Proper Check Valve Selection Will Reduce Maintenance and Roping in Wastewater Pumping Systems
Recent increases in flushed nondegradable items can mean serious problems, but using the right valves will help
Choosing the appropriate check valve for wastewater applications isn’t as simple as it used to be, as the amount and type of modern trash going through wastewater pipelines is steadily increasing and changing.
Today’s increased use of cleaning towels and wipes made from fabrics and plastic resins have treatment plant operators across the globe experiencing more and more difficulties and maintenance issues in pumps and piping systems. These pieces of fabric hang up and get caught on areas of restriction within a pipeline system, causing blockages as material builds up behind them. This is often referred to as roping, and it impedes system performance. The time and equipment needed to remove large clogs can be significant, resulting in high costs for repairs.
Avoiding roping in a system is best done by preventing material like nonflushable wipes or other no disintegrating materials from entering the system. However, controlling what the public flushes is an impossible task. What you can do is build your system to limit the potential snag points by using components that allow maximum flow with less system maintenance.
Check valves are a necessary part of any pumping system to prevent backflow and protect the pump and system from damaging surges and water hammer, but they can also be a common point of maintenance and restriction depending on the style. Swing check valves are commonly used in wastewater applications and can create a snag point due to their internal components that feature a hinged disc that swings off a seat to allow flow in one direction but blocks reverse flow by swinging back onto the valve seat when flow stops. When materials that don’t break down get caught on the internal components, not only can it create large clogs, it can prevent the valve from closing fully and functioning properly leading to water surges and hammering.
Instead of using high-maintenance, snag-prone swing check valves in wastewater applications where modern trash is anticipated, consider using ball check valves. Ball check valves like the ones designed and manufactured by Flomatic are anti-roping and self-cleaning valves with no sharp edges or snag points, which prevents clogging from nonflushable wipes and other trash. They have been proven in wastewater lift stations for decades with a simple and reliable design with the only moving part being a vulcanized metal ball.
When fluid is flowing through a pipeline, the ball is pushed out of the seat and stream into a separate chamber of the valve housing (Fig. 1). When the flow stops or reverses the ball rolls back by gravity into the seat, creating a fluid-tight seal (Fig. 2). The ball itself is buoyant, which greatly reduces friction and improves
The simple ball-in-seat design creates a smooth valve interior so particles and trash are able to flow through the valve without getting stuck. When under flow, the ball is constantly spinning which also contributes to keeping the valve free of debris, allowing it to work properly and stop reverse flow. The ball check valve has a self-cleaning seat as the vulcanized metal ball will seat on a new surface each time it operates pumping efficiency.
System engineers prefer valve designs offered by Flomatic, which feature a unique full-ported valve seat, allowing the ball to sit tightly without getting wedged into the valve seat. They are coated with a fusion-bonded NSF approved epoxy coating with no cast surfaces exposed, making them ideal for corrosive applications. They are available in a size range from 1 to 14 inches in ductile iron. Models and are also available in PVC and 316 stainless steel.
Aside from the anti-snagging design, ball check valves offer other advantages like easy repairs and flow efficiency. They are a simple design and require very little maintenance. Even if maintenance or cleaning is required, they are repairable in-line with a clean-out port making servicing very accessible, and they also utilize the standard AWWA flange-to-flange dimensions as swing check valves, so replacing is easy. The ball check valve body is also equipped with NPT tapped bosses for bypass piping or proximity switches to signal when the valves is open or closed. Due to all of these attributes, these valves are commonly used in submersible wastewater lift station applications.
So next time a check valve in your system needs replacing or is causing roping, consider the internal components of that valve and find out if a ball check valve is a better fit for your situation. It is extremely important to analyze the system dynamics to be sure that a ball check valve is a proper fit for your application, and when in doubt, contact a valve expert like Flomatic.
Flomatic Corporation is a longtime member of WEF, AWWA and SWPA.