Strainers vs. Filters: How They Differ

Strainer & Filter Equipment Connected Together

Industrial strainers and filters are designed to remove unwanted particulates from a liquid or gas. The key difference between strainers and filters are the size of the particles they remove. Strainers typically remove larger particles that are visible in a liquid or gas, while filters remove contaminants that are often so small, they cannot be seen with the naked eye.

How Strainers and Filters are Similar

Several commonalities exist between filters (such as bag and cartridge) and strainers (such as these), and it’s understandable that the two may be confused. For instance, both are designed to remove suspended particles from a gas or liquid. By doing so, both filters and strainers protect downstream equipment from contaminants that could cause damage or diminish the quality of the final product. In addition, both strainers and filters can be configured in a duplex design, allowing for one filter or strainer to be cleaned while the other is still operational. While there are many similarities between the two, however, filters and strainers are not interchangeable.

How Strainers are Different from Filters

Stainless Steel Industrial Strainer

The purpose of a strainer is to remove larger, unwanted suspended particles from a liquid, primarily to protect downstream equipment, like pumps, from damage. They come in a variety of shapes and sizes, depending on the application, but one feature is essential – strainers are designed for easy removal and cleaning. Quick cleaning requires less downtime for the equipment to ensure optimal functionality.

While strainers are used to remove larger particles, filters are used to remove smaller unwanted particles from both liquids and gasses. Filters are typically used when the liquid or gas passing through the system must be free of most contaminants, even those as small as a grain of sand. Many filters are reusable, while others must be replaced periodically.

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A general rule of thumb is that filters remove particles smaller than 40 microns, which are typically too small to see. Strainers, on the other hand, remove particles larger than 40 microns. Something this size would usually be visible with the naked eye. In some applications, it may be possible to use either a strainer or a filter, if the particles you wish to remove are between 38 and 177 microns.

Another key difference between filters and strainers is the pressure of the gas or liquid as it passes through the medium. Liquid passing through a strainer will likely not see a drop in pressure as it passes through. If there is a drop in pressure, however, it might indicate that the strainer needs to be cleaned or removed. On the contrary, liquid or gas passing through a filter will likely experience a noticeable drop in pressure.

Factors to Consider when Choosing a Strainer or Filter

When choosing whether to utilize a filter or a strainer, consider the following essential points:

     •  The type of liquid or gas

     •  Size and shape of particulates to be removed

     •  Whether the system can be shut down for cleaning and maintenance

     •  Flow rate and pressure

     •  Pipeline size and configuration

Size of Contaminants Determines Size of Mesh

When considering the size and shape of the particulates that you’ll need to remove, choose a mesh that is slightly smaller than what you’ll need. This will help to remove broken down contaminants as well as those that could have the ability to deform to slip through the mesh. It may seem like it would make sense to choose a strainer or filter with a much finer mesh than needed, but the finer the strainer or filter, the more frequently it will need to be cleaned.

Frequency of Maintenance Determines Configuration

Industrial Single Housing Filtration System

If your system cannot manage frequent shut downs for cleaning and maintenance, you may want to consider a duplex housing. This configuration will allow you to remove and clean, or replace one filter or strainer while the other can continue to function. In a single configuration, the entire system will need to be turned off and depressurized before maintenance can be done.

Check out our selection of Multi-Cartridge Filter Housings here.

For Multi-Bag Filter Housings, go here.

Finally, if you’re interested in Duplex Strainers, go to this page here.

Flow Rate and Pressure Affect Choice of Strainer or Filter

Flow rate and pressure is another key factor when choosing a strainer or filter. Because filters do impact both flow rate and pressure at higher rates than strainers, those using high flow systems may face more setbacks with filters. However, high flow liquid filtration systems exist and may be an option for your system. To learn more, read our post on the advantages to high flow liquid filtration.

Additionally, the size and configuration of your pipeline is important also. Some strainers and filters can only be installed horizontally, while others function best in a vertical housing.

The Differences between Strainers and Filters

Both filters and strainers work to remove unwanted particles from liquids and gasses. The primary difference between the two is the size of the particles you need to remove. Strainers are commonly used to remove larger particles, those visible to the naked eye, so that equipment downstream can work at optimal functionality. Filters, on the other hand, are more typically used to remove smaller particles, those that can’t be seen with the naked eye. Contact Commercial Filtration Supply to learn more about which of these useful products would be best for your specific application.