What Are Common Types of Strainers for Water Treatment Applications?

July 6, 2021

Breaking down types of strainers & their optimal applications

About the author:

Mark Ligon is the marketing manager at Commercial Filtration Supply. Ligon's experience in industrial filtration has provided valuable relationships with suppliers, manufacturers and vertical resources online. CFS has more than a decade of experience providing name brand/quality products to the industrial filtration market. Ligon can be reached at [email protected] or 855.236.0467.

When clean water is needed, strainers can be used to achieve highly effective filtration. Strainers can remove contaminants of many different sizes, from small organic material to large debris. While they have many purposes in the filtration process, strainers most often serve as pre-filters, removing particles from water before they make their way to equipment downstream, where clogs or damage could occur.

What Are Common Types of Strainers for Water Treatment?

The strainers most commonly used in the water treatment process include basket strainers and duplex strainers, as well as self-cleaning and temporary strainers. The type of strainer best-suited for an application is determined by the type of contaminants that needs to be removed, the configuration of the system, and the amount of downtime acceptable for cleaning, maintenance and replacement.

Basket Strainers

Many water treatment applications utilize basket strainers. They are typically installed in horizontal pipeline configurations and located upstream from valves, machinery and other heavy equipment. Basket strainers serve as an effective pre-filter, keeping the machinery down the line free of debris and damage. This cuts down on maintenance costs, as well as replacement costs and downtime in the future. Basket strainers are a great solution where ultra-fine filtration is needed, but high pressure must be maintained.

Basket strainers are usually made of stainless steel, which not only ensures their durability but also makes them easy to clean. Their basket shape creates a large filter area, and they have a high capacity of holding contaminants. Though single-basket strainers are easy to remove and clean, double and multi-cylinder configurations are available as well, cutting down on regular processing downtime. Mesh size should be selected based on the size of contaminants that need to be removed, making basket strainers an effective and customizable filtration tool in water treatment applications.

Duplex Strainers

When a water treatment system is running around the clock, even the smallest shutdown can have a huge impact on productivity. In addition, frequent changes in water pressure could impact other steps to the treatment process. Duplex strainers provide the same level of filtration as single strainers but do not require a system to be regularly shut down for cleaning. The double/duplex strainer configuration allows workers to simply swap out strainers when one becomes full. The system can be functioning while the switch is made, and water pressure is only minimally affected during the changeover. Select a duplex strainer that provides adequate filtration needed to ensure that the suspended contaminants commonly found in the water supply are being effectively removed.

Self-Cleaning Strainers

While the benefits of duplex strainers are obvious, unfortunately, not all system designs can accommodate more than one strainer. In these configurations, self-cleaning strainers may be the best option. They provide continuous flow and little pressure change through a motorized filtration device. Water flows upward toward the filter, which blocks suspended particles from passing through. These particles are then pushed downward, where they are collected. When pressure drops to a set point, contaminants are automatically eliminated through the flush valve. No shutdowns are required, as a backwash system is utilized to continually clean the filter and remove debris.

Self-cleaning strainers are highly effective at filtering water at all contamination levels, from freshwater to brackish water, and even salt water. They also provide a high level of filtration for liquids with a higher viscosity. In water treatment applications, they may be used both as pre-filters and secondary filters.


Temporary Strainers

While basket strainers, duplex strainers and even self-cleaning strainers are all installed permanently, aside from the occasional removal for maintenance, some filtration needs are only temporary. Before a water treatment system starts processing water for the first time, or when a treatment system has been shut down for an extended period of time, it is not uncommon for debris to make its way into the pipeline. Metal particles, for instance, may remain from installation, or sludge could have developed in the system while it was not running. If a water treatment system is started up with these contaminants present, the strainers could be overloaded, and pressure and productivity could be negatively affected.

Temporary strainers are installed to remove coarse debris and unwanted contaminants for a set amount of time. Once the system itself is free of debris, the temporary strainer can be removed and stored for a later date. In its place, a spacer washer is installed. These strainers utilize either flat disks or cone-shaped baskets to remove contaminants and come in a variety of mesh sizes. The cone-shaped strainers provide a larger filtration area; however, temporary strainers with the flat disk design are an effective option when the baskets cannot be installed.

Using Strainers in Water Treatment Applications

Clean water is needed for so many reasons, from providing freshwater to homes and businesses to power generation plants. In most water treatment applications, a number of different filtration methods may be needed. Strainers provide highly effective filtration and often serve as the first line of defense in the water treatment process, keeping contaminants out of machinery and equipment down the line.

Basket strainers have a high holding capacity without a change in pressure, and their stainless steel design makes them easy to clean. When a system shutdown is not possible, consider a duplex or self-cleaning strainer. Duplex strainers can be rotated out easily, without the need to shut the system down completely. Self-cleaning strainers are motorized, pushing waste downward, where it will be automatically flushed out. Finally, temporary strainers are utilized prior to the water treatment process starting, flushing out debris from manufacturing and installation, or removing debris that has remained within the pipeline during an extended shut down.

Each of these strainers comes in a variety of mesh sizes and should be selected based on the type of filtration needed. Water treatment systems are only as effective as the filtration techniques they utilize. Working with a filtration specialist to determine the best strainer for all applications is highly recommended.

About the Author

Mark Ligon