Why Is The Air Compressor Oil Water Separator Clogged?

The air compressor oil water separator plays an important role in the compression process of air. It ensures that oil, water and other harmful substances do not end up in the compressed air system and pipe.

It consists of many parts, but each has its own unique and indispensable role. When the oil water separator get clogged, you could be in big trouble.

Let’s see how to solve!

What Is the Air Compressor Oil Water Separator?

The air compressor oil water separator is a component that separates oil and water in compressed air, and removes oil dirt and moisture in the air

It has three functions:

  1. Ensure that the discharged compressed air is clean.
  2. Prevent the backflow of compressed air in the pipeline.
  3. Ensure that the inside of the air compressor reaches the pressure required for lubricating oil circulation.

How Does An Oil Water Separator Work?


As compressed air cools, it produces condensate — a mixture of oil, water, and other contaminants. This condensate is initially collected in a compressor’s separator, filter, or air receiver.


The collected condensate is then sent to the oil-water separator. Through the principles of gravity separation and/or coalescence, the unit separates the oil from the water.

Gravity separation

Since oil is lighter than water, it naturally rises to the top. The separator exploits this property to segregate the oil from the water.


This method employs a polypropylene element or other types of filter media. As the condensate passes through these materials, the oil particles merge (or coalesce) and form larger droplets, which then rise to the surface due to their lower density.


The water, now relatively clean, is safely discharged into the general waste system following local wastewater regulations. The oil is collected for proper disposal or recycling, ensuring environmental safety.


Many oil-water separator systems include an automatic shut-off system or warning device. This alerts the operator if there’s an issue with the separator or when it’s time for regular maintenance and cleaning.

The Structure of Air Compressor Oil Water Separator

An air compressor oil water separator contains several key components that all cooperate to keep the environment clean of pollutants. Let’s take a closer look at each part:

Tank Body

This vessel serves as the primary storage site for the oil-water mixture and further processes. It’s suitably proportioned to be able to handle the volume and pressure of the liquids it contains.

Oil Separator Core

This part enables the oil to be separated from the water. As the mixed liquid passes through the core, oil particles coalesce, forming larger droplets which separate due to their lighter density in comparison to water.

Oil Return Pipe

This pipe system allows the collected oil from the separator core to be redirected and reused in the compressor or stored for disposal, depending on the specific system design.

Safety Valve

This device safeguards the system by releasing pressure if it exceeds a set threshold, preventing potential issues resulting from overpressure.

Minimum Pressure Valve

This valve maintains a certain level of pressure in the separator to ensure it operates efficiently. It prevents the system’s pressure from dropping too low, which could impair its performance.

Pressure Gauge

This instrument measures the pressure within the system, enabling operators to monitor operation and detect any potential issues early.

Oil Level Glass

This component offers a visual method for operators to monitor the oil level within the system, helping them decide when to dispose of the oil or if more oil needs to be added.

Refueling Hole

This is a designated opening on the tank which is used when there’s a need to refill the system with oil.


Explore Screw Air Compressor Valve Types: The Ultimate Guide

Unloader Valve
Check Valve
Minimum Pressure Valve
Oil Stop Valve
Temperature Control Valve
Solenoid Valve
Vent Valve
Capacity Regulating Valve
Drain Valve
Bypass Valve
Inverse Proportion Valve

Click to check the 11 main air compressor valve types, and how do they work.

Consequences of the Air Compressor Oil Water Separator Get Clogged

A clogged air compressor oil-water separator can have several detrimental consequences that can affect the system’s performance and operational costs.

Decreased System Efficiency

When the separator is clogged, the compressor has to work harder to maintain the same level of performance. This can lead to decreased efficiency and higher energy consumption, which translates into increased operational costs.

Air Compressor Damage

Clogs can result in increased pressure within the air compressor system. If not addressed, this elevated pressure can cause damage to the separator itself and other components of the system, potentially leading to costly repairs or replacements.

Decreased Lifespan of the System

A clogged separator puts undue strain on the entire compressor system, which can reduce its overall lifespan.

Poor Air Quality

When the function of the separator is impaired, the quality of air produced by the compressor can degrade. If the compressor is being used in applications where air cleanliness is important, like medical or food manufacturing, this could have severe consequences.

How Can You Tell If the Separator Isn’t Clogged?

Decreased efficiency in compressor operation, heavily oily or discolored discharge water, or an activated warning device.

Causes of the Air Compressor Oil Water Separator Get Clogged

Inadequate Separator Size

If the separator is too small for the volume of compressor condensate being processed, it may become overwhelmed and clog. This is often an issue when the compressor use exceeds the separator’s capacity, or if the compressor has been upgraded but the separator has not.

Extreme Operating Conditions

Intense cold or heat can affect the separator’s performance. Cold can solidify oil and make it harder to separate from water, eventually leading to clogging, while high heat can cause breakdowns in components or the formation of sludge, which can block pipes and filters.

Corrosive Gases in the Environment

The presence of corrosive gases, such as sulfides and other volatile chemicals, in the surroundings of the air compressor can lead to chemical reactions with the machine oil. This results in the formation of carbon deposits and sludge.

Some impurities entering the oil circulation system are intercepted by the oil filter, while others, carried upward with the oil-gas mixture, get trapped in the filter paper of the oil separator, clogging the filtering holes of air compressor oil water separator.

Improvement Solutions:

– Install a pre-filtering device at the air compressor’s inlet.

-Install high-volume exhaust fans in opposite directions in the compressor room to accelerate air circulation, diluting air pollution concentrations.

– Relocate the compressor room to a place with relatively better air quality.

Use of Unqualified Air and Oil Filters

Low-precision air filters allow dust particles to enter the compressor system, increasing the load on oil filters and causing premature clogging.

Impurities entering the compressor system, along with oxidized oil and worn metal particles, get intercepted by the oil filter’s poor filtration precision. Some impurities remain in the oil filter layer, while others circulate inside the machine until reaching the oil separator, causing premature clogging.

Poor-quality oil filters open their bypass valves after a few hours of use, allowing unfiltered oil to circulate in the system.

Poor Quality Oil or Coolant

Sometimes, using low-quality or incompatible oil or coolant can lead to increased contamination, resulting in a clogged separator.

Moreover, the use of oil with poor oxidation resistance, even for short periods, can result in carbon and gel formation, leading to oil separator blockages.

Leakage in the Air Filter System

There is a problem with the sealing of the contact surface between the air filter and the air filter assembly. There are several reasons!

  1. The air filter is not installed properly (wrong size)
  2. The contact surface of the air filter assembly is uneven (the air filter assembly is deformed) cause leakage
  3. There is dirt attached to the contact surface between the air filter and the assembly
  4. The elastic contact pad on the surface of the air filter is crooked.
  5. The air filter or air filter assembly is broken
  6. Leakage in the middle of the intake hose, caused by aging or poor installation
  7. Leakage at the seal between the intake valve and the compressor head, possibly due to damaged gaskets

Excessive Moisture on the Oil Separator Filter Material

  1. Leakage at the minimum pressure valve allows external airflow, which, after machine shutdown, condenses into water droplets in the oil separator. These water droplets enter the filter material, causing it to expand and deteriorate.
  1. Low usage and short load times of the compressor can result in inadequate moisture discharge, leading to water retention in the oil separator filter material.
  1. Prolonged operation below 75°C prevents the timely discharge of moisture, causing it to accumulate in the oil separator filter material.

Understanding and addressing these issues is crucial for maintaining the efficiency of air compressor oil-water separators.

How to Maintain the Air Compressor Oil Water Separator?

Regular check-ups and cleaning of the separator system are critical. If maintenance is overlooked, the unit’s filters can become clogged with debris or sludge, restricting its functionality.

The following are common maintenance methods:

Regular Inspection

Regularly inspect all separator components for any visible damages or changes. Keep tabs on the oil level and watch out for changes in color or consistency.


Cleaning the tank and the components regularly can help avoid accumulation of sludge or debris that could lead to clogs. The cleaning intervals depend on the specific model and usage but to be on the safe side, establish regular cleaning schedules.

Filter Replacement

The filter is a crucial component of the separator and needs to be changed periodically. The frequency again depends on the manufacturers, models and operation times, but a good practice is to replace it every 1,000 operational hours or at least annually.

System Flushing

On scheduled intervals, a complete system flush is advised. This involves running a specially designed cleaning fluid through the system, removing any remaining or stubborn debris.

Professional Maintenance

It’s advisable to have a professional technician perform a comprehensive inspection of the separator system periodically. This is crucial in identifying and addressing underlying issues early.

Use High-Quality Oil

Using high-quality oil can lessen the amount of sludge and other contaminants that can gather in the system, ensuring better performance.

Correct Separator Size

Confirm that the separator’s size is appropriate for the volume of condensate it’s managing. Reassessment might be needed if significant changes in the compressor’s usage have happened.

Monitor Operating Conditions

Keep an eye on your compressor’s operating temperatures. Particularly hot or cold conditions can affect performance and potentially cause issues.

Reasonable running time and air output

The maintenance of the entire compressed air system (inner chain) is relatively complex, among which the air output and operating time are the most easily overlooked.

Reasonable running time and consistent air output are the basic conditions for maintaining an air compressor. If the air compressor has low air flow or be in downtime for a long time, it may cause failure.


What Is The Compressor Air End And How to Choose?

Another core component of the air compressor is the air end.

Understanding the air end and choosing the right one for your needs can ensure the efficiency and reliability of your compressor.

Whether you’re a seasoned professional or new to the industry, this article will provide you with valuable insights into the air end of a screw compressor and help you make informed decisions when selecting one.

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