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The solid choice for hydrovac slurry separation

With 12 sets of its new GN Hydrovac Slurry Systems already being used successfully in the US and Canada, GN says it is “definitely a cost-effective choice”.

Hydrovac is a process that creates a slurry mixture of liquid with high solids content, approximately 60 per cent liquid and 40 per cent solids. Unlike conventional excavation, hydrovac excavation does not separate soil horizons; instead, it mobilises potential contaminants through the excavation addition of water (solvent) and agitation.

A unique procedure

In cooperation with a US client, GN Solids Control developed the first hydrovac slurry treatment system in the US three years ago. After witnessing the proven success, the client purchased another nine systems as the business grew, and another Canadian client purchased two systems on referral.

All GN’s systems have been kept in the original basic concept and been continuously upgraded in their final details in order to perform better.

GN says there are some different options in the market already, with sediment being the most traditional one. However, the GN Hydrovac Slurry System is streamlined, compact and incredibly smart. The company adds it is a supremely durable, closed-loop system to recover solids and reduce water consumption largely.

“Based on our experience on oil gas drilling mud [and] horizontal directional drilling (HDD) mud, we have creatively developed our own procedure,” says GN.

GN designs and manufactures waste management systems for hydrovac slurry and directional drill slurry. The solution is to use liquid and solids separation equipment to treat soil, soup or slurry generated from the hydrovac or HDD projects and produce reusable construction material and discharge clean water.

System features

GN’s hydrovac system offers the complete package design for a turnkey solution, developed with many years of proven experience. Its modularised system allows for fast installation and flexible movement, while the four-phase mechanical separation provides operators with a better result.

The company’s standard hydrovac slurry separation system generally includes a scalping shaker, fine shaker, desilter and decanter centrifuge. If needed, desander cones can be added in between the shaker and desilter to compose a five-phase system.

Depending on site arrangements, GN usually has a vacuum truck drive backwards to a dumping platform and then pour through a big hopper, which collectively leads everything to the scalping shaker. The scalping shaker separates most of the stones and aggregates out, with the fluid then transferred to a shale shaker equipped with finer shaker screens to separate sand and silt out.

The GN hydrovac system removing slurry from a project site.

Like the previous step, a pump feeds it to desilter cyclones, where fluid is then pumped to a decanter centrifuge. Meanwhile, solids are dewatered by the screens underneath cyclones.

The final stage is the decanter centrifuge, which is the most important step as it considers the high solids content and normally adds in dosing polymer to eliminate tiny particles. After this, all the solids are stackable and the water is reusable.

Keep costs low

GN says its key highlights to keep clients cost as low as possible are the system’s strong screens and its tungsten carbide tiles and inserts.

The scalping coarse screen is made of stainless steel bars, which are strong enough to bear big particles and have a durable design to make sure it lasts longer. Additionally, the fine screens and dewatering screens are composite frame, offering triple lifetime compared to traditional steel frames.

GN says the screw of decanter centrifuge are covered by tungsten carbide tiles, allowing the upgraded design tiles to be more resistant and also ensure a longer life time, while the slurry ports and solids discharge ports are well protected by the tungsten carbide inserts.

This article was featured in the December 2020 edition of Trenchless Australasia. To view the magazine on your PC, Mac, tablet or mobile device, click here.

For more information visit the GN Solids Control.

If you have news you would like featured in Trenchless Australasia contact Journalist Sophie Venz at

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