Sand separator

A sand separator or a forward hydrocyclone is a device which utilizes centrifugal force to separate sand or other heavy particles out of water. The separated material drops down into a tank or reservoir where it can be removed later or in the case of in-well separators, the separated sand drops into the bottom of the well. It is not a true filter, since there is no physical barrier to separate out the particles, but it is often used upstream of a filter to first remove the bulk of the contaminant, where the filter does the final cleaning. This type of design reduces the time required to flush and clean the filter.

Additional recommended knowledge

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A hydrocyclone is a device to classify/separate or sort particles in a liquid suspension based on the specific gravity of the particles. The simple form is a cone, apex down, fed tangentially at the base. There are two exits on the axis, the larger on the base (accept) and a smaller at the apex (reject). Internally, centrifugal force is countered by the resistance of the liquid, with the effect that larger or denser particles are transported to the wall for eventual exit at the apex with a limited amount of liquid, whilst the finer, or less dense particles, remain in the liquid and exit at the base through a tube extending slightly into the body of the cyclone at the center of the base. Forward hydrocyclones remove particles with a specific gravity greater then 1, while Reverse hydrocyclones remove particles with a specific gravity greater less then 1. In a Reverse hydrocyclone the accept is at the apex and the reject at the base. There are also Parallel flow hydrocyclones where both the accept and reject are removed at the apex. Parallel flow hydrocyclones remove particles with a specific gravity less then 1.

They can be made of polyurethane, polypropylene, or other types of plastic. Metal or ceramic hydrocyclones are used for situations requiring higher wear, heat or pressure thresholds.

In a suspension of particles with the same density, a relatively sharp cut can be made. The size at which the particles separate is a function of cyclone diameter, exit dimensions, feed pressure and the relative characteristics of the particles and the liquid. Efficiency of separation is a function of the solids concentration; the higher the concentration, the lower the efficiency of separation. There is also a significant difference in suspension density between the base exit (fines) and the apex exit, where there is little liquid flow.

If the size range of the particles is limited, but there are differences in density between types of particle, the denser particles will exit preferentially at the apex. The device is therefore a means of selective concentration of, for example, minerals.

An industrial hydrocyclone will normally have a cylindrical entry section and a conical base; the angle and hence length of which also plays a role in determining operating characteristics.

Applications

• Used in micro irrigation systems to remove sand and silt particles from irrigation water. Jain Irrigation Systems is a major manufacturer of Sand Separator / Hydro cyclone Filters used in Drip Irrigation Systems.

• Grinding circuits within the mineral processing industry and micro irrigation. The coarse particles return to the mill for re-grinding while the finer products are passed on to a subsequent stage of treatment.