Correctly sizing and selecting industrial, commercial or municipal filtration and strainers can reduce process downtime and maintenance time while improving product quality.

The Carotek Guide to Selecting Strainer and Filter Design explains filtration selection and sizing. When you need more help with your final selection, please contact us.

TYPES OF FILTRATION EQUIPMENT, FILTERS AND STRAINERS

Filtration Systems using filters and strainers share a similar function. They separate solids from fluids to remove unwanted contaminants and to protect processing equipment downstream. The primary difference between filters and strainers is the size of particulates they are designed to remove.

Filters often remove particulates measured in microns, while strainers remove larger particles that would be visible with the naked eye.

In order to understand how to size and select industrial, commercial or municipal filters and strainers, a general knowledge of the types of filtration on the market can be useful, and filters (filtration) and strainers should be considered separately.

Specification Requirements for Filtration

As previously stated, filtration of particulates that are not visible to the naked eye is generally the province of filters vs strainers.

Common Types of Filtration

Industrial filtration system products are often divided into surface filtration and depth filtration. Surface filters are generally used for higher concentrations of particles, while depth filters are used for lower concentrations. Surface filters are generally better suited for applications that require backwashing.

Filtration Comparison Guide

Each type of filter offers its own advantages.

Bag filtration systems consist of a filter housing and filter bags made of felt or fabric mesh, which are either sewn or welded. A bag filtration system is generally inexpensive and works well in a range of process conditions. Some bag housings are available with steam jackets. 

Cartridge filtration systems use modular filters in a housing, so this style generally offers a longer service life.

Automatic Self-cleaning filters offer tubular backwashing and mechanically cleaned technology for continuous flow, simplified maintenance and worry-free operation, saving labor and production down-time.

Filtration Size

When choosing the optimal filtration size for a filter, consider the smallest particle size that needs to be removed from the fluid. Pore size of a filter is measured in microns, so a 10-micron filter will remove particles as small as 10 microns. To reduce maintenance and improve efficiency, it’s important not to select a size that is much smaller than the particles to be removed.

Specification Requirements for Strainers

When particles that are visible to the naked eye need to be removed from a fluid, a strainer is often indicated.

Common Types of Strainers

Strainers are mechanical devices placed in-line with process piping to remove solids from a flowing liquid. Strainers can be cleaned and reused. Industrial strainers system products are available in a variety of styles including basket strainers, Y strainers, and temporary strainers. Additional types of strainers include back flushing, automatic self-cleaning, and special application strainers.

Strainers Comparison Guide

The ideal type of strainer depends on the filtration needs at that point in the industrial process as well as the direction of piping.

Basket strainers are a type of strainer used with horizontal piping, featuring a debris collection chamber and drain connection that must be located in the lowest possible position. Basket strainers can be either simplex or duplex strainers.

Simplex strainers are designed with a single in-line strainer basket.

Duplex strainers are designed with two strainer baskets so the flow can be switched to allow for one basket to be cleaned while not stopping the process flow.  They come in a variety of metallurgies and can be coated.

Y strainers are a type of strainer used with horizontal or vertical piping. They have a higher operating pressure range than basket strainers.

Temporary strainer, which are often cone shaped, are inserted with a flanged pipe spool. Temporary strainers are generally used for process startup.

Additional types of strainers include back flushing and automatic self-cleaning strainers to reduce manual maintenance, and special application strainers designed for unique characteristics, such as magnetic strainers to remove fine ferrous particles.

Strainers Size

Strainer mesh size selection is the key to efficient strainer operation. If the mesh is too large, the strainer will fail to remove some particulates. Too small and the strainer may clog or require more frequent cleaning.

When choosing the right strainer mesh size, a higher number indicates that smaller particles will be removed. Mesh size measures the number of openings in a single linear inch of mesh, so a higher number indicates a finer mesh.

Factors for Sizing and Selecting a Filter or Strainer

Although a filter or a strainer may be more suitable depending on the application, the general criteria for filtration sizing and selection are generally the same as the criteria for strainer sizing and selection.

Pipe size. The strainer or filter should be sized to match the existing pipe. In addition, pipe configuration (horizontal or vertical piping, or right angle) affects which type of industrial filtration would be a best fit.

Flow rate. Maximum flow must be accommodated. Minimum flow is important for backwashing filters.

Temperature and pressure range. Filters are always rated for maximum pressure. Minimum pressure comes into play primarily for automatic, self-cleaning filters. Generally, a Y strainer rather than basket strainer is used for high pressure over 6000 psi.

Particle size and characteristics. Filter mesh is described with a mesh number (number of openings per inch), mesh size, and strand diameter that affect the size of particles collected.

Maintenance. If the line cannot be shut down, a duplex strainer may be needed so the flow can be switched when a basket becomes full. For some applications, a self-cleaning filter may be suitable to reduce the need to stop flow or disassemble piping.

Batch or continuous process. If the process operates for long periods without stopping, continuous filtration might be needed.

Material requirements. Often the filter or strainer material is specified as the same as the pipeline requirements, to ensure that it can handle the materials as well as ensure the same coefficient of expansion. If the filtration material is hazardous reactive, it may require specialized media.

Filtration sizing and selection depends on the properties of the material and the contaminants (or byproducts) that are being removed, as well as process needs. The ideal filtration solution also depends on whether automatic cleaning is necessary, and also whether the process can be interrupted to change or clean filters. Knowing how to size and select commercial filters and strainers is crucial to protect downstream equipment from damage due to contamination.

Carotek is a recognized leading supplier, service center, and maintenance facility for industrial, commercial and municipal filtration and strainers. Carotek offers extensive local product inventory, expertise, and support for a range of filters and strainers. We are the authorized distributor for Eaton Filtration.

Contact Carotek for expert selection assistance or browse our selection of filters and strainers to find the right fit for your application.

Download the PDF of our Guide to Selecting Strainer and Filtration Systems

Filtration & Strainer FAQs

How to select pipe filters and strainers in piping systems?

In order to select pipe filters and strainers in piping systems, it’s important to know the characteristics of the pipeline, process, and materials. The first step is to understand that a strainer is most often used for larger particles that can be seen with the naked eye, while a filter is used for smaller particles measured in microns.

How to select a basket strainer?

To select a basket strainer, first consider the filter housing. You will need to keep in mind where you need to place the inlet and outlet, the connection type needed, and the optimal sealing material type for application. Other factors to keep in mind include:

• Flow rate
• Temperature and pressure range (Basket strainers are suitable for lower pressures under 6000 psi.)
• Particle size and characteristics, which will determine your filter mesh size
• Batch or continuous process
• Material requirements

Based on your maintenance needs, a simplex or duplex strainer may be the best solution. Duplex strainers, which are available in a variety of metallurgies, are designed with two strainer baskets so the flow can be switched. In this way, one basket can be cleaned while the process continues to flow.

What is a strainer in piping?

When you see a strainer in piping diagrams, the purpose of the strainer is to stop small solid particles from traveling downstream with the fluid. A pipeline strainer traps particles that are smaller than the holes in its mesh, preventing damage to process equipment.