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Modular wash plant makes splashdown in Dubbo sand quarry

Dubbo Sands is a privately owned and operated quarry business that was formed by owners Mardi and Graham Colbran in 2003.

The company is a leading producer of sand and gravel, serving the central west of New South Wales. It offers a range of products including washed all in sand, washed coarse sand, washed fine sand and washed riverstone in many sizes.

Terex Washing Systems (TWS), the eastern Australian distributor Mineral Washing Systems (MWS) and the customer Dubbo Sands worked together to devise a solution to meet site-specific needs.{{image2-A:R-w:350}}

After careful analysis of the feed material it was identified that a portion of the Dubbo Sands feed contained high levels of silt, therefore demanding a system that would deal with this in one pass. With its old wash plant Dubbo Sands often had to wash this difficult material twice.

MWS proposed the TWS AggreSand 165, with a three-deck aggregate screen and a single sand plant.

The AggreSand 165 provides a fully integrated feeding, screening and sand washing solution on one modular chassis.

The entire wash plant, including the pre-wash system, was transported to Australia from the TWS factory in Dungannon, Northern Ireland, in just seven 13m shipping containers.

The modular, pre-wired and pre-plumbed concept of the AggreSand 165 allowed for rapid deployment once it was delivered to the site. The plant was fully erected and commissioned within a matter of days.

FEED SYSTEM
Dubbo Sands wanted to blend varying feed materials from its site, so a dual feeder system was proposed. The feeders both have a 12m³ capacity and were configured so the two grades of feed material could be blended at different rates before being conveyed to the wash plant. Both 4m feeders are powered from one electric hydraulic power pack and both have remote control hydraulic tipping grids.

The blended feed material is delivered to the 16’ x 5’ screen by a heavy-duty inclined feed conveyor fitted with a 1000mm belt. At the head of the conveyor an integrated wash box gives the material an all-important
pre-soak to pre-condition before going on to the screen.

AGGREGATE RINSING SCREEN
The two-bearing 16’ x 5’ screen provides a true 80ft² screening area on each deck. The high quality polyurethane modular deck adds excellent screening and wear qualities to the aggregate rinsing screen.

The isolated spray bars being fitted with polyurethane gators means the spray bars remain static as the screen vibrates.

The screen is powered by a 15kW electric motor and has a 10mm throw. For access around the screen, there are walkways on all four sides and a rolling chute to allow easy screen/module access. The inclined feed conveyor is fitted with hydraulic rams that allow the conveyor to be raised above the screen for even greater access.

The top and bottom deck materials are stockpiled by the AggreSand’s integrated 9m stockpiling conveyors. These conveyors each have a stockpiling capacity of 150m³. The conveyors are powered by an electric motor and have a 650mm wide belt.

PRE-WASH SYSTEM {{image3-A:L-w:350}}The pre-wash system is one of the first of its kind in Australia. The polyurethane in the bottom deck of the aggregate screen is split between one-third and two-third sections, with 1mm and 4mm polyurethane modules respectively.

The catch box under the screen is specially designed to capture and separate the two grades of sand (0-1mm and 0-4mm).

The fine material that passes through the 1mm section of the screen is safely collected and piped to the pre-wash conical sump tank.

The conical sump is designed to initially float off any light material (silt), with the heavier material dropping to the bottom of the sloped wall tank.

It is also designed to enable regulation of incoming water and solids flowing in varying conditions, without the loss of useful fines. A rubber-lined centrifugal pump then transfers the material from the bottom of the tank to a cyclone/separator.

The separator gives a secondary cleansing of the sand and removes more material below 75 micron and sends it off to the Dubbo Sands dirty water management system.

The beauty of the separator is that it can cope with varying levels of silt due to a discharge regulator that ensures a constant underflow density. This ability to deal with varying silt levels was Dubbo Sands’ number one specification for the entire plant.

The adjustable air bleed-off valve enables vacuum control that affects the moisture content of underflow material.

The overflow material is directed towards the water management system while the underflow is piped to the AggreSand’s
sand plant.

SAND PLANT
The pre-washed sand enters the AggreSand’s sump tank and is pumped by a rubber-lined centrifugal pump to a cyclone, to remove any remaining silt (<75 micron) before being dewatered on a 12’ x 5’ dewatering screen.

The dewatering screen is producing sand below 12 per cent moisture, which eliminates the need for stockpile drainage.

This is a windfall for Dubbo Sands because demand is high for this quality concrete sand, which is instantly saleable and can be loaded onto a truck from the stockpiler belt. In addition, the plant is producing two washed aggregates from a 200 tonne per hour feed.

“We were delighted when Dubbo Sands selected MWS as its preferred supplier for the wash plant,” MWS sales manager Niall Donaghy said.

“The new plant is fully satisfying the customer’s aggregate washing needs. The aggregate screen is fitted with a 65mm top deck, a 22mm middle deck and the split 1mm/4mm bottom deck.

The 16’ x 5’ screen is producing two very clean aggregates, which are being used as drainage stone, landscaping stone and for concrete production.”

“The professionalism and dedication from the entire MWS team, starting with purchasing right through to commissioning, has been outstanding,” Dubbo Sands owners Mardi and Graham Colbran remarked.

“We feel that there is nothing else currently on the market that even comes close. Our AggreSand wash plant incorporates the pre-wash system that enables us to bring our sand into spec in just one pass, while producing clean-sized aggregates, giving us a very cost-effective operation. Everyone worked extremely hard to pull this together, and we are positive ours will be the first of many hitting Australian shores.”

KNOWLEDGE, EXPERTISE {{image4-A:R-w:350}}MWS has more than 35 years of industry experience and is one of TWS’ leading distributors in Australia, providing cohesive solutions for all material and mineral washing needs.

The company has extensive product and application knowledge, which benefits clients throughout design, installation, commissioning and after sales support.

“MWS has grown from strength to strength, clearly demonstrating an acute understanding of the washing demands in Australia,” TWS sales manager Fergal McPhillips said.

“It has greatly increased market share and has expanded its business line for greater future growth within all washing segments such as speciality/recipe sands, concrete and building sands and in wash recycling. The recent launch of the AggreSand helped pave the way for helping to establish TWS as a market leader.”

OPEN DAY POSITIVES
Dubbo Sands hosted the first of several TWS international open day events in 2014 for prospective customers. Attendees were impressed with the plant, which was evident from some customer feedback.

One customer commented that the Aggresand was “very impressive and clearly an efficient unit”, while another stated he was “impressed by the modular system, with its quick set-up and ease of maintenance”.

A third customer added the open day was “extremely informative, presented by staff who were knowledgeable and experienced”.

“The open day proved to be another successful showcase for TWS,” McPhillips said.

“Reaction to the plant was exceptional and we received immediate orders as a result. The AggreSand 165 wash plant is continually proving to set TWS apart from other providers in the market and is revolutionising the wash plant market by introducing innovative solutions and continuing to serve our customers’ needs and demands around the world.”

The Colbrans said they were proud to be involved with TWS and MWS in hosting the first AggreSand 165 wash plant release in Australia.

“The open day was a huge success, with so many positive comments,” they said. “We know we made the right decision. The knowledge and expertise has been proven on the ground, with the team sent from Ireland, working alongside Niall, we have exactly what our quarry required and more.”

Source: Terex Washing Systems

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