In sand and aggregates operations, performance and profitability depend on the reliability of equipment. Managing process water, reclaim systems, and pit dewatering are essential to the success of a project. Efficient fluid handling can reduce downtime, lower energy costs and eliminate the need for double handling. However, many quarries report time and budget constraints that don’t allow for system improvements to be implemented in their sand and aggregate operations. By not investing in the downtime necessary to make system improvements, operations are forgoing process improvements, long term energy savings and best equipment selections to reduce maintenance costs.

Optimising pump systems

1. Oversized pumps

A range of submersible, centrifugal and vertical turbine pumps are used in aggregates applications, but are often poorly matched with the duty. This can be due to sites repurposing existing pumping equipment from other applications that result in pumping systems that are either extremely oversized or undersized to match what the customer is trying to achieve. Running an optimised pumping system for your application results in improved wear life and less power consumption.

Solution – Adjusting Pump Performance

Solutions to resolve over-capacity include adjusting the performance of an installed pump to match the process conditions by either changing the operating speed or trimming the pump impeller. An alternative solution is to replace the installed pump with a higher efficiency pump to reduce power demands.

Flow is proportional to speed so, for example, a 20% reduction in speed will lead to a 50% reduction in energy consumption and a 50% reduction in speed results in an 80% reduction. The Weir Minerals team of dewatering experts can provide a thorough review of the operational cost saving opportunities available and provide a plan on how these can be implemented to minimise operational downtime.

Solution – Electric vs Diesel Options

A second important consideration is evaluating the power generations options electric, diesel, or a combination of the two.

The Multiflo® LF pump, for example, can be supplied with diesel engines (T3 & T4F rated engine emissions) or electric motors drive options. The LF is engineered for efficiency with a proven, enclosed impeller design and leading-edge materials that dramatically reduce the total cost of ownership. These pump packages provide a dependable pumping solution with flow rates ranging from 100m³/h to 3,200m³/h and discharge heads of 10m to 210m.

2. Problem – Dirty Water

‘Dirty water’ is the name given to water with a percentage of abrasive suspended solids that are too high to be considered ‘clean’, but too low of a percentage to be classed as slurry. The introduction of, and subsequent wear from, abrasive suspended solids is one of the most common causes of premature failure in a dewatering pump. One of the most challenging things to plan for is an ‘up-set’ water quality condition that can be caused by seasonal weather events, unexpected landslide or subsidence into a pond or the introduction on foreign waste stream (i.e. Tailings)

Solution – Proper Pump Selection

Solutions to resolve accelerated pump wear issues include improving the process water quality to reduce the abrasive solids content in feed water. In the event this is not possible, the best option is to replace the installed pump with a pump better able to process increased solids concentrations, such as the Warman® DWU pump.

The Warman^® DWU pump is designed and constructed to handle percentages of abrasive suspended solids percentage in water whilst operating at high discharge head pressures to transport surface water from dams and ponds on site back to the washing circuit for recycling.