Yarra Valley Water (YVW) is the largest of three water corporations in Melbourne, Australia, providing water supply and sewerage services to over 1.7 million people. The district covers approximately 1,500 square miles (4,000 km2) and maintains over 5,500 miles (9,000 km) of water mains and nearly 5,500 miles (9,000 km) of sewer mains.
The utility's Wandin North site had three Pressure Reducing Valves (PRVs) of differing sizes. The 2" (50 mm) valve was used during periods of low demand in the zone, while the 4" (100 mm) valve supplied water during periods of high demand. The 6" (150 mm) valve supplied water during extremely high demand periods, such as fire fighting. In early 2012, YVW's Field Service technicians (Lend Lease) observed severe erosion within the 2" valve during routine maintenance at this site.
Noise from the valves could clearly be heard from the in-ground concrete valve chamber with the concrete lid on. The three valves at the site were not fitted with anti-cavitation trim at the time of installation, as the design did not require it. Typically an anti-cavitation trim is needed when the inlet pressure is three times higher than the required outlet pressure or when the Sigma is below 0.8. Inspection showed the site's upstream (inlet) pressure transmitters to be 68 m and downstream (outlet) to be 6.6 m. This meant the downstream pressure (desired set point), which feeds into residential homes, was fluctuating due to the cavitating valves that were struggling to provide a stable downstream pressure. It was clear that an anti-cavitation trim was needed and the damaged 2" valve would have to be replaced.
However, replacing the 2" valve with an added Anti-Cav Trim would still leave the other two valves vulnerable to cavitation. Smaller diameter valves can maintain control at lower flow rates, butt hey offer limited capacity for high flow rates, hence the additional valves in the system. As luck would have it, Singer Valve added new sizes to its Single Rolling Diaphragm (SRD), starting at 6". This technology offers a huge advantage over a flat-diaphragm-operated valve in that it does not need to be operated between 20% and 80% open, so a larger diameter valve can be used to control low and high flows in the same valve.
Most distribution systems have a combination of extremely low-flow and high-pressure periods. Traditional automatic control valves often experience seat chatter under these conditions. As a result, a smaller bypass valve is needed to control the lower flows. With the Singer SRD technology, the molded diaphragm provides a constant surface area no matter the valve position and avoids injecting small pressure pulses into the piping. By doing this, the valve eliminates seat chatter at low flows, helping to prevent water loss and leakage while providing smooth, precisely controlled flow.
"It goes against the 'rule of thumb' to remove a smaller diameter valve from a system and expect a larger diameter valve to control pressure during low and high flows," said Metaval Sales Engineer Steven Hill. "But the SRD worked like a charm."
By replacing the 2" valve with a 6" SRD fitted with Anti-Cav Trim, it removed the need to protect the other two valves with Anti-Cav Trim as the one valve can now do it all.
"Another advantage that is significant over time is that we now have fewer assets, requiring less maintenance," said Fiore DiPietro, a specialist technician at Yarra Valley Water. With an organization that requires 650 people to maintain operations, finding ways to reduce maintenance time and costs can make a big difference.
Singer Valve is exhibiting at AWWA's ACE14 expo in Booth 2063.
