FOCUS
top and bottom oil filled, dashpots that allow controlled closure of the valve. This is by far the most efficient valve with very low friction loss and is ideal for big pipelines. Flex check valves or rubber flapper check valves may be the most versatile check valves and can be used in both water and wastewater applications. There is one moving part which is the Buna encapsulated flapper, making it an easy to clean hardwearing valve. The valve can accommodate a position indicator allowing plant crews to determine a valve’s position quickly and easily by the visual indicator, and also a backflow actuator for preventing contaminants from entering the clean water system. “Regardless of what isolation and check valves, make sure that the valve selected meets the appropriate standards for drinking water and the appropriate standards for the valves, as this will go a long way to ensuring full life expectancy with a quality valve,” said White. “Having been in business for over 25 years, I cannot overemphasise the importance of scheduled valve maintenance to ensure longevity of use in the system. Most valves are in the ground and are easy to forget about, so setting and sticking to a schedule is key.”
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these check valve options have their own benefits and the application that they are best suited for. ‘Lever and weight’ and ‘lever and spring’ check valves are the most common check valves that are in use. These check valves can be provided with oil cushion or air cushion closure. A potential benefit of the ‘lever and weight’ or ‘lever and spring’ is that one can physically open the check valve by utilising the lever on the side of the valve. This enables operators to see if there is anything trapped underneath it if the flow slows. Silent check valves are most used on the discharge of pumps and are resilient seated to minimise noise upon closure. A downside to this valve is the added head loss across the valve. “Understanding and calculating this head loss is essential for designing efficient piping systems and ensuring the valve chosen can maintain the desired flow rate and pressure within the system,” said White. Tilted disc check valves are commonly used in high-service pumping applications where head loss is critical. Tilted disc check valves have a low head loss and can be furnished with
Images: Cla-Val
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1 Cla-Val butterfly valve 2 Cla-Val butterfly valves outside a valve station 3 Cla-Val gate valves in a valve station
IS THE LOCATION PRONE TO BACKFLOW?
The last type of common waterworks isolation valve is the check valve or non-return valve. The purpose of a check valve is to prevent reverse flow in a pipeline. There are many different styles of check valves that are available for a water system. The common choices are ‘lever and weight’, ‘lever and spring’, silent check, double disc check, wafer swing check, flex check and a tilted disc check valve. All of
Mark Gimson Director of marketing and international sales, Cla-Val
Water & Wastewater Asia | September-October 2024 41
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