How to Choose an In-line Filter – 4 Key Things to Know

ISM filters puzzle featuring the Clear-VU EZ Connect™ and ITW Fastex in-line filtersSelecting the Right In-line Filter

What happens when you set out to find the right in-line filter? This is tougher when looking for a miniature filter. I always think about the one I have and go looking for another just like it. What if there is no specific example to replace? Try searching for how to choose a filter using Google. Sorting through what matters and what doesn’t is a chore.

I’m going to review some tips on how to think about filter features so you end up with more filter options with less effort.  This blog refers to commercial filtration. Choosing medical filtration involves different considerations.

An exploded view of an ISM modular check valve. Click here to go to a landing page where you can get more information about these valves.

Modular Check Valves

We've taken spring-loaded check valves to a whole new level. Mix and match imperial and metric connections. Watch the video.

A play button for a video about ISM's modular check valves. Click here to go to a landing page where you can watch the video.

1. Particle Separation
Filtration is the separation of particles from a liquid or gas stream. Generally, filtration involves one of the following:

  • Separating particles from the flow. What do you need to remove from the liquid or gas stream?
  • Removing gas from a liquid. Are bubbles a problem?
  • Removing liquid from a gas. Do you need to protect sensors from contact with liquids or vent a chamber?

2. Chemical Compatibility
Are the chemical compatibility needs the same for both the filter housing and the filter element?

Caustic, acidic, organic solvent…the variety of liquids and combinations of liquids make chemical compatibility one of the most important issues when choosing a filter. Reactivity is not limited to extreme chemicals. Water, oils and fats can leach chemicals from the filter housing or filter material. Higher temperatures increase chemical leaching. Chemical compatibility charts are your friend.

3. Operating Conditions
Let’s face it; conditions vary as much as your imagination. A filter may work fine at room temperature but it may fail before it reaches the boiling point of water.  Also, if the pressure is too high or the fluid is too thick, the filter element could blow out.

  • What is the temperature of the fluid passing through the filter?
  • What is the pressure in the system? What is the pressure drop across the filter?
  • Is the liquid so thick that the filter media needs reinforcement?
  • What volume does the filter need to handle? You will probably need to test a sample.
  • Does the filter need to remove a steady, heavy stream of particles?
  • Are you trying to stop sand grains or something much smaller? Knowing particle size is critical and filter pore sizes are usually in microns.

4. Physical Connections
How will you attach the filter? Do you need fluid flow to stop when removing or disconnecting the filter?

Additional considerations 
There may be features you would like to see in a filter. These may even be critical needs.

  • Visual inspection
  • Regulatory compliance (FDA, USP, NSF)
  • Color coding by filter element pore size
  • And so on…

The internet plays an increasing role in sourcing commercial flow control parts. Use these tips to create a list of the features your in-line filter requires:

  • Define the type of separation you want from the filter
  • Identify the potential chemicals that the filter will be exposed to
  • Figure out all of the environmental conditions where you will use the filter
  • Evaluate the type of physical connections required for the filter

Looking for the right in-line filter does not need to be a long search full of dead ends. Save that effort for your application.

Look for our upcoming blog article for a discussion of mesh and microns:

How to Choose an In-line Filter – Mesh and Particle Size

What kinds of problems have you had trying to figure out the list of features your in-line filter needs? Tell me your story.

Still have questions about how to select the right in-line filter for your application? If so, send me an email –


Steven C. Williams headshot March, 2018.

About the author
Steven C. Williams, BS, is the technical writer and an inbound marketing specialist at Industrial Specialties Manufacturing (ISM), an ISO 9001-2015 supplier of miniature pneumatic, vacuum and fluid circuitry components to OEM's and distributors all over the world. He writes on technical topics related to miniature pneumatic and fluidic components as well as topics of general interest at ISM.       
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