Failure Analysis of Compressor Inlet Filter Tearing

During daily compressor operation, inlet filter fault is one of the frequent alarm triggers. This fault may occur when the ambient air contains excessive contaminants, 

such as dusty working environments or polluted industrial zones. Under such conditions, the inlet filter triggers an alarm before reaching its normal replacement cycle. 

Alarms can also be generated when the filter truly reaches the end of its service life. These two scenarios are common and easy to resolve — simply replace the inlet filter in a timely manner. 

Such failures are not complicated to handle. However, tearing of the inlet filter is a relatively rare fault.

This failure manifests as a rupture torn from one side of the inlet filter. Since the tear extends toward the inner side of the filter, it cannot be spotted from a normal viewing angle. Consequently, 

the damage often remains undetected until the unit shuts down for maintenance and filter replacement.

How does this phenomenon occur? We took photos inside the failed inlet filter and found its interior covered with a thick layer of black carbon deposits. 

The cross-section of the rupture indicates these carbon deposits accumulated gradually over a long period.

The company’s compressed air station is located in the northern section of the factory, adjacent to a national highway and surrounded by farmland on three sides, enjoying favorable air quality. 

The station is hundreds of meters away from the production workshop. Although a certain amount of flue gas is generated in the workshop, its pollution impact on the compressor is insignificant. 

Therefore, poor ambient air quality is unlikely to be the root cause of the inlet filter tearing, though this possibility cannot be completely ruled out.

When the compressor inlet filter is torn, the compressor directly draws unfiltered ambient air. This is comparable to a patient exposed to bacteria without wearing a mask, 

carrying severe risks. Although the air surrounding the air station is relatively good, flying insects, dandelion seeds and other debris can drift into the workshop. 

These foreign objects can directly enter the compressor through the torn filter. If contaminants are sucked into the rotors of the airend, the screw rotors may be abraded. 

In severe cases, ingested particulate matter can cause rotor damage or rupture, triggering serious safety accidents.

Judging by the degree of tearing, tremendous instantaneous force was required to rip the filter mesh. This means the inlet filter was so heavily clogged that airflow was nearly blocked. 

Under such conditions, the compressor’s suction force tore the filter mesh to secure air supply. Unfortunately, the torn area falls within a visual blind spot during routine inspections. 

The damage can hardly be discovered unless the inlet filter is removed for replacement.

Clogging of the inlet filter triggers alarms. In practice, two types of alarms are commonly encountered: alarms triggered upon reaching scheduled operating cycles, 

and alarms indicating filter clogging. Operators frequently encounter these alerts. Sometimes the alarm disappears after pressing the reset button, 

and the compressor continues running normally. This is where operators tend to become complacent.

After repeatedly dismissing so-called "false alarms", the compressor will stop generating alerts and tear the inlet filter directly, with no further fault signals displayed. 

Under such circumstances, the damaged inlet filter cannot be detected in a timely manner.

Admittedly, this type of failure is encountered for the first time by our team, and similar incidents are uncommon. Around the time of the failure, 

the local area experienced prolonged low atmospheric pressure, heavy haze and poor visibility. Thick haze filled the sky and permeated the workshop. In addition, 

April brings strong winds and sand dust in Harbin, leading to extremely poor air quality. The newly replaced inlet filter triggered alarms frequently. 

Workers adopted the habitual operation of resetting alarms with one press, unaware that the compressor was operating under abnormal conditions.

Air may look clean to the naked eye, but appearances are deceptive. Air Quality Index (AQI) is now a key indicator followed in weather forecasts. 

Monitoring stations for AQI are deployed at key locations across all districts of Harbin, including our factory site. According to local TV weather reports, 

few monitoring sites record qualified air quality, mainly due to haze. Haze in Harbin is less obvious than in Beijing, yet readings at our factory monitoring station often fail to meet standards. 

Even on seemingly clear blue-sky days, haze persists. As a result, the compressor continuously draws haze-laden air. Although tiny suspended particles are invisible, 

they gradually accumulate as black deposits on the paper filter media of the inlet filter over time. These deposits will clog the filter. On one hand, intake airflow is restricted; 

on the other hand, filter failure will occur once contamination accumulates to a critical level.

If the alarm system malfunctions, inlet filter tearing will take place with even greater consequences. Irregular mesh fragments can be observed at the rupture. 

Debris falling from these fibrous fragments is easily sucked directly into the airend by the compressor suction.

In summary, inlet filter tearing failures demand high attention, as they may trigger catastrophic secondary accidents. 

Only frequent inspections, timely detection and prompt handling can ensure safe compressor operation.