backup compressor being switched regularly, every month. During a recent switch of the backup compressor to the operating state, the compressor ran for less than 2 minutes before a loud noise was heard. The compressor's operating time changed abruptly. The operator checked and found no visible oil level in the oil-gas separator. The compressor was stopped immediately, and after relieving the pressure, the oil level was still not visible. Maintenance personnel were notified and suspected that the oil-gas separator filter element was damaged, causing the lubricating oil to be drawn out. Upon inspection, it was found that the filter element had been severely deformed and had a rupture, with only a small amount of lubricating oil left in the oil-gas separator.

Reason Analysis:

The appropriate duration for the backup compressor to remain unused varies by climate conditions. In this factory, problems had previously arisen with the compressor’s filter element clogging after being idle for a month. This indicated that a one-month idle period was not suitable for this factory's compressors. Long-term inactivity led to the accumulation of oil and dirt on the oil-gas separator filter element, reducing its flow area. When the compressor was restarted, new oil adhered to the filter, further reducing the flow area, causing deformation and rupture of the filter due to the extreme pressure difference, and leading to the loss of lubricating oil.