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Pump Supplies Install New Dewatering and Pumping Systems

First published in the December 2016 issue of Quarry Management as Reaching New Depths

Pump Supplies install higher capacity dewatering system at Aggregate Industries’ Torr Quarry, plus a new pumping system to improve discharge turbidity at Hanson UK’s Craig-Yr-Hesg Quarry

Quarries, by their very nature, are prone to nuisance water that must be removed regularly to maintain productivity and operations. So, when Aggregate Industries decided to expand one of their flagship quarries, a new dewatering system was needed both to manage the increased flow of water and to ensure any disruption to day-to-day operations would be kept to a minimum.

Torr Quarry

Covering 600 acres, Torr Quarry is one of the largest in the UK producing 6 million tonnes of construction aggregate per annum. Located 7km east of Shepton Mallet, the quarry is an important source of stone both locally and for supply to the south-east of England.

When planning permission was granted for the deepening of the quarry increasing its construction aggregate output to 8 million tonnes per annum, Aggregate Industries needed to source a pumping system that could successfully manage the extra incoming water flows.

Speaking about the decision to seek an additional pumping system, Steve Nice, the quarry-based development manager at Aggregate Industries, explained: ‘Constant water clearance from the quarry is critical to its day-to-day operations. As the quarry reaches new depths the additional groundwater and rainfall it is subjected to means it’s vitally important that we have the necessary system and equipment in place that not only ensures the quarry is efficiently dewatered, but also that it doesn’t hinder daily procedures.

‘There have also been a number of environmental issues that needed to be taken into consideration. With a lot of sediment at the bottom of the lagoon, we can’t simply pump directly into the local watercourse. Allowing time for the water to settle plays a key role in the process of moving the water from the quarry into the river Avon, and the chosen dewatering solution would have to take this into account.’

Having worked at Torr Quarry for many years, as well as at other Aggregates Industries sites, Pump Supplies were invited to quote for the scheme and subsequently chosen as the successful supplier.

Rob Bessant, contracts manager at Pump Supplies, commented: ‘We conducted a full site review to determine the required additional capacity and potential layout of the pumping system. With numerous needs for water within a quarry, it’s not just a case of implementing a system to remove nuisance water from site, but also process water. So we had to take this into consideration when specifying equipment.

‘We recommended the implementation of two large sumps that would be used as settlement lagoons, each one utilizing two Flygt 3240 290kW C-pumps, two Flygt BS2400 submersible pumps and one Flygt BS2250 drainage pump.

‘The Flygt C-pump has a double-channel impeller allowing excellent flow passing properties to maintain peak operational performance. The Flygt BS2400 provides excellent wear-resistance and is capable of operating in the toughest environments, while the Flygt BS2250 pump has a high flow capacity, excellent for dewatering quarries.

‘The Flygt pumps have proven reliability in arduous industries such as quarrying and we felt this design would offer the best combination of wear and high efficiency. In addition, the settlement lagoons would allow the water to clear, ensuring all environmental regulations would be met.’

Mr Bessant continued: ‘To meet the environmental challenge and ensure sediment would not be pumped into the watercourse, and to maximize the efficiency of the pumping system, the Flygt pumps were floated on tailor-made pontoons. This allows the settled water to be pumped straight into the local watercourse. The advantage of using a pontoon to float the effluent pump is thathe performance of the pump.’

Aggregate Industries’ Steve Nice concluded: ‘We are delighted with Pump Supplies’ innovative approach to our dewatering and pumping needs during this expansion. The bespoke solution utilizing effective and efficient Flygt pumping equipment has ensured we can now reach new quarry depths whilst still maintaining peak operational levels.’

Founded in 1982, Pump Supplies Ltd are one of the leading suppliers of submersible pumps into the UK quarrying market. Operating out of five strategically located depots, the business specializes in all aspects of submersible pumps, with vast hire fleet that includes popular drainage pump models such as the Flygt 2125, 2151, 2250 and 2400, among others.

The company also offers full service and repair facilities through its depot network or on-site service teams, and has vast stocks of pumps up to 90kW supported by all relevant accessories, including pipework and monitoring and control equipment. 

Craig-Yr-Hesg Quarry

Another recent contract has seen Pump Supplies working closely with Hanson UK to design, install and maintain a pumping system utilizing the company’s monitoring and control support at Craig-Yr-Hesg Quarry, near Pontypridd, in South Wales. The system is designed to assist and speed up the discharge process and, most importantly, improve the clarity of the water discharged from the site.

The site drainage system originally utilized six settlement lagoons with a gravity weir system, but working with Pumps Supplies the on-site team designed and installed a pumped system using a slightly modified construction with eight lagoons. The overall process involves collection and settlement into lagoons through controlled pumped discharge from two attenuation lagoons to the six settlement lagoons prior to gravity weir discharge to the river Taff, thereby maintaining 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 discharge turbidity are all designed to be monitored and logged via a built-in facility that runs the system either in a variable automated mode or at a fixed mode rate.

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

The pumps are coupled to fusion-welded pipework incorporating flocculent injectors that 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.

In addition, 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 also installed to provide a pleasant working environment. A backup 65kVA silenced generator set with an AMF panel keeps the system active during power outages.

In auto-mode, a 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’s 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 24h 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 and continues to work closely with Hanson to ensure the system operates at optimum efficiency at all times.

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