Podcast: How should engineers choose between basket, backwash, and scraper strainers?

Industrial strainers are often specified by habit rather than by application need. In this episode of Great Question: A Manufacturing Podcast, Laura Davis, editor-in-chief of New Equipment Digest, examines when basket and backwash strainers make sense, and when automatic scraper strainers may offer a more reliable option for high-solids or variable-load environments. The discussion draws from an article by Del Williams for Acme Engineering Products, using real-world filtration scenarios to explore common specification pitfalls and practical considerations for engineers.

Below is an excerpt from the podcast:

This topic comes up a lot in water and process filtration across industries like wastewater treatment, power generation, food processing, and chemical manufacturing. And it matters, because the wrong strainer choice can quietly create maintenance headaches, reliability issues, and performance problems down the line.

So we’ll cover a few things. A common specification mistake engineers make, the real differences between basket strainers, backwash systems, and scraper strainers, and what to think about when choosing the right strainer for an application.

Ok, let's dive in.

Industrial strainers play a basic but critical role: removing suspended solids from liquids and slurries. That could be debris in cooling tower water, solids in wastewater, or contaminants in process fluids.

Consulting engineers are often involved in specifying these systems, especially on projects with bid specs or larger system-level decisions. And in many cases, familiar technologies become the default choice, such as basket strainers or backwash filters. The problem is that the default doesn’t always mean the best fit.

Traditional strainer designs work well in the right conditions, but they can struggle in applications with high solids loading, large debris, sticky materials, or variable operating conditions. That’s where alternative approaches, like automatic scraper strainers, tend to make more sense, even though they’re less commonly specified.

One of the most frequent issues is specifying a strainer without fully understanding the operating conditions. Which includes the type and size of solids, how much solid loading is expected, variability in flow rate and pressure, and how those conditions might change over time. If that information isn’t clear, it’s easy to end up with a system that looks fine on paper but underperforms in real-world operation.

For example, backwash strainers are sometimes specified for applications where solids are large, sticky, or difficult to dislodge. Those are exactly the conditions where backwash systems tend to struggle since they rely on pressure and flow to clean the screen. In those cases, mechanical cleaning approaches can be a better match.

To understand why, it helps to step back and look at the three main strainer types engineers typically consider—starting with the most basic option: basket strainers. Basket strainers are manual devices designed to remove large debris from a fluid stream. They’re common in water and process piping systems and do a good job protecting downstream equipment like pumps, valves, and meters. In continuous processes, duplex basket strainers are often used so one basket can be cleaned while the other stays online. But cleaning is manual, messy, and time-consuming. It involves isolating the chamber, opening the vessel, removing the clogged basket, cleaning it, and reinstalling it correctly. If cleaning is delayed—whether due to staffing limitations or competing priorities—both baskets can become clogged. That can lead to downtime or quality issues, often at the worst possible time. Basket strainers are inexpensive upfront, but they depend heavily on consistent human intervention.

To reduce that reliance on manual cleaning, many facilities move to a more automated option—backwash filtration systems. Backwash systems are more automated and are widely used in water filtration. They operate by allowing solids to accumulate on a screen until a pressure drop triggers a backwash cycle. During that cycle, flow reverses across part of the screen, dislodging solids and flushing them out through a drain. This approach works well when solids are relatively fine, solid loading is low, and good pressure is consistently available.

But backwash systems have limitations. They generally don’t perform well at low pressures, often below about 30 psi. They’re also less effective at removing larger or irregularly shaped solids, partly because the cleaning mechanism needs to sit very close to the screen. Backwash systems also tend to be more complex, requiring control valves, instrumentation, and sometimes external water sources. That complexity adds cost, installation effort, and more points of failure. Some manufacturers have addressed certain limitations with designs that operate at lower differential pressures and use process fluid for cleaning instead of external water. Those design choices can reduce water use and wear—but the core limitations of backwashing still apply in high-solids environments.

About the Podcast
Great Question: A Manufacturing Podcast offers news and information for the people who make, store and move things and those who manage and maintain the facilities where that work gets done. Manufacturers from chemical producers to automakers to machine shops can listen for critical insights into the technologies, economic conditions and best practices that can influence how to best run facilities to reach operational excellence.

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