Inline Filters for Miniature Flow Control Component Protection

Many systems use inline filters in combination with check valves or precision orifices for enhanced performance

Last updated: February 11, 2021

A rendered 3D model of an 8 5 1 6 0 series eighth inch hose barbed small plastic inline filter.
Figure 1 

IntroductionMiniature flow-control components such as inline filters are usually installed in air, gas, vacuum and fluid flow systems to perform very specific functions related to flow control. It is frequently useful to pair critical components in combinations that work well together.

The function of inline filters is often critical. Installing them helps ensure the proper function of other flow control components. This post looks specifically at some reasons why using inline filters in combination with check valves and precision orifices can improve productivity and reliability.

The 4 key things you should be thinking about when selecting a filter >>

Figure 1 is an 85160 series 1/8” hose barbed small plastic inline filter
Small inline filters like this one are compact, sturdy and compatible with a broad range of chemicals and gases. This makes them a great choice for capturing and retaining particles that could cause damage or malfunctions to other components.


A rendered 3D model of a 5 6 4 3 0 series quarter inch hose barbed small plastic inline filter.
Figure 2 

Filters as particulate protection for critical equipmentIt is quite common and almost a “best practice” to use small particulate capture in air, gases and fluid flows that are already quite clean. The reality is that normal application processes accumulate debris and particulates. Small, compact or miniature screen and sintered (polymer or metal) particulate filters are frequently placed in the flow to protect critical equipment as well as process fluid, air and gas purity.

Figure 2 is a 56430 small plastic inline filter
This inline filter is much like the other small plastic inline filters that ISM carries. In this case, the larger 1/4” barbed connectors allow a larger flow through the valve (about 0.156” diameter) while keeping the housing sturdy and the size compact.

Some critical equipment particle protection uses cases

  • Filtering ink to protect print heads in industrial marking and coding equipment
  • Protection against particulate contamination for miniature pneumatic systems
  • Fuel flow to carburetors, pumps, orifices and other sensitive components in small engines and heaters
A simplified color illustration of how surface filtration works.
Figure 3
Filter mesh provides 
surface filtration 

A quick note about small plastic inline filter capabilities
Micron rating is a key filter specification. Micron ratings are based on the filter’s ability to remove most particles larger than the rated size of the openings in the filter element. Filter mesh and filter screen capture particles on their surface (see figure 3). Depth or porous filters capture particles both on the filter element’s surface and within the filter material itself.

Find out more about filter mesh, microns and particle size >>

A quick note about small plastic inline filter construction
Small filters most commonly use a cone or cylinder-shaped filter element. This is because this shape helps maximize the surface area of the filter and provide the highest flow possible.

Also, most small plastic inline filters are assembled using sonic welding, also called ultrasonic plastic welding. Sonic welding creates a bond that is stronger than the plastic housing surrounding the weld. Besides adding sturdiness to the design, if a filter is made with FDA compliant materials, sonic welding avoids any issues with adhesives as potential contaminants.

Learn more about sonic welding at the Dukane Corporation website. Dukane is manufacturer of plastic welders for welding thermoplastic materials.

Contamination sources and effects
Sources of contamination and particulates:

  • Chemical by-products
  • Simple air compression
  • Assembly and maintenance
  • Manufacturing and storage debris in component parts
  • Contaminants introduced during the production of compressed air
  • Chemical and chemical by-product reactions with component surfaces

Find out more about material chemical compatibility >>

A rendered 3D model of an R I L series thread by hose barb precision orifice fitting.
Figure 4 

Precision orifices and flow efficiencyProperly functioning flow control usually requires specific air or fluid flow-rates and pressures to be productive. Precision orifices (flow restrictors) are frequently used to provide these metered flow rates and reduce downstream pressures. Orifices have the added advantage of requiring no intervention to regulate flow. For most flow-controlled systems to function properly though, there should be an even flow of air or liquid through the orifice or orifices used. One significant and usually preventable cause of irregular orifice flow is particle contamination.

Figure 4 is an RIL series precision orifice fitting
Filters added upstream of precision orifice fittings like this one help prevent clogging. ISM’s precision orifice selection also includes precision orifice options with integrated inline filters.

Contamination sources and effectsSources of contamination and particulates:

  • Chemical by-products
  • Chemical and chemical by-product reactions with component surfaces
  • Component wear debris
  • Component parts manufacture and storage debris
  • Assembly and maintenance
  • Simple air compression

How contamination and particulates can cause irregularities in orifice flow rates:

  • Particulates or particulate clumps can plug or block an orifice throat and stop flow
  • Buildup around an orifice throat can reduce the orifice diameter and reduce the flow rate


A rendered 3D model of an 8 5 1 6 0 quarter inch hose barbed small plastic inline filter.
Figure 5 

Inline filters and precision orificesPrecision orifices are critical to an extensive variety of air, gas and fluid flow control applications. When used with suitable filters, they provide highly cost effective precise and reliable flow control. This is because any precision orifice could clog without adequate filtration protection.

Using a separate small filter upstream of a precision orifice provides protective filtration that is easy to replace or service.

Figure 5 is an 85160 series 1/4” hose barbed small plastic inline filter
Like the 56430 small plastic inline filter, the larger 1/4” barbed connectors of this filter allow for a higher flow rate through the filter.

Check valves and efficiencyOrifices are not the only miniature flow control component that can have its performance degraded by particle contamination. Check valves and valves in general are vulnerable to the effects of particulate contamination because sealing surfaces need to remain relatively smooth and unchanged to prevent unintended and unwanted leakage.

How check valve performance can be affected by contamination effects on sealing surfaces:

  • Contamination can lead to corrosive erosion that may cause leaking
  • Contamination can cause sticking that results in erratic valve opening and closing
  • Contamination can prevent a check valve from sealing properly and cause leaking through the valve

Learn more about the basics of check valve function >>

A rendered 3D model of a C O P series compression by thread brass spring-loaded ball check valve.
Figure 6 

Inline filters and check valvesPlacing inline filters just upstream of check valves can help prevent buildup on sealing surfaces or corrosion that could compromise check valve function. The primary purpose of check valves is preventing unwanted backflow. In this case, the combination of check valves with upstream inline filters, also protects the filters from any potential negative effects of backflow.

Figure 6 is a COP series brass spring-loaded (spring assist) ball check valve
Filter added before check valve help prevent both buildup on the sealing surfaces and corrosion that can compromise check valve function.

Key takeawaysMost systems will function more efficiently and with lower maintenance costs when upstream inline filters provide contamination protection for check valves and precision orifices. Knowing this can make it easier to plan, design and maintain air, gas, vacuum and liquid flow control systems.

Issues of particulate contamination can potentially be a factor affecting every type of gas or fluid flow system. Understanding how it is possible to anticipate and minimize the effects of contamination on miniature precision orifice and check valve function can significantly enhance performance.

Adding inline filters can simplify maintenance, making it more reliable and predictable. This sort of planning can also reduce and possibly even eliminate the stress of unexpected additional maintenance and premature part failures.

Check out our next blog article where we look at material compatibility with some of the chemicals found in medical care settings:

New Resource: Medical Chemical Compatibility Chart >>

Have you had some difficulty maintaining the performance of precision orifices for one of your miniature flow control projects? How about check valves? Did the addition of in-line filters solve these problems? Did adding in-line filters increase efficiency or reliability or both? Help us by telling others about what you learned.

Have questions about inline filters as protection for flow control components? If so, send me an email – You can also ask questions or start a discussion about this using the comments section below.

Related blog posts
Precision Orifices (Flow Restrictors) for Flow Control >>

A typical plastic diaphragm check valve in both an exploded and a cross section view.
Figure 7 
Typical diaphragm check valve

Posts in our How to Choose an Inline Filter series:

Posts in our Check Valves series:


Steven C. Williams headshot March, 2018.

About the authorSteven C. Williams my LinkedIn profile link button.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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