Washing: As it should be

In recent times the requirement to wash mineral reserves has become more frequent as operators tackle more difficult materials. With this upward trend set to continue equipment manufacturers have an important part to play in developing products which meet the evolving demands of the global industry. Peter Craven, Marketing & Sales Support Manager at CDE Global, outlines the approach taken by CDE Global in response to this challenge below.

There has always been a requirement to process difficult materials. The geology of a region plays a large part in influencing the processing system that is chosen and it is for this obvious reason that washing equipment has found its place in the market. When there is clay present in the material or high levels of 63 µm material a washing plant offers the best solution to ensure production of the highest quality sand and aggregates (Fig. 1).

When operators are faced with reserves which have variations in material quality they will obviously process the easiest material first. The selection of the appropriate system will be selected according to the nature of the material to be processed and the final products that are required to satisfy customer demands. As we have moved through the decades and quantities of this ‘easiest material’ have diminished the challenge for equipment manufacturers has been to continually develop and improve systems to ensure the more challenging materials can be efficiently processed.

One of the key developments of recent years has been the move to mobile equipment within the global construction materials sector. This began with the development of mobile crushing and dry screening systems which operators can easily move between different processing locations and also move around a single site in order to minimise the transport movements of other vehicles. The unique requirements of washing plants made this move to mobile a more challenging concept. Logic tells us that washing plants are restricted in their mobility due to the requirement for connection to an external water supply. The early attempts at mobile washing provided evidence of this and these plants were moved rarely – if at all.

Another short-coming in the development of the first washing plants described as mobile was the inability to successfully integrate the sand washing element with the washing screen. This required operators to purchase two separate items of equipment to deliver on the sand and aggregate production requirements. The result of these short-comings was that the uptake of these systems was limi­ted and the perception in the industry was that mobile washing plants had a problem – they weren’t mobile. Simply putting hydraulic tracks onto what was essentially a dry screen with the addition of a few spray bars was not a satisfactory solution.

The term “Mobile washing” had reached a point where it had become the evil that will not be spoken of due to flaws in existing systems. These systems did not fail because of limited demand or lack of promotion. They failed because of an assumption that the same design principles that apply to dry processing equipment can simply be copied when developing a mobile washing plant. This provided the motivation for the development of the M2500. Central to the creation of the M2500 was the integration of the sand washing element with the rinsing screen. The aim was to produce a mobile washing plant which offered feeding, aggregate washing, sand washing and stockpiling (Fig. 2) on a single chassis.

Another key issue was ensuring that the rinsing screen was suitable for the application and would stand up to the rigours of an aggregate screening process. The issue with previous mobile washing screens was that more often than not the spray bars were bolted to the screen box. This meant they were subject to extremely high stress levels which would ultimately result in failure. The M2500 eliminates this risk by offering a spray bar assembly which is completely independent of the screen box thus removing this risk of failure and ensuring the M2500 is designed for long term reliability and performance (Fig. 3).

By successfully integrating the ProGrade rinsing screen and the EvoWash sand washing plant onto the M2500 mobile washing has gained new momentum in recent years. The M2500 has quickly become established as the equipment of choice for operators in variety of industry sectors (Fig. 4) and has been employed on the processing of sand and gravel, crushed rock, dust washing, scalpings and construction and demolition waste recycling. In addition to this there are specific models available for mining applications. The success enjoyed by the M2500 since its introduction to the global market is evidence that with the correct design ethos, exis­ting processing systems can be substantially improved to offer the industry more efficient processing systems which help to improve product quality, reduce waste and meet the requirements of a fast changing industry.