Guide to Coalescing Filters

Filters, especially coalescing filters, are essential in many industrial applications where manufacturers and refineries need to ensure a pure, high-quality product. Contaminants like water, vapor, gases and particles can make their way into a fluid or gas, decreasing its quality and damaging the effectiveness of system equipment downstream. Coalescing filters are a crucial step in preventing contamination from liquid and vapor droplets. A coalescer is used across oil and gas, chemical processing, and alternative fuel industries to remove entrained liquids from gas streams, protecting downstream instrumentation, compressors, and end-use equipment.

Coalescing filters are crucial in various industrial and chemical applications. Manufacturers can use them for gas-oil, fuel-gas and water-gas separation. This guide will explain the benefits of coalescing filters, so you can determine which filter best fits your application.

Contact Us for Filters

What Is a Coalescing Filter?

A coalescing filter or coalescer filter is a piece of equipment that filters droplets of liquid and vapors out of a substance. Coalescing is the process by which small liquid particles suspended in a gas stream are forced together to form larger droplets that can be efficiently drained, making it a highly effective method for achieving dry, clean gas output. A coalescing filter is a specialized piece of industrial equipment designed to separate liquid droplets and vapor from a gas or fluid stream using the principle of coalescence. This coalescer filter uses a process called coalescence to separate two phases of matter from a mixture. So what is coalescing? Coalescence is the process of two or more droplets or bubbles of a substance merging into one larger droplet, which filters out easily because it is heavier. Coalescence filtration can remove matter as tiny as 0.1 microns or smaller.

Many industries use coalescing filters, though the type they use depends on their application. At some stages, a gas coalescer filter separates contaminants in the gas phase, while others efficiently remove liquid droplets. Coalescing filters can remove water, methane, carbon dioxide, sulfur, oil and other liquid or gas impurities.

The coalescer filtration process can use two primary types of coalescing filters.

• Mechanical coalescing filters: Most industries predominantly use the mechanical coalescing filter. This filter removes impurities using a series of baffle walls or screens to trap water and vapor molecules.
• Electrostatic coalescing filters: The less common type of coalescing filter, called the electrostatic coalescer, uses electric currents to remove liquid molecules.

Implementing coalescing filters in an industrial application aims to prevent contamination of the fluid or gas that needs filtration and avoid corrosion of other system components. With a coalescing filter, manufacturers can ensure a pure end-line product and keep damaging liquid and gas impurities out of their refining equipment.

Functions and Elements of a Coalescing Filter

Precision filtration is essential in applications that rely on coalescing filters. Coalescing filter media consists of multiple progressing fiber layers — typically borosilicate microfiber or semi-permeable membranes — that strain aerosols and captured liquids through the filter wall. The coalescing filter’s densely packed layers strain out aerosols and captured liquids through the filter wall.

For a coalescer filter to ensure product purity, the substance that needs filtering must go through the following process.

• Fluid gets applied to the filter: The filter must have a fluid or gas stream applied to it. Usually, coalescing filters contain two or more filter points to ensure efficient contaminant removal.
• The coalescing filter separates the components: When the fluid passes through the filter, the fiber or screen separates the liquid. The filter mechanism works based on the components’ molecular weight and density. The filter traps substances like oil, water droplets and gases, while the rest of the pure fluid or gas continues through the system to the collection points.
• The impurities coalesce: The droplets left behind then coalesce into heavier particles that drain away through the filter wall by gravity. You can either dispose of or purify the remaining contaminants.

A fuel gas filter coalescer works differently based on the component substance’s properties. For example, when removing oil from water, the screens redirect the heavier oil molecules to a drain point and allow the less dense water molecules to filter through. Similarly, “wet gas” — a gas containing water droplets — gets dehydrated when it passes through the coalescer, as the dense water molecules coalesce into the bottom of the tank. The coalescing element is the heart of the filter, typically constructed from layered borosilicate microfiber media that captures and merges fine aerosol droplets until they are large enough to drain by gravity from the filter housing.

Coalescing Filters vs. Other Filtration Types

Not all filters handle the same contamination problem. Understanding the difference between coalescing, separation, and particle filtration helps you specify the right solution for your system and avoid costly misapplication.

Coalescing Filters are engineered for one specific task: removing fine liquid aerosols and mist from a gas or liquid stream. They work by accumulating submicron droplets on their fiber media and merging them into drainable bulk liquid. If your contamination is oil mist in compressed air, water aerosol in natural gas, or hydraulic fluid carry-over in a pneumatic line, a coalescing filter is the right tool. They are not designed to handle particulate contamination or high bulk liquid loads — that is where separators and particle filters come in.

Liquid-Gas Separators (also called knock-out drums or demisting separators) handle bulk liquid removal using centrifugal force, baffles, or gravity. They are used upstream of coalescing filters in high liquid-load applications where the volume of liquid entering the system would quickly overwhelm and flood a coalescing element. Separators cannot remove fine aerosols below approximately 10 microns — which is exactly the range where coalescing filters begin. In demanding pipeline and compression applications, separators and coalescers are used in series, with the separator taking the bulk load first.

Particle Filters (depth-type and surface-type) capture solid contamination: metal fines, pipe scale, catalyst particles, and other particulate matter. They filter by size exclusion, not by liquid coalescence. Some systems require particle filtration upstream of a coalescing filter to protect the coalescing media from premature plugging by solid contamination. The key difference is the contamination phase: particle filters target solids, coalescing filters target liquids, and separators target high-volume bulk liquid.

In most industrial compressed air and gas systems, the correct specification is all three in sequence: separator to remove bulk liquid, particle filter to remove solids, and coalescing filter as the final polishing stage for clean, dry output. Chase Filters manufactures all three types and can help specify the right combination for your system pressure, flow rate, and cleanliness requirements.

Contact Chase Filters

Coalescing Filter Applications

Where are coalescing filters used? They fulfill multiple applications in industries that require or produce pure liquid and gas, like the oil, gas and chemical processing industries. A liquid gas coalescer filter separates entrained liquid droplets from a gas stream by forcing the gas through layered fiber media, where droplets merge and drain by gravity before the cleaned gas exits.

1. Alternative Fuel

Alternative fuel industrial filter applications include compressed natural gas, propane, electricity, methanol and more. A fuel gas filter coalescer is used upstream of combustion equipment and turbines to ensure that any entrained water or liquid hydrocarbons are removed before the gas reaches the burner, protecting efficiency and equipment life. Filters like stainless steel coalescing filters are essential for efficient operation in the following specific fluid applications:

• Aboard a CNG vehicle.
• Product Refining
• De-Humidify Natural Gas
• Purify Natural Gas
• In polyethylene terephthalate blow molding.
• At CNG fueling stations.
• When storing high-pressure air.
• To filter high-pressure compressed gas.
• Prevent Corrosion in the following:
• Compressors
• Amine/Glycol Absorbers
• Turbines

2. Chemical Processing

Filtration is crucial in chemical and polymer processing operations because the products must meet strict legal requirements. Proper quality control and filtration can ensure the product’s meet all requirements and keep operating costs low. Coalescing filters are highly effective in removing liquid and vapor contaminants from the chemicals, Air, Gas and fluids used in chemical processing. The following applications use chemical processing filters:

• Cooling and processing water used as an ingredient, coolant or washing medium.
• Manufacturing and processing liquids and pastes.
• Filtering hot gas.

3. Oil and Gas

In oil and gas energy production, downstream coalescing filters ensure the product’s purity before marketing. For example, before using crude oil for fuel or as feedstock in chemical processing, the oil refinery must separate it into various components. This process is called refining, and it involves using an oil coalescing filter inside distillation units to de-humidify and purify the crude oil. A natural gas coalescing filter is a critical component in pipeline and processing systems, efficiently removing water vapor, liquid hydrocarbons, and aerosols that could compromise flow meters, compressors, and gas turbines.

Alternative energy sources like natural gas must undergo processing and refining to separate the gas from liquid and aerosol contaminants. A gas coalescer is essential for natural gas and compressed gas pipelines, removing liquid aerosols and contaminants that can damage compressors, meters, and other downstream equipment. These substances include condensate, water, acid gas and mercury. Applications of oil and gas coalescing filters in downstream production include:

• Cooling water treatment.
• Fluid analysis.
• Fuel additive process.
• Gas purification.
• Process controls.

Coalescing filters are among the most versatile filtration solutions available, serving industries from oil and gas to aerospace and alternative fuel. Understanding their design and function helps engineers select the right coalescing filters for their specific application.

Benefits of Coalescing Filters

Numerous companies across various industries use coalescing filters in their operations. Industrial professionals use this equipment because they have experienced its many benefits, including the following.

1. Effective Filtration

Coalescing filters are highly efficient at coalescing and removing liquid and vapor contaminants. Depending on the coalescing filter design and product, they can have a 95% to 99% micron removal rate. Coalescing filters are also efficient against 0.01 microns.

At Chase Filters & Components, we guarantee 99% efficiency with our 57 Series coalescing filters because they have withstood vigorous efficiency testing. Our stainless steel and aluminum filters include C- or CS-grade elements designed to withstand temperatures of up to 900 degrees Fahrenheit and are ideal for heavy coalescing.

2. Protects Downstream Equipment

Fluid cleanliness is essential to proper system function. Contaminated fluid and gas can erode machine components and lead to deterioration. Installing coalescing filters at the appropriate locations within your industrial system can prevent these issues from occurring and protect your equipment downstream. At Chase Filters & Components, our coalescing filters are also corrosion-resistant and durable, so they can keep working for you longer.

3. Reduces Expenses

Preventing system malfunction is vital in reducing an industrial facility’s operating expenses. When system parts deteriorate quickly, they can result in overall system failure. Repairing or replacing these parts is costly, yet it could be necessary if the damage progresses. Poor system performance also leads to decreased facility efficiency. It can also increase downtime and drive up costs.

4. Custom Coalescing Filters

If your application requires an unusual or outdated part, creating a custom filter with Chase Filters & Components can keep your systems running as they should. Investing in a custom filter can prevent machine wear and tear, ensure product purity and decrease maintenance costs associated with poor system performance. Chase Filters & Components can design and manufacture a custom filter to match your existing equipment.

Request a Quote Today

Check out Coalescing Filters From Chase Filters & Components

Coalescing filters are essential in many industrial applications. Implementing these filters in your operations can maintain the quality of your fluids and gases, so you can ensure they are ready for the user. Coalescing filters can also benefit industrial manufacturers by helping them prolong the life of their system machinery and reduce operating costs.

Coalescing filters from Chase Filters & Components are your solution for filtering liquids and vapors in your applications. Check out our selection of coalescing filters today.

Jump To: 

• What Is a Coalescing Filter?
• Functions of a Coalescing Filter
• Coalescing Filter Applications
• Benefits of Coalescing Filters

Coalescing Filter FAQS:

Q: What is a coalescing filter?

A: A coalescing filter is a type of filtration device that captures fine liquid droplets suspended in a gas or liquid stream and causes them to merge (coalesce) into larger droplets that can be drained or removed. They are commonly used to separate water, oil mist, and aerosols from compressed air, natural gas, hydraulic fluid, and other industrial fluid streams.

Q: How does a coalescing filter work?

A: Coalescing filters work by directing a contaminated fluid stream through a porous filter media. As small droplets pass through the media fibers, they collide and merge into progressively larger droplets. Once large enough, gravity pulls these droplets downward into a sump or drain, effectively separating them from the clean fluid stream. The working principle relies on interception, impaction, and diffusion within the media.

Q: What is coalescing filter media made of?

A: Coalescing filter media is typically constructed from borosilicate glass microfibers, synthetic polymer fibers, or a combination of both. The media is engineered to specific pore sizes and fiber diameters to target droplet sizes in the 0.01 to 0.3 micron range. Material selection depends on the fluid being filtered, operating temperature, and chemical compatibility requirements.

Q: What are coalescing filters used for?

A: Coalescing filters are used in compressed air systems to remove oil mist and water vapor, in natural gas pipelines to remove liquid hydrocarbons, in hydraulic systems to prevent water contamination, in aerospace applications for fuel and oxygen system protection, and in industrial manufacturing wherever clean, dry gas or fluid is required for process or equipment protection.

Q: What is the difference between a coalescing filter and a separator?

A: A separator removes bulk liquid from a gas stream using centrifugal force, baffles, or gravity, typically handling high liquid loads. A coalescing filter removes fine aerosols and mist (droplets below 1 micron) that a separator cannot capture. In demanding applications, both are used in series: the separator handles the bulk liquid first, then the coalescing filter polishes the remaining fine droplets.

Q: How do I choose the right coalescing filter for my application?

A: Selecting a coalescing filter requires evaluating five factors: (1) operating pressure and pressure drop budget, (2) flow rate and velocity through the media, (3) the type and concentration of contaminants to be removed, (4) temperature and chemical compatibility of the media and housing materials, and (5) downstream cleanliness requirements measured in micron rating or oil carryover limits in ppm. For high-pressure applications above 3,000 PSI, housing material and seal selection become critical.