METSO Barmac B-Series VSI Crushers Specialist applications

From time to time the Barmac VSI has been applied in situations not categorised by the other four areas. Included here are a couple of sample applications.

WAG mills

The Wet Autogenous Grinding (WAG) process has been developed to solve an important problem in the oil industry.

The development was specifically related to a problem which had arisen in the oil production industry – the disposal of oil contaminated drill cuttings – these being the residual material produced when drilling for oil both on land and in marine environments.

Traditionally, these materials have either been dumped onshore or directly into the sea. However, due to environmental concerns, this practice is no longer acceptable in many parts of the world.

The material produced in these operations forms a glutenous sticky mass but, in general, has no particles larger than 25mm. In general, much of the rock is of sedimentary nature and, in the case of higher drill rates, these are often clay or shales. These materials form the most glutenous mixtures.

The Barmac VSI as part of an integrated wet-grinding system (above). This 20ft container size module was designed for use on off-shore oil drilling rigs.

Requirement

The requirement was to produce from these materials a pumpable water-based slurry which was easier to handle and could be injected back into the earth’s strata surrounding an oil well casing. This requirement was a fine grinding application, with the problem being the glutenous nature of the material.

Over a two year period the WAG process was developed to address this problem. An integral part of the process is a Barmac VSI, which was selected to address the initial production requirements related to the oil industry.

Internally, the machine is actually quite different to a standard Barmac VSI. It embodies a special weir system and other new design concepts which allow it to operate in a totally wet mode. This allows the feed and grinding zone of the machine to be ‘super saturated’ with water or desirable fluids, depending on the particular process demands.

Using this method the Barmac VSI is able to crush the cuttings and produce the required pumpable slurry.

The Barmac VSI operates as part of an integrated self-contained wet grinding system. The system embodies full particle classification, either by means of hydrocyclones or wet screening, depending on the product requirement.

For the application on drilling rigs operating in the Norwegian sector of the North Sea, a modular unit has been engineered which includes a system for recycling of oversize and the storage of the final slurry product.

While the initial process was developed to address an oil related problem, already a number of other potential applications for the system have been identified. These include the production of mining slurries for dense media separation, homogenous particle and fluid mixing, concrete slurries, sand and oil cleaning (after oil or chemical contamination) and ballasting slurries.

Dam construction

The Barmac VSI can effectively be utilised in the dam construction process.

The end stability of the dam, whether it be a concrete arch gravity dam or a rockfill dam, depends on the quality of materials used in construction. Better shape leads to better packing of the particles. This results in less voids and a structurally sound in-situ fill materials.

Material required for this type of application must be of a high quality. Not only must the materials be clean of deleterious particles, they must be of excellent shape and consist of tough clean particles.

The Barmac VSI offers both a shaping and a cleaning mechanism to the production of these types of coarse and fine aggregates. The action of the crusher breaks down soft material at a faster rate than the harder tougher particles. This results in a product that is free of softer materials that would perform poorly when subjected to the loads and conditions involved.

If the aggregate used in construction is susceptible to chemical attack, then over the working life of the dam the aggregate quality may decrease. The improved shape of the Barmac VSI product makes a sounder aggregate that is more resistant to the chemical conditions that may exist within the structure.