Craig-Yr-Hesg Quarry

Pump Supplies has worked closely with customer Hanson to design and install a pumped system with monitoring and control support at its Craig-Yr-Hesg Quarry in Wales, speeding up the discharge process and improve the clarity of the site's discharged water.

The site drainage system utilised six settlement lagoons on a gravity weir system, but the Pump Supplies team aimed to design and install the pumped system using a slightly modified construction with eight lagoons. The overall process involves collection and settlement into lagoons. This is through controlled pumped discharge from two attenuation lagoons to the six settlement lagoons prior to gravity weir discharge to the river Taff, Pontypridd within Natural Resource Wales' consent parameters. A polymer flocculent agent is used to improve the settlement of the suspended solids prior to discharge.

Lagoon levels, pumped flows and discharged turbidity are all designed to be monitored and logged, with a built-in facility which runs the system in either a variable automated mode or at a fixed mode rate.

Pump Supplies installed two Flygt 13.5 kW 5100 hard iron submersible pump-sets which were suspended from rotating winch davits to allow for pump removal for maintenance and for regular settled silt clearance purposes – both of paramount importance for an efficient operation.

The pumps were coupled to fusion-welded pipework, incorporating flocculent injectors which feed the outfall baffle boxes via a network of sluice gates and valves. The operator can use these in conjunction with the pumped system to actively manage the discharge of site drainage water.

Pump Supplies converted a standard shipping container into a bespoke control room to house the twin pump control panel, control and monitoring analysers, data logging equipment and flocculent storage and dosing rigs. Heating and lighting were installed to provide a pleasant working environment. A back-up 65kva silent set generator with an AMF panel keeps the system active during power outages.

In auto-mode the Pulsar ultrasonic level controller provides start and stop signals to the ABB 550 variable frequency drives via the control PLC to dictate the process control. The PLC initiates the pumps and the flocculent dosing systems at predetermined lagoon levels and controls the pump speed and the flocculent dose rate proportional to the turbidity analyser 4-20mA output, thus allowing increased polymer contact time during high turbidity events.

Under normal operation only one pumping/dosing system is active on an alternate duty cycle. The start level is such that in dry conditions the attenuation lagoon water level will be kept to a minimum to provide maximum storage and contact time under wet conditions.

During storm conditions both pumps will be called to run if levels are high. The system is designed with a simple manual override function to allow the operator to control the pump speed and dose rates, or to set them at fixed rates, if required.

A web-based telemetry system provides real-time status information, including lagoon level, pump status, flow rates and turbidity. Programmed alarm notifications provide key personnel with SMS and email alerts on a range of incidents including power failure, pump failure, high level and high turbidity. Access to this information is available 24 hours a day, seven days a week via PC, laptop, tablet or smartphone.

Since the installation of the pumped system, the Pump Supplies team has implemented a maintenance schedule. The team continues to work closely with Hanson to ensure the system operates at optimum efficiency at all times.

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