Computerized Sand Re-Blending

Sand re-blending is a relatively simple process. A slurry mixture of sand, water, rocks, and organics is pumped or delivered to a sand classifying plant. An array of washers and screen decks helps to sort the larger rocks and remove or at least loosen some of the organics from the slurry.

The slurry mixture is then injected into a classifying tank. Letting gravity and fluid dynamics guide the process, the largest sand particles in the slurry fall to the bottom of the tank closest to the injection site. As the slurry moves through the tank, smaller and smaller particles fall to the bottom of the tank. The smallest particles fall to the bottom of the tank farthest from the injection point.

The tank is constantly supplied with a flow of water that keeps the tank overflowing. This constant movement of water over the edge of the tank, or weir, helps eliminate organics and deleterious material.

As the sand particles of different sizes settle to the bottom of the tank, they begin to pile up around valves in the bottom of the classifying tank. These valves are typically in sets of two or three and the valves are grouped together in stations. Each station has a sensing paddle that turns at a constant but very low speed. As this sensing paddle turns, the sand builds up around the paddle. Once the sand is piled up around the paddle, the paddle begins to stall. This send a signal to the classifying tank controller that the station area is filling up. This signal causes the valve(s) in that sensing paddle's station to open or discharge.

The sand that is discharged from each station is sent into a flume at the bottom of the tank. These flumes remix the sand and dump the sand into any of several dewatering devices. Once the sand has been separated from the water, the sand is brought to large stockpiles via conveyor belts. The sand is stored on these stockpiles to dry and then to be loaded out to customers for use in a wide variety of projects.

Some uses for re-blended sand are:

concrete mixes
masonry mixes
golf course bases and traps
fill sand

With each of these uses, a different mixture of particle sizes is required. This is called a specification. Specifications are created and expressed in a number of different ways, but all are gauged by the amount of material that either passes through or is retained by certain size sieves or screens. Specifications list how each of the sieve sizes are to be treated and how much materials must be of a certain size. Specifications are the measuring stick by which all sand production facilities are judged. Any company's profitability or their very existence can be determined by a set of samples compared with the specifications that the company is required to make.

Until recently, most sand classifying tanks were controlled by a simple electric control that gave the operator very little flexibility and even less control of the sand that was being produced. However, with the advent of the personal computer, sand classifying systems have become much more complex and much more advanced in both their features and the benefits and profitability they bring to their operators. The main benefits of a computerized control for sand classifying tanks are:

The ability to compensate for changes in the feed or slurry mix being fed into the plant. Old style controls did very little if anything to respond to changes in the feed. This lead to many stockpiles that were not made to the specifications being demanded.
The ability to monitor and report on the production of products regarding both the product's total tonnage and relative quality.
The ability to automatically make products to a predetermined specification with a mini mum of mathematical calculations by the operator. This greatly reduces the opportunity for error.

Aggregate Innovations' CSR Control makes these improvements a reality. Read on to find out more about what the CSR Control can do for your operation.