Coalescing Filter Element: The Ultimate Guide

A coalescing filter element helps you protect your critical equipment and components.

But, how does it achieve this?

Usually, compressed air and most of the gases bear liquids and a wide range of particulate contaminants.

This is the point where the coalescing filter element comes in!

In its best form, a coalescing filter element effectively removes the wide range of the liquid contaminants.

These may include water and oil aerosols.

Read on to understand everything regarding the coalescing filter element and its functions.

What is a Coalescing Filter Element?

Before answering this question, firstly take a look at the figure below:

Coalesce Skids

Coalesce  skid

Carefully look at the backside of the skid above.

That is the coalescing filter element.

Quite a significant number of people usually mistake the huge steel lump on a skid’s backside for a coalescing filter.

That is absolutely wrong!

As a matter of fact, it resembles the form of a filter element.

However, you need to acknowledge that it serves a completely different function.

Basically, this element functions by forcing small droplets (the buoyant ones within the gas stream) to crash into other droplets.

Eventually, they coalesce into larger drops and this is the essence of this important equipment.

It is usually about generating larger drops that aren’t buoyant in the gas.

The figure below shows the coalescing filter element in its most basic form:

Coalescing filter element

 Coalescing filter element: photo courtesy: Huffman

Where to Use Coalescing Filter Element

You now have a rough idea of what I’m talking about right?

Now it is time to check out some important attributes about the coalescing filter element.

Firstly, understand that there are two common types of the coalesce filters.

These are the simplex and the duplex coalescers.

Take a look at this:

Turbine Oil Coalesce Skids

Oil coalesce skids

As the name suggests, duplex coalecers implies that the skid has two of these elements.

On the other hand, simplex refers to the case scenarios that only employ one coalesce filter element.

Do you still find this complex?

Don’t worry.

I will walk you through everything step by step and by the end of it all, you will become an expert.

Again, check this out:

coalesce functioning

Coalesce functioning

Please check out the upper section of the figure above.

The arrows indicate the direction of flow.

Let’s now focus on its basic functioning.

However, before that, I’d like to lay great emphasis on the need to purchase the top-performance coalescing filters.

It is common is a matter of common sense that you will always find such from the trusted and leading manufacturers.

Of course, the general-purpose filters can effectively capture large contaminants in the various pneumatic systems.

But don’t get me wrong here!

I don’t mean they can eliminate all sorts of contaminants.

The flow in pneumatic systems will carry along liquid droplets of water and oil and also some minute solid particles.

Never at any moment dismiss these extremely small particles within the flow stream!

As a matter of fact, failure to eliminate them could cause you great and costly problems.

From experience, they end up destroying important parts in just a short period of time.

The close-tolerance valves, foul desiccant dryers, hose inner tubes, and seals are costly parts to repair.

In a bad working condition, they can easily compromise processes such as paint spraying.

Also, they can end up contaminating pharmaceuticals, food and beverage products.

Of course, you don’t want to consume deadly foods and beverages.

Neither do you want your customers or close relations to consume such.

That is why you need to stay on the safe side by installing the coalescing filter element.

Now, let’s expand more on the design of this equipment.

Well, the general design of the coalescing filter element is such that it successfully eliminates the submicron-size contaminants.

You must be asking yourself how it achieves that!

I understand it is getting a little confusing now-but I will explain everything clearly.

Design of the Coalescing Filter Element

The fine fiber meshes form the most important principle in the design mechanisms of the Coalescing filter element.

To perform its role, these fiber meshes usually intercept to enable the capture of the aerosol particles.

Eventually, the smaller particles get amalgamated into larger ones.

As the air moves through the fiber elements, the tiny liquid droplets link up forming larger ones.

Remember that the increase in size is crucial in this particular separation mechanism.

In the new form-the larger co-joined particles- itis much easier to drain them away.

Most probably, you can see that in the figure above and that is the essence of this separation mechanism.

Coalescing filter element

Coalescing filter element – Photo courtesy: Classic Filters

Coalescing Filter and its Operation Mechanisms

I hope this topic is getting easier as we progress.

Next, let’s look at the operational mechanisms of this particular equipment.

Basically, it eliminates contaminants using three working mechanisms:

· Diffusion

You definitely understand that diffusion works for the very small particles.

Probably, these are particles that are 0.1 microns in size and even the much smaller ones.

The Brownian motion results in a collision and eventually, they get trapped by the filter.

It is worthy to note that the solid particles end up adhering to the filter membranes.

On the other hand, the droplets co-join eventually forming larger masses that can be drained away.

· Direct impact

This case scenario involves particles that are 1 micron and larger.

Remember that the collision must take place for the fibers to trap the particles.

Also, it is important outlining what usually happens in a typical coalescing filter unit.

That may help you understand the concept much better.

As a matter of fact, air usually finds its way through the housing,

It then bypasses the media from the inner section and then to the outer area of the filter element.

Where I’m I leading you to?

Well, the coalesced water and oil droplets form on the surface of filter fibers.

Eventually, these particles grow in size and eventually move downwards because of gravity.

At the base of the housing, there is a bowl and that is where the liquid settles.

You can now guess what happens next!

The particles are drained away eventually, but also remember that clean air moves out through the outlet via the outlet port.

But, what are some of the other things that these coalescing filters are capable of eliminating?

Fundamentally, it can also get rid of contaminants such as rust, dust, and dirt.

I hope you know how the defective the above stipulate elements can get upon accumulation!

They can restrict flow a great deal and it gets ugly when the filter media blocks!

Definitely, this is not what you want. Is it?

Now, let’s focus on the interception.

· Interception

You need to understand that this only works for particles that are about 0.1 to 1 micron in terms of size.

In this particular case, it is the turbulent flow that ends up forcing particles against the fibers.

You can guess what happens next.

Can’t you?

The filter matrix eventually captures these minute particles.

Also, note that the smaller the pore size, the higher the capture efficiency.

Features of the Coalescing Filter Element

Coalescing filter element

Coalescing filter element

  • Check out the list of the various features of the coalescing filter element:
  • Helps you to completely eliminate the Sub-Micron Contaminants
  • Idea for the various Adsorbent gases
  • Topmost performance in the Gas or Liquid service
  • You can easily access the custom sizes
  • Functions quite well in a wide range of the corrosive applications
  • High flow rates, low pressure drops
  • Completely disposable
  • You enjoy high efficiency coalescing

Particulate Filter Elements vs. Coalesce Filter Element – Ultimate Comparison

It goes without saying that we all seek to find top solutions to all out filter problems.

You won’t be the first customers interested in learning the difference between the particulate and the coalescing filtration systems.

In fact, we get these questions quite often from most of our customers.

Basically, Particulate filtration involves the separation of solid particles from liquid or gas.

In order to maximize the service life, the liquid or gas usually flows through the element from the outside to the inside.

By the way, do you want to know the secret to determine what works in eliminating the different particle sizes?

Particulate filter element

Particulate filter element

Well, you need to pay focus to the grade of the filter element you go for.

Leading companies will always present you with sizes ranging from the 0.1 micron grades to 200 micron.

Right now you must be curious to know something about the coalescing filtration.

It is crucial to begin by outlining that you can achieve so much with this mechanism.

Of course, that is in terms of contaminants removal.

This filtration mechanism entails the elimination of water droplets and aerosols from gas.

As shown earlier in this outline, it is the coalescing filter element fitted in the housing that enables the filtration.

Remember that the housing bears some three ports that facilitate drainage.

The other thing you need to know is that the wet gas moves from the inner section to the outer area.

The long and the short of it is that the outer happens to be the coarser drainage layer.

On the other hand, the inner capture layer performs its function as the high efficiency coalescing layer.

Also, as indicated earlier, the fine fibers in the case of the coalescing filter play a crucial role.

Coalescing filter

Coalescing filter

They lie on the inner layer where they help capture the fine liquid aerosols.

The formation of larger drops is an important aspect of the entire process.

Definitely, you now know that the large drops are worked upon by gravity.

Eventually, they are pushed downwards to the bowl of the housing.

The other thing you should know is that the coalescing filter elements also eliminate particulates.

However, that is not the main point!

The point I want to put across is that it eliminates contaminants with the same efficiency of the particulate elements.

Actually, I’m refereeing to the particulate type elements that are of the same grade to those of the coalescing filter elements.

But even with that said, there is one more thing to say along this particular line.

Well, the opposite cannot be achieved and thus don’t make a mistake.

Don’t at any point be tempted to use a particulate element in cases where you should use coalescing filter element!

Important Points you Should Know about Coalescing Filter Elements

Remember that contaminations levels, volume, and efficiency of the incoming air are crucial attributes.

You are most probably wondering why?

It is simple.

They absolutely determine the useful life of your filter element.

Obviously, there exists a wide range of selection criteria.

These may include the flow capacity as well as the pressure limits.

However, you need to put it at the back of your mind that what matters the most is the level of efficiency.

Basically, efficiency has to do with the ability of the element to capture particles expressed in percentage form.


Coalescing – Photo courtesy: Parker

Fundamentally, filter ratings vary depending on the product in question.

Of course, that may vary from about 90% to more than 99.99%.

As the user, you need to take it upon yourself to clearly specify products depending on your particular application requirements.

Definitely, most of the efficient filters will usually go at higher rates as compared to the less efficient ones.

I trust you know what is good for you!

The other thing about the more efficient filters is that they are associated with higher pressure drops.

Asides from that, they usually pull along with shorter service lives.

Also, note that the operating expense and performance of the coalescing filter greatly depends on the point of installation.

You should firstly install a prefilter before you move ahead to install the coalescing filter element.

Indeed, this should be a 3-micron unit.

Probably, you must be wondering what the real essence of this is.

It is simple.

This helps you to eliminate quite a huge deal of the particles before the flow reaches the coalescer.

Most at times, this will in a major way to help you increase the life of your coalescing filter.

You will also quite agree that there are those cases where the compressed air presents different cleanliness requirements.

Of course, that is in the different circuits.

Please focus on installing the coalescing filters at the point of use locations that require the cleanest air.

Also, recognize that you end up saving so much money when you follow the right directives.

Did you know that using coalescing filters most at times helps cause a 2 to 6 psi drop downstream?

This is indeed true!

Remember to always factor the pressure loss and you will achieve that by focusing on equipment selection and sizing.

I’d also like to lay emphasis on the great need for you to replace any of your filters.

Always remain observant and any time you notice that they are clogged, proceed and replace them.

Well, here is the rule of thumb-a pressure drop increase from 8 to 10 psi should serve as a warning.

It is definitely the early sign that your filter needs replacement since it is nearing the end of its life.

Of course, you should start making plans for purchasing a new one from a trusted supplier.

All in all, it is also important to outline that the coalescing filter lacks the capacity to eliminate oil vapor.

Probably, this is starting to worry you again.

Anyway, this shouldn’t be a cause for alarm since it is a pretty easy matter to resolve.

What you need to do is basically find the adsorption filters or the activated carbon.

Using these along with the coalescing unit will help you a huge deal towards obtaining extremely clean air.

One instance when one requires such air is for breathing purposes.


Of course, I have walked you through the important aspects you need to know regarding the coalescing filter elements.

At this point, I wish to lay great emphasis on the need for you to consider everything in this guide.

I believe just like the rest of our customers you believe in reliability and optimal performance.

In case you have any questions for us, we work around the clock to ensure that you are satisfied.

It will be fine reaching out to us via a phone call or through our website.

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