Maintenance of Consumable Spare Parts for Air Compressor Aftertreatment System

1. Air Filter

The air filter of an air compressor consists of the air filter assembly and filter element. Externally, it connects to the compressor intake valve via joints and threaded pipes to filter dust, 

particles and other contaminants in intake air. Air filters with appropriate specifications can be selected for different compressor models according to intake air volume.

Fault Symptom: Filter Clogging

A clogged air filter will increase energy consumption and waste electricity. Dust can easily penetrate the filter. 

Excessive dust entering the compressor shortens the service life of compressor lubricant and may cause blockage of the oil-gas separator.

Troubleshooting & Maintenance
The filter element is the core component of the filter. Manufactured from special materials, it is a consumable requiring careful maintenance.
After long-term operation, the filter element intercepts a large amount of contaminants, leading to increased pressure drop and reduced flow rate. Timely cleaning is required under such conditions.
Take care to avoid deformation or damage to the filter element during cleaning.

Filter paper is also a critical component. High-quality filters normally adopt ultra-fine fiber paper impregnated with synthetic resin, which delivers efficient impurity interception and high dirt-holding capacity. 

The filter paper must possess sufficient mechanical strength to withstand high airflow, guarantee filtration efficiency and extend equipment service life.

The pore size of filter paper is approximately 10 μm. The element should be removed every 1,000 operating hours to clear surface dust by blowing low-pressure air from inside out.
A differential pressure detector is fitted on the air filter. If the display indicates air filter clogging, the filter must be cleaned or replaced immediately.
2. Oil Filter

The oil filter is generally a paper-type filter. It removes impurities such as metal particles and deteriorated oil products from lubricant, 

with a filtration precision ranging from 5 μm to 10 μm, providing protection for bearings and rotors.

Fault Symptom: Oil Filter Failure
Troubleshooting & Maintenance
The need for oil filter replacement can be judged by its differential pressure indicator. Illumination of the differential pressure warning lamp indicates the oil filter is clogged and requires immediate replacement.

For new units, lubricant and oil filter shall be replaced after the first 500 operating hours. Afterwards, 

replacement shall be carried out once the differential pressure alarm triggers.

If a heavily clogged oil filter is not replaced in time, insufficient oil supply may lead to high exhaust temperature and automatic shutdown. 

In addition, inadequate oil supply will shorten bearing service life.

The effective service life of an oil filter depends on two factors:
Contaminant loading. The service life expires once the filter reaches its maximum contaminant adsorption capacity.

Operating temperature and carbonization resistance of filter paper. The service life differs greatly between high-temperature and normal-temperature operation. 

Continuous high operating temperature accelerates carbonization of filter paper and shortens its usable time.

Low-grade filter paper has a short service cycle. Under normal working conditions, high-quality oil filters offer an effective filtration period of roughly 2,000–2,500 hours.

When variable-frequency screw compressors run continuously at low frequency, operating temperature tends to be relatively low, and more moisture accumulates inside the oil separator tank. 

Therefore, the filter paper must feature excellent water resistance. Low-frequency operation also results in low pressure inside the oil circuit system, 

which requires oil filters with low flow resistance and good air permeability.

Many people hold the misconception that oil filters rely purely on surface interception — the higher the filtration precision, the better the effect, 

while worrying that ultra-high precision will lead to frequent clogging.

Research shows this viewpoint is incorrect. Although filtration precision has some relevance to performance, the decisive factor is the adsorption capacity of filter paper. 

Higher dirt-holding capacity brings stronger adsorption and superior filtration performance.

Fiber filter media achieves excellent performance thanks to large dirt-holding capacity, strong adsorption and outstanding anti-carbonization properties. Nevertheless, 

fiber filter paper is costly and only available via bulk customized orders. Customization is uneconomical for manufacturers with moderate filter sales volume, which explains why fiber media is rarely adopted.

3. Oil Separator Element (Oil-gas Separator Core)

The oil-gas separator element is constructed with multiple layers of fine fiberglass. It can almost completely remove oil mist entrained in compressed air. 

Under normal operating conditions, its service life is around 3,000 hours.

Water-oil separation cartridges are specially designed for liquid-liquid separation, consisting of coalescing cartridges and separation cartridges.
Consequences of oil separator element failure:
Poor separation efficiency leads to high lubricant consumption and excessive oil content in compressed air, disrupting downstream purification equipment and end-user machinery.
Clogging increases pressure drop, raising actual exhaust pressure of the unit and boosting power consumption.
Deterioration causes fiberglass filter media to peel off and mix into lubricant, shortening oil filter life and triggering abnormal wear of the main airend.
A ruptured separator element leads to severe oil carryover, heavy lubricant loss, high unit operating temperature, and in serious cases, seizure of the airend.
Fault Symptoms: Clogging / Rupture / Burning / Poor Separation Performance
Troubleshooting & Maintenance
Lubricant quality and ambient pollution level have a significant impact on service life. A pre-filter can be installed if the operating environment is heavily contaminated.
Clogging

Clogged oil separator elements cause excessive motor current. Excessive differential pressure may deform the element, resulting in motor overload or even airend seizure. 

In addition, overcurrent accelerates contactor aging or burns contacts, potentially triggering severe accidents.

Most screw compressors are equipped with pressure gauges before and after the separator element. The oil separator element needs replacement when the pressure difference reaches 0.08 MPa.
Rupture

Obvious symptoms include excessive oil consumption and substantial oil accumulation inside the air receiver and pipelines. In severe cases, 

compressor lubricant is directly discharged through the drain valve of the air receiver.

Root causes:
(1) Failure to replace the element on schedule;
(2) Adoption of low-quality oil separator elements;
(3) Non-compliant installation operations, e.g., puncturing the element during oil return pipe fitting.
Burning
Although not frequent, element burning occurs occasionally during operation. Typical signs include partial or full carbonization of the filter mesh, and even melting of the metal housing.
Root causes:
(1) Poor quality of compressor lubricant;
(2) Inferior quality of the oil separator element itself;

(3) Poor electrical connection between the element housing and oil separator tank during installation. Lack of reliable grounding leads to static electricity accumulation, 

which ignites oil mist and burns the element.

Poor Separation Performance
Main symptom: Excessively high oil content in compressed air, causing damage to downstream aftertreatment equipment and user production machinery.
Root causes:
(1) Inferior quality of the oil separator element;
(2) Non-standard installation procedures.