GEMÜ 480 and the 490 butterfly valve series

Last month, we discussed how the versatile GEMÜ 480 and the 490 butterfly valve series can be used for a wide range of applications—especially in the areas of drinking water treatment, seawater desalination, in industrial supply systems, as well as in mining and metal extraction. This month, we’ll examine the benefits these products brought to one of Singapore’s largest seawater desalination systems.


Singapore began tackling their drinking water supply problem a few years ago. The first large seawater desalination system was designed and built by Hyflux Ltd. The system operates according to reverse osmosis principle and produces more than 36 million gallons. This amount is enough to fill about fifty-five Olympic size swimming pools.

Seawater desalination runs in several process steps. The first of these is the drawing of the seawater and feeding into the system. This is followed by a multi-stage filtration, flotation and ventilation to remove suspended matter and undesirable substances dissolved in the water. The filtered water is conditioned with ferric chloride FeCl3, sulphuric acid H2SO4, hydrochloric acid HCl, caustic soda NaOH and other additives for reverse osmosis and set to a specific pH value. Without these important water treatment steps, the downstream osmosis diaphragms would become useless in no time.

GEMÜ 480 and the 490 butterfly valve series quote

After conditioning of the water, it is fed to the osmosis diaphragm modules by high-pressure pumps. The systems have a modular structure so that the diaphragms can be backwashed at regular intervals. In a system with ten modules, for example, one of them is always in backwash mode while the others produce drinking water. In the last part of the system, after the reverse osmosis, which supplies almost distilled water, the water is brought back up to drinking water quality mineral content. This is the final process step before the water is fed into the distribution pipes and sent on its way to the consumers.

GEMÜ supplied more than 760 valves in nominal sizes from DN 15-400 for this project. To offer the customers a package solution, valves have also been purchased from partner companies. The customer could therefore be offered everything from one source.

Butterfly valves with the different disc materials in 1.4408, bronze or ECTFE coated are mainly used in the seawater inlet, in the filtration/flotation and in the supply (tanks and pump stations). The nominal sizes are between DN 65 – 1400, and the operating pressure is 2.5 – 18 bar depending on the process area.


Both the GEMÜ 480 Victoria® series and the GEMÜ 490 Edessa® feature a top flange in accordance with EN ISO 5211 for mounting various operators. Hand levers (GEMÜ 487/497), gearboxes (GEMÜ 487/497), pneumatic actuators (GEMÜ 481/491) and motorized actuators (GEMÜ 488/498) in open/close and control variants are available. The pneumatic actuators can be equipped with an extensive range of accessories such as pilot valves, electrical position indicators, combination switchboxes, and positioners. Accordingly, the new valves can be integrated into any automation concept without difficulty.

For More Information

GEMÜ is a leading world-wide manufacturer of valves, automation components, and other piping products. The company has been manufacturing innovative products and customized solutions in and around the field of process media control since 1964. For more information, call 678.553.3400, email:, visit

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