Anti-Ragging Technology Offers Sustainable Practice for Clearing Pump Clogs
Article Feature in Pumps & Systems Magazine – September 2023
By Industrial Flow Solutions Business Development Manager – Municipal Brad Hitselberger, & Technical Support Manager Jordan Boone
The United States Customs and Border Patrol facility in Rio Grande City, Texas, continually faced a serious challenge: chronic clogging was hampering pump operations at its wastewater lift station. Thousands of people pass through the border crossing every month. Some dispose of non-flushable items in the facility’s drains and toilets, causing towels, diapers, masks, rags, wipes, clothing and other materials to travel through the facility’s collection system. All this durable waste, combined with the fats, oils and grease (FOG) found in all such wastewater systems, compounded the problem.
The lift station’s pumps, tasked with keeping the wastewater moving, could not handle the volume of solids. Local operators repeatedly had to pull, clean and repair the pumps. Along with causing a recurring safety risk for maintenance crews, the persistent clogging created a budget headache and impacted the facility’s overall operations.
Municipal wastewater operators everywhere frequently confront the same issues. Clogged pumps can negatively impact any wastewater facility, and by extension, any community. Overworked pumps and constant maintenance mean damaged pumps, decreased pump life and increased energy and labor costs.
Left unchecked, pump failure can lead to sewer overflows. Such disasters risk environmental damage, threaten public health and lead to severe regulatory penalties. Given the stakes, operators are keen to solve the clogging problem.
Traditional Remedies Prove Ineffective
For the Border Patrol’s lift station managers, the answer was to replace aging pump infrastructure with new pumps that incorporate a built-in shredding assembly into the pump impeller. The shredder technology built into the station’s submersible pumps reduces solids to minute particles. In theory, this should have solved the clogging problem for good.
In practice, although the shredder worked as intended, it created a new set of issues. Despite operating at a frequency of 60 hertz, velocity constraints in the low-flow system allowed the shredded material to remain in the discharge line instead of pushing it downstream at a flow rate that would prevent clogging.
The accumulation reverted back into the pump volute, and after cycling multiple times, fibrous material clogged the eye of the impeller by wrapping around the cutter bar shaft. Operators found they still frequently had to pull and de-clog the impeller to avoid sanitary sewer overflows (SSO) into the station.
Most pump designs are susceptible to clogging or ragging:
Vortex impellers minimize clogging by creating a swirling vortex that allows solids to pass through, but they clog when fibrous material becomes entangled around the impeller’s leading edges. Over time, these obstructions can accumulate, reducing the impeller’s ability to handle solids.
Recessed impellers within the pump casing also pass through fluids with high concentrations of solids and slurries by creating a vortex effect. In these units, clogging occurs in the vane passage area when excessive solids or debris obstruct the flow.
Semi-open impellers have partially open vanes that pass fluids with moderately sized solids. These impellers clog when fibrous material catches on the vane edges and the accumulation restricts the passage of solids.
Closed impellers have narrow gaps between solid vanes, primarily designed for clean liquids without solids. However, clogging can still occur when debris and fibrous material accumulates within the clearances to impede fluid flow.
Cutter impellers are equipped with sharp blades or teeth to cut or chop fibrous material, effectively macerating solids. However, clogging can occur if the cutter bars are not properly maintained, become entangled or are dulled by continuous operation.
Macerators and shredders have other problems that underscore the advantage of keeping larger solids intact. Microparticles can pass through screens to collect downstream where processing equipment is not designed to handle large-diameter aggregates, causing more clogging.
Variable frequency drives (VFDs) were developed to alleviate the pump failure caused by clogs by allowing pumps to reverse upon startup or at a high-current set point. This may treat the effects of clogging problems, but it does not address the underlying causes. Rather than passing through, fibrous material also reverses into the pump volute to cause more clogging. Furthermore, running at reduced voltage until a high set-point is reached means clogs are undetectable until they are unmanageable.
Comprehensive Solutions Using Smart Technology
The Border Patrol eventually solved their lift station woes by adopting an anti-ragging technology that combines elements of traditional clog prevention with smart monitoring capabilities.
Anti-ragging technology offers a proactive approach to pump monitoring by detecting potential issues at the first sign of clogging, enabling early resolution and clearing of any potential blockage. With older systems, pumps typically slow when clogged and then speed up to free the material. This approach may work for a while, but experienced operators know it eventually fails.
Anti-ragging systems incorporate real-time monitoring of a pump’s torque profile at variable settings lower than the full load amperage (FLA). For example, the Border Patrol’s 3-horsepower submersible pump was set to operate at 2.7 amps. When solids initially catch on an impeller and slow the pump, the automated detection system stops the pump and briefly reverses flow instead of increasing power and over-speeding. This agitation loosens solid material before it forms a mass too large for the system to pass through.
Anti-ragging keeps solids whole, allowing them to be trapped downstream by screens. Pumps stay clean, solids are safely collected and microparticles are reduced. Another plus is an odor control function in some systems that runs pumps during low activity to avoid water stagnation and odor buildup.
Advanced systems use smart technology such as high-resolution touchscreens, cloud connectivity and software that logs many years of high-resolution data. Enhanced data collection helps operators monitor equipment efficiency, adjust settings, predict when maintenance is required and measure results—all from a centralized control center far from the toxic operating environment.
Adaptable anti-ragging technology streamlines installation and repairs, and it can be applied to multi-pump systems or any piece of rotating equipment, including motor pumps, blowers and mixers.
Brad Hitselberger is the business development manager—municipal with Industrial Flow Solutions. He is based in the U.S. and may be reached at [email protected] or 475-207-3806
Jordan Boone is the technical support manager with Industrial Flow Solutions. He is based in the U.S. and may be reached at [email protected] or 203-423-3946
For more information, please email IFS at [email protected] or call 860-631-3618 to speak to an expert.
