Water Connections: Chopper Pump 'Chips In' to Solve Clogging Problem

Aug. 11, 2020
Pumping solution dewaters sumps where pump plugging and maintenance problems plagued pulp mill

The Harmac Pulp Mill in Nanaimo, British Columbia, has found a pumping solution to dewater sumps where chips tend to cause pump plugging and maintenance problems. This kraft pulp mill produces approximately 365,000 tons of pulp per year. The pulp is produced from wood chips delivered by 50–60 trucks on an average day and over 100 trucks on a busy day. All these wood chips are unloaded from trucks using a hydraulic truck tilt system that dumps the chips into a below-grade conveyor system.

The wood chips and debris that escape the conveyor system accumulate on the floor of the below-grade vault and are hosed weekly into a sump which is then pumped elsewhere.

The Problem

Previously this chip receiving sump was pumped out with a self-priming pump that experienced plugging in the suction and discharge pipelines and in the pump on a weekly basis, leading to regular downtime and headaches for the mill. For many years the existing self-priming sump pump struggled to pump without clogging the check valve or plugging the line. This caused weekly frustration and downtime for the mill.

The Solution

In late 2014 a Vaughan Vertical Wet Well model V3L 3” discharge Chopper Pump was installed in place of the existing self-primer. Vaughan Chopper Pumps are centrifugal pumps with the unique ability to chop and condition incoming solids as part of the pumping action. The patented chopping action of the pump enables it to easily handle the fibrous wood chips and other debris that is washed into the sump.

The vertical wet well configuration of the pump provides the added advantage of eliminating suction piping while still keeping the motor and wiring out of the pit. Another important consideration for the installation includes a separate water line to the sump, which provides agitation and prevents chip stratification during pit pumpdown.

The Results

Since installing this Vaughan Chopper pump with sump agitation four years ago, downtime associated with this application is typically only caused by clean-up crews who unknowingly fill the sump with unpumpable dry chips. When this occurs it is easily addressed, leaving the mill employees more time and energy to focus on production. The mill staff no longer have to unplug the pump and pipelines on a weekly basis, an improvement that saves thousands of dollars per year. As there are no longer any issues with cleaning of the floor area around the conveyors, the pulp mill is saving time and money and staff morale is improved. WT

@bio:Since 1960, Vaughan continues to offer chopper pumps, hydraulic mixing systems, screw centrifugal pumps and one-on-one analysis and support to make sure they work for every application, including agricultural, municipal and industrial. Learn more at chopperpumps.com.

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