Todd Loudin, Flowrox USA, outlines the benefits of rubber compounding pumps and valves in helping to combat abrasion.
T
here are many different types of flotation in mining and minerals, including: column cells, which are tall round tanks that use compressed air to create air bubbles via spargers or cavitation tubes, and tank cells, which perform a slightly different flotation method and are often found on the outlet of the hydrocyclones. In both cases, level control is performed by a control valve that maintains the proper level in the column to optimise the overflow of a froth of precious metals. In column flotation, the valve controls the discharge of waste and is generally a very abrasive environment. In both situations, the control valve performs a very vital function and must be capable to survive the environment for long periods of time before maintenance. A control valve that requires frequent repairs is less than ideal. In some cases, the entire column or cell may need to be emptied for valve repair. In flotation cells, often a very simple control valve is utilised. This valve is a dart valve which is simply a plug that fits into the bottom of the flotation cell with a
58 October 2021 // global mining review
regulated opening to control the flow. This type of valve requires a box in which the valve is housed within. This metal enclosure adds significant cost to the cell overall pricing.
The correct valve for flotation control Most major flotation column manufacturers have recognised that pinch valves provide accurate control, but more importantly survive for long periods of time in abrasive environments. In flotation cell technologies, many manufacturers have eliminated the extra metal structure on the outside of the flotation cell to house dart valves and have begun to utilise pinch valves to control cell flow from cell to cell. When sizing the pinch control valve, special attention must be given to the head losses created by inlet and exit velocities and any losses through bends or elbows. Given the low driving head within a cell technology, these losses can result in improper valve sizing. A common mistake is to select a valve size that is too small for the intended flow rate. Some pinch valve companies have developed special
