Better pump control ensures skid accuracy
9 Nov 2021
When a specialist industrial skid builder sought to enhance accuracy and sustainability, it determined better pump control was vital and sought the help of Watson-Marlow...
The need to build skids is commonplace in applications such as polymer dosing – used to eliminate unwanted solid particles from liquid streams in sectors that include water and wastewater, mining, pharmaceutical, pulp and paper, and beverage.
But in an age when not only competitive edge but also regulatory and consumer pressure for more sustainable products is paramount, customers will seek a level of control that helps reduce polymer consumption, increase cake dryness, improve solids recovery, lower energy consumption and reduce maintenance costs.
As a renowned skid builder PolyGhost, based in the Caribbean island of Puerto Rico, acknowldges both peristaltic and diaphragm pump types can offer 100% dosing accuracy. However the firm maintains, if a pump needs additional components in order to operate correctly, such as the required by a diaphragm pump, dosing accuracy will start to decrease because of operational and mechanical variables.
Among the objectives was enhanced process control. For this it turned to Watson-Marlow Fluid Technology Group Qdos peristaltic metering pumps.
Its solution, unveiled recently, was a patented technology that continuously blends multiple chemicals, additives and liquid polymers inside a mechanical mixing chamber.
A key selling point was that these products do not require regular and expensive maintenance, and deliver high levels of process control. So, when clients need full control of polymer blending for applications such as the optimisation of sludge dewatering or separation processes, PolyGhost solutions meet these requirements by integrating the company’s PolySurf+ software with Qdos Universal pumps.
As part of a typical sequence for a PolyGhost skid, once the operator verifies that the water control valve is open and the pump dose rate has been set, the start button is pushed. Here, the dilution water solenoid valve receives a PLC signal to open.
This dilution water starts flowing through the system, with flow meter readings sent back to the PLC. If water flow is passing through the system correctly, after 20 seconds the PLC sends a signal to start the polymer blending system. A further 15 seconds later, the PLC sends a signal to the Qdos Universal pump to begin dosing at the specified rate.
PolyGhost uses the input/output connections on the interface of the Qdos Universal+ to control the pump from the panel of the polymer blending system, allowing run/stop commands and flow rate adjustment.
Qdos users can determine the level of control as the pumps come in five variants: from manual (manual control via keypad and display for basic tasks), to the Universal+ (ultimate flexibility for automatic and manual control with five configurable outputs) chosen by PolyGhost.
The Universal+ is proving increasingly popular as it offers remote feedback capability, informing users of its speed via a 4-20 mA output.
Accuracy ensures savings
Typically, the required accuracy of PolyGhost applications is between 98 and 100%. If the customer is deploying diaphragm pumps, PolyGhost says it can optimise the user’s process with Qdos units, guaranteeing savings of at least 30% in polymer consumption, and sometimes up to 65%.
Control capability provided by Qdos pumps reduces chemical use through higher accuracy metering: Users can achieve accuracy of ±1%, alongside repeatability (precision) of ±0.5% and turndown up to 20,000:1. In some cases, claims Polyghost, clients achieve payback in a matter of months and it is also possible to avert any potential for under-dosing, which is hugely significant in sectors such as water and wastewater treatment.
