Control valves for Pressure Management

Pressure Management has become a very important element in the fight to reduce unaccounted for water losses in pipe networks. It is a “quick fix” solution, which usually brings instant results at relatively low costs. The theory of Pressure Management is that if you reduce the pressure in a network below the normal value, existing leaks will be reduced as well. The possibility of pipe breaks are reduced as well, as the whole system is operating at the lowest practical pressure. To achieve the ultimate low pressure during the complete demand cycle, Pressures would have to be adjusted all the time to match flow demands. Battery driven electronic controllers have been developed which can adjust pressures in two different ways:

1. Time modulated whereby the controller is programmed to adjust the valve’s pilot to two settings ie normal setting during high demand periods, and lower setting during low demand periods.?
2. Flow modulated whereby the valve’s pressure setting is continuously adjusted as flow demand changes. This method is more expensive and complicated as a flow meter is required with the PRV installation. Savings using this method are optimized.

How does all this affect the control valve selection process?

Every Pressure Reducing valve has a particular pressure drop ratio it is able to handle without cavitation occurring. For most standard control valves this ratio is 3:1 ie if the incoming pressure is 9bar the valve can comfortably handle an outlet pressure of 3bar. In a lot of cases it would be possible to reduce the pressure to say 2.5bar (which would make a great improvement to savings), but it would mean that the control valve is operating in its cavitation zone and seriously reduce the life of the valve. The other problem with cavitation is that air is released with a lot of inherent instability which could result in pipe breaks and which would have the opposite affect of what one is trying to achieve ie?saving water.?Pressure reduction ratios need to be carefully checked to ensure that critical ratios are not exceeded. Most standard control valves with max 3:1 capability would have to install two valves in series in the above pressure scenario. Two valves in series increases the cost and complexity of the installation as well as increasing potential instability, which can also lead to pipe breaks.?The Ultra Alpine ACV Control valve can handle a 4:1 ratio, which would allow the downstream pressure to be set down to 2.25bar.?

The other problem area to investigate is the valve’s ability to handle low flow during night-time demand. All standard control valves have a minimum flow rate at which it is able to control in a stable fashion. If flows go below this value, the valve becomes unstable and is likely to cause pipe breaks. Standard control valves would have to overcome this problem by installing a smaller valve in parallel and which would automatically handle the low flow during nighttime demands. Again this adds complexity, cost and possible instability. Some manufacturers have a V-ported valve which can handle lower flows.

Ultra-Control Valves?supply 3 different types of Control valves:

• Ultra-Alpine ACV?Diaphragm Operated Control valve. This valve is like the standard competition’s range although it has significant benefits such as higher Pressure drop capability and longer life due to robustness and internals which are easier to service than other valves. This valve is based on the Cla-Val design, and which has a worldwide reputation of excellent design.
• Ultra-Elite Axial Flow Valve?This valve is a unique design with an axial flow path which allows it to have a 12:1 pressure drop capability and can also cope with much lower flow rates without instability.?
• Ultra ACV Ratio Reducing valve

This valve reduces pressure in a Ratio and does not use any pilots and as such is the simplest form of Pressure Reducing valve. In Water Loss Control by Pressure Management, the Ratio Reducing valve has the following uses:

1.?????As a simple Pressure Reducing valve. By installing this valve in any system where the pressure is higher than it needs to be,?the simple reduction of the pressure envelope will result in water savings

2.?????Where the reduction ratio is higher than the Ultra ACV Pilot operated valve can handle, placing a Ratio Reducing valve upstream of the Pilot operated valves will solve any Cavitation problem. Whereas 2 x Pilot operated valves in series can cause instability problems, the Ratio Reducing valve just acts like a passive device which immediately follows what the Pilot operated valve is doing without any instability.

As a major Manufacturer and supplier of Control valves in South Africa, Ultra pride themselves on their application knowledge and field service of control valves.

Ultra-Alpine have a complete system of electronic equipment with Cloud-based monitoring and control. It also has a Electric Generator which is fitted across the inlet and outlet ports of the control valve and which generates the required electric current to drive the equipment without the need for battery driven equipment.

Together with associate companies, the complete service of Water Loss Management can be offered ie

• Leak Detection
• Data Logging
• Compiling a report of requirements for a network to optimize pressure settings and minimize losses.
• All related field service and commissioning.

In most parts of the South African Water Industry, maintenance is not performed and Ultravalves offer a service to ensure that all its Pressure Reducing valves are regularly checked and perform well. Just this simple strategy will already have a huge impact on water saving, without any additional??electronic equipment.

Peter Telle, CEO.