Practical Analysis on Common Problems of Air Compressor Oil Filters

1. Bottom Perforation of Oil Filter

Apart from a small number of cases caused by sand holes on steel plates, bottom perforation is mostly attributed to poor material quality of the filter housing steel. 

Although housing thickness exerts some influence on perforation risk, it is not the primary factor. Inferior steel is prone to corrosion and eventual perforation at the bottom where water and impurities settle, 

analogous to a person with weak immunity catching a cold easily under mild exposure. Steel quality is decisive. High-quality oil filters may occasionally suffer bottom perforation, yet the probability remains extremely low.

2. Oil Leakage at Sealing Ring
Sealing ring material defect: Poor temperature resistance causes the sealing ring to shrink after a period of service, resulting in oil seepage or leakage.

Poor perpendicularity of threaded plate thread: The threaded plate fails to maintain a strict 90° vertical angle, leading to uneven circumferential sealing. 

The allowable inclination error on either side is 0.3 mm; any deviation beyond this limit is non-conforming. No leakage occurs immediately after installation thanks to elastic compensation of the seal. 

After prolonged operation, thermal shrinkage reduces seal elasticity on the heavily inclined side, significantly weakening sealing performance and triggering oil leakage.

3. Rupture & Oil Leakage at Crimped Seam

This fault rarely occurs if regular steel is adopted for sealing plates. Ruptures at crimped seams frequently appear on electroplated sealing plates. 

While electroplating creates a uniform surface appearance, the base steel before plating varies widely. Certain steel grades are brittle; though intact after bending and pressing, 

they crack quickly under machine vibration during operation.

4. Oil Leakage at Crimped Seam
Frequent leakage at crimp seams indicates the filter manufacturer only conducts sampling pressure testing during seam machine commissioning instead of leak testing every finished oil filter.
Insufficient coating of sealing compound at crimp joints or adoption of inferior sealant.
Improper commissioning of crimping equipment.

Filters operate leak-free on 8 bar compressors, yet leakage rises sharply on units above 10 bar. This phenomenon mainly stems from thin threaded plates that deform under elevated pressure and loosen the crimp joint. 

Filter paper quality is also highly relevant: inferior filter paper increases internal pressure of the oil filter and imposes extra load on the threaded plate, further loosening crimp seams.

5. Fragile Filter Paper

Many operators discover shattered filter paper when opening spin-on oil filters. The root cause lies in poor anti-carbonization performance of filter media. 

Long-term exposure to high temperature leads to carbonization, making filter paper brittle and prone to fragmentation. External spin-on oil filters encounter the same issue; 

the carbonized media cannot be observed from outside. Fragmented filter paper easily clogs the oil-air separator element.

Note: Fiberglass filter paper can extend anti-carbonization service life by more than 30%.
6. Filter Paper Clogging the Cooler (Sludge Formation)

It is common knowledge that intake air contains moisture. Semi-resin filter paper (starch-blended filter paper) features low resin content and non-pure wood pulp with starch additives, 

resulting in extremely poor water resistance. When semi-resin media absorbs water, it disintegrates into sludge, which blocks the cooler and the surface of oil-air separators.

7. Abnormal Clogging of Oil Filter after Service Period

The clogging discussed herein differs from surface fouling; it refers to abnormal premature blockage of filter media. Moisture inside the oil-air tank narrows filter pore size and reduces throughput. Additionally, 

water absorption causes filter paper deformation and adhesion between layers, drastically degrading filtration performance. This issue frequently occurs on large-displacement compressors. 

It generally appears in full-resin wood-pulp filter paper or semi-resin wood-pulp filter paper.

Note: Full-resin paper is pure wood-pulp filter media; semi-resin paper is wood pulp blended with starch and low resin content. Cured filter paper seldom suffers such abnormal clogging.
8. Failures of WD13145 Oil Filter
8.1 Burst-out Sealing Ring

This failure mostly happens on compressors rated above 15 bar. The sealing ring is extruded and ejected shortly after installation. Many WD13145 filters adopt 5 mm thick threaded plates, 

and some even use 4 mm plates. Under high working pressure, threaded plate deformation pushes out the sealing ring, commonly known as "burst seal".

Furthermore, seal ejection directly correlates with filter paper quality. Inferior media shrinks in pore size and deforms under moisture, compressing filter layers and raising internal pressure of the oil filter. 

Once the threaded plate cannot withstand the pressure, it deforms and dislodges the seal.

8.2 Collapsed Central Core Tube
The central support tube inside the filter is squeezed and deformed for two reasons:
Insufficient structural strength of core tube; thicker core tube is required to improve pressure resistance.
Inferior filter paper absorbs moisture and generates excessive flow resistance, subjecting the core tube to overload compression.
Therefore, WD13145 filters must be equipped with premium filter paper and thickened central core tubes to avoid core collapse.
9. Oil Filters for Variable Frequency Screw Compressors

Under prolonged low-frequency operation, variable frequency screw compressors run at relatively low temperature with abundant moisture accumulated in the oil-air tank, 

imposing higher requirements on the water resistance of filter paper.

Low-frequency operation lowers lubrication circuit pressure. The oil filter must feature low flow resistance and excellent air permeability.

Variable frequency units mostly operate under continuous loading. Compared with fixed-frequency compressors, they accumulate longer effective running hours within the same calendar period. 

Thus filter media needs stronger anti-carbonization capacity and higher dust holding capacity.

10. Service Life of Oil Filters
There is no universal fixed lifespan. The effective service life depends on two factors:
Contaminant load: Service life expires once the filter reaches its maximum contaminant retention capacity.
Operating temperature and anti-carbonization performance of filter paper. High operating temperatures accelerate media carbonization and shorten service intervals. Inferior filter paper wears out rapidly.
Under normal operating conditions, high-quality oil filters offer an effective filtration service life of approximately 2000–2500 hours.
11. Filtration Performance of Oil Filters

What is the function of an oil filter? As the name implies, it removes solid contaminants from lubricating oil — its core purpose. 

Nevertheless, over 95% of people misunderstand its filtration principle.

Many believe oil filters rely purely on surface interception: higher precision delivers better filtration, while ultra-fine precision leads to frequent clogging. 

This is a misconception. Although filtration precision affects performance to a certain degree, the decisive factor is the adsorptive capacity of filter paper. 

Larger dust holding capacity brings stronger adsorption and superior overall filtration efficiency. Fiberglass filter paper achieves excellent performance thanks to large dust holding capacity, 

powerful adsorption and outstanding carbonization resistance.

However, fiberglass media carries a high cost and is not sold in small batches; custom mass orders are mandatory. 

Only manufacturers with substantial filter sales volume can adopt fiberglass paper, explaining why it is rarely used widely.