Apr 16

The hydrocyclone body consists of three main components: Upper, middle, and lower sections. The soft orifice bushing (apex) is positioned in the tapered hole inside the orifice nut, which is threaded onto the lower section. The diameter of the apex orifice controls the spray pattern produced during operation. Tightening the orifice nut (turning clockwise) compresses the apex, thereby reducing the orifice diameter. Loosening the orifice nut (turning counterclockwise) releases compression, allowing the apex to return to its normal size. The hydrocyclone spray pattern may be adjusted during operation by varying the opening of the apex.

10”hydrocyclone components

THEORY OF OPERATION

Optimal performance of hydrocyclones requires a proper balance of feed head, feed rate (GPM),and apex opening. Improper balance of any of these variables can adversely affect performance.Two operational scenarios are presented in the following paragraphs. The first scenario describes normal operating conditions in which all variables are correctly balanced. The second scenario shows a condition referred to as “roping” which results from an improper balance of the variables.

Normal Operation

In normal operation, feed slurry is introduced tangentially into the interior of the hydrocyclone at high velocity causing a whirlpool effect to occur inside the cone. The swirling motion of the slurry drives the larger, denser particles outward against the cone wall while the smaller, lighter particles move toward the center of the cone.

The low-pressure vortex at the center of the cone pulls in the excess liquid and small particles, as well as drawing in air through the apex at the lower discharge end of the cone. The high-velocity air stream aids the upward flow of liquid and small particles toward the cone’s upper discharge, while the spiraling stream of liquid and larger particles flows downward along the cone wall toward the lower discharge. Large solids leaving the lower discharge may be further processed for removal of remaining small particles and liquid, while the upper discharge from the hydrocyclone is often routed to desilters having 4-inch hydrocyclones for removal of finer particles. Normal Operation.

Normal hydrocyclone operator

“Roping”

“Roping” is a term applied to a solid discharge stream (Figure 9000-4) flowing from the hydrocyclone. This undesirable discharge pattern results

Adnormal hydrocyclone operator

from overloading the apex opening with solids, thereby preventing air from entering the cone. Due to the apex blockage, feed material entering the cone can no longer move downward and, therefore, flows directly out the upper discharge at the top of the cone. In this abnormal operating mode, flow from the upper discharge contains large particles that would normally flow out the lower discharge at the bottom of the cone. If

 

permitted to continue for a lengthy period of time, the blockage becomes difficult to clear and the risk of internal damage to the cone increases. “Roping” discharge results in reduced solids removal capability, increased probability of wear to hydrocyclone components, and potential damage to the feed pump.

ADJUSTMENT

Hydrocyclones must be properly adjusted to operate efficiently. Tightening the orifice nut (turning clockwise) compresses the apex and thereby reduces its orifice diameter. Loosening the orifice nut (turning counterclockwise) releases the compression, allowing the apex to return to its normal size. The following paragraphs describe the spray pattern adjustments to achieve optimal performance.

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written by Decanter Centrifuge


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