Abha water utility comes out on top with automated control valves
Abha is a small modern city in the fertile mountains of southwestern SAUDI ARABIA. Its cool summers make it a popular destination for tourists, but in general the population hovers around 250,000. The city has a new reservoir on top of a hill that releases water through 6 km of piping down to its main Noaman reservoir.
The top tank is 100 meters higher than the lower tank. This makes for a great gravity feed, but gives rise to dangerous pressure differentials and also make the control valves highly susceptible to cavitation. Cavitation can be an extremely damaging force with loud noise, excessive vibration, choked flow, destruction and erosion of control valves and their components, which results in disruption of water distribution or plant shutdown.
Rafik Khan, Territory Manager Saudi Arabia said, “With the total pressure differential between the two tanks averaging 15-20 Bars, Abha needed a 100% reliable pressure reducing valve solution.” Also with multiple inlet and outlet pressure differentials a simple out of the box solution would not have worked. The engineering consultants, Khatib & Alami knew that Singer Valve is well known for creating custom valves with multiple accessory options. They recommended 6 different valves, the first two being S206-PR for the first pressure reducing station to reduce the pressure from 18 Bars to 8 Bars. These pilot operated control valves sense the downstream pressure through a connection at the valve outlet. Under flowing conditions, the pilot reacts to small changes in pressure to control the valve position by modulating the pressure above the diaphragm. The downstream pressure is then maintained virtually steady at the pilot set-point.
In addition this control valve has the Single Rolling Diaphragm (SRD) technology that provides smooth, steady and precise pressure control from maximum to virtually zero flow without the need for low-flow bypass valves. This unique SRD technology offers a huge advantage over a flat diaphragm operated valve in that it does not need to be operated between 20-80% open, so a larger diameter valve can be used to control low and high flows in the same valve.
The water then flows another few kilometers down hill to a second pressure reducing station where two additional S206-2SC-PCO with Anti-Cav Trim are installed. Singer’s Anti-Cavitation technology contains two heavy stainless steel sliding cages that maximize the full flow capacity. The first cage directs and contains the cavitation recovery, allowing it to dissipate harmlessly, while the second cage allows further control to a level as low as atmospheric pressure downstream. The cages are engineered to meet the flow / pressure differential of each application. These valves are currently open fully in order to maintain the second reservoir up to capacity for current usage, which includes supplying a nearby bottling plant.
Two additional pressure reducing valves were required to provide consistent flow over the remaining distance to customers.
Singer factory Rep Ramzi Soujah and Mr. Khan were on site for the commissioning of these valves to provide onsite technical expertise and ensure that there were no disasters. Khan said, “We were prepared to be in the pit as long as was needed to ensure the safe commissioning of the valves.” The job was concluded in four days.
Abha Water Utility Project Manager, ENG Abdullah Azeb, said, “We were insistent on a quality product and are pleased that the SRD and Anti-Cav technologies are going to assure that we have safe reliable water for our residents for years to come.”