Articles & Case Studies

Addressing rag ingress of an inlet channel

Posted: Friday 26th June 2015

Pump blockages and rags are a significant barrier to energy and operational efficiencies at pump stations, causing unscheduled shut downs, safety hazards for operators, costly equipment repairs and increased power usage due to a decrease in the pumps’ hydraulic performance. Scottish Water observed these negative effects, caused by ingress of wipes and rags throughout Network Pump Stations and decided to install a proven, powerful solution in the form of two JWC International (JWCI) Channel Monster® Grinders at one of their problematic sites.

Mosside Sewage Pump Station has been in operation since 1961 and comprises three submersible pumps (duty/standby/assist) installed in the wet well to process a flow rate of 489 m3/hour. Over the last few years, Mosside has experienced a heavier than usual volume of rags and solids flowing into the station. This debris is especially problematic during heavy storms as the material would create a “raft” of solids which lead to blockages of the pumps during peak capacity periods and cause sewage to overflow in and around the pump station. This required the SW Operators to attend site on a regular basis to uplift and unblock the submersible pumps and also clean up the spillages - a time-consuming and unpleasant task.

The submersible pumps were originally protected by a coarse manually raked bar screen, yet the volume of rags was so heavy that Operators were concerned about the large amount of debris being manually removed from the Mosside Pump Station. They realized that the Bar Screen alone wouldn’t be enough to deal with this volume of debris so Scottish Water looked for an effective, proven solution that would immediately resolve the issues.

Scottish Water was familiar with JWCI product ranges, especially Muffin Monster® Channel Grinders as one unit had been successfully operating at another installation in the area since 2007. They appreciated the practical, reliable and economical solution that JWCI provided for that site and looked for a similar system to be installed at Mosside. Scottish Water contacted WGM Engineering (WGM), the Exclusive Distributor for JWCI in Scotland, to offer a solution that would resolve the issues with rag build-up and pump blockages caused by the ingress into the site. WGM undertook a thorough assessment and their design engineers recommended that the manual bar screen be removed, the levels of the wet well walls and access flooring be raised to accommodate high-capacity periods, and that two JWCI Channel Monsters be installed in the wet well, each on a guide rail system to facilitate easy installation.

The Channel Monster features a Rotating Screening Drum complete with 6mm Perforations which allow small particles through whilst capturing and feeding heavier rags and solids into a Dual Shafted Grinder. The Grinder conditions the solids contained within the flow into a uniform particle size to enable them to be easily pumped from site. Each Channel Grinder is sized to process the flow into the pump station which ensures all the submersible pumps are fully protected would no longer be subjected to blockages and associated equipment breakdowns.

Since the installation of the Dual Channel Monster System in March 2014, Mosside has seen a massive drop in the number of pump blockages which has freed up operators from having to attend site to undertake unnecessary uplifts and unblocking of the submersible pumps. Graham Black, the Area Manager for Scottish Water, expressed appreciation for the full-scale solution provided by JWCI and WGM;

“The JWCI Channel Grinders have made a difference to both our operational and overtime costs, freeing up a lot of our operator time to concentrate on other sites. The Channel Monster Grinders have taken away the fear of being called to Mosside time and time again.”

In addition to the reduction in unscheduled maintenance, the installation of the Channel Monsters has allowed Scottish Water to cancel other planned Capital Investments downstream in its Catchment Area which were no longer required due to the conditioning of the rags being pumped from Mosside Pump Station. The significant capital and cost-savings advantages, coupled with eliminating the necessity for operators to manually unblock the pumps and clean up raw sewage from overflows, made this project a success for everyone involved.

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August 2021

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