To install or not to install – the question with perforated plate screens

With advancing screen technologies, utilities are working to find ways to use this technology for better capture efficiencies. Most often, the newer technology is some type of perforated plate band style screen, which presents a host of problems such as overtopping the structure, failure of screen components due to high velocities, failure to remove large debris, and high channel velocities resulting in significant carry through.

Because of this, maintenance becomes such a chore that utilities choose to replace the screen long before its end of expected life. But why do these screens fail when they’re the newer advanced screening technology?

In the Texas WET Tech Talk Issue 6, Garver Director of Water Services Jeff Sober’s article “For better or for worse: Installing a perforated plate screen – is this the best option for fine screening at an existing headworks?” discusses how this could be happening. And the main culprit? Forgoing key design criteria during headworks design. For instance, perforated plate screens are often installed in existing channels and retrofitted without confirming the full range of through screen velocities, which is one of five key design criteria for successful fine screens.

When the five key design criteria aren’t considered, utilities face challenges with screen installations, particularly for retrofits. And for Garver, these criteria are the basis for all our headworks and screening designs. Because, we know that their consideration during design can be the difference between success and a constant headache for operators.

Ultimately, Sober's article determines that while fine screening and perforated plates provide a better capture efficiency and more removal, they may not be the best solution for a retrofit. When the five key design criteria are considered, finding the right screen for your facility is much more successful.

Want to learn more about fine screens and how the five key design criteria can affect your screening decisions? Please contact Jeff Sober, PE, at JLSober@GarverUSA.com.