Pressure management has, for many years, been considered a “quick fix”, and “quick return on investment” way of reducing losses from leaks, and “excessive” consumption in distribution lines. The methodology of reducing pressures to lower levels during low consumption periods, has evolved into a sophisticated science, with accompanying costs, and complicated equipment. The two most popular methods of achieving the lower pressure settings on pressure reducing valves, during different times of the day, use “smart” controllers. These methods are:
- Time adjusted pressure reducing valve – this consists of a standard pilot operated pressure reducing valve (POPRV), with a battery driven electronic device added to the pilot to lower the pressure setting at low demand times.
- Flow adjusted pressure reducing valve – this consists of a standard pilot operated pressure reducing valve (POPRV), with a battery driven electronic device connected to a flow meter, which changes the setting on the PRV as flow changes.
So, at high demand periods, the setting will be higher than at low demand periods. In theory, the flow method is more efficient in saving water losses than the time based method.
The above pressure management interventions provide substantial reductions in water losses through existing pipe leaks, and are implemented in many parts of the world, including South Africa.
However, a consistently frustrating issue with this method, particularly in the South African context, is that standard POPRVs are seldom maintained properly, as most operators don’t understand their functionality, and believe they will work forever. So, what happens with most of these expensive “smart” pressure reducing valves after a period of operation? In most cases, they stop working due to the operators’ poor product knowledge, no maintenance, and theft of components.
The author believes there are much simpler, and more sustainable solutions, which will provide greater efficiency, and better long-term benefits.
Ratio Reducing Pressure Reducing valves (RRPRV)
This relatively new product is ideally suited to South African conditions. Here are some of its benefits:
- Theft proof – it looks like a spool-piece and not a valve
- Relatively maintenance-free
- Very stable control with no delayed reaction time
- Able to handle very low flow rates
While a network analysis of pressures and flows by consultants is helpful, and will maximize benefits, this analysis is usually quite costly. Installing RRPRVs in high pressure areas should provide many of these benefits, without the need for the expense of an analyst.
Although they are a relatively new innovation for the South African Water Industry, RRPRVs have been around in Australia for many years, and have also been used extensively in the South African mining industry with great success.
Maric Flow Control Valve
This novel Australian product was invented some 50 years ago, and is now a world leader in tamperproof flow control. It is available in sizes from 10mm to 500mm (larger on request) and is simple, robust, self-cleaning, tamperproof and theft proof (available in PVC bodies). When installed, it is not even identified as a valve. The rubber control rings have a self-cleaning action, as they are continuously modulating, and have an average life-span of 20 years. The Maric flow control valve is used to ensure even distribution of water flow rate to multiple users, and ensures that exactly the right pressure is used at off-takes. Often, at user points where pressure is too high, an enormous amount of water is wasted due to a flow-rate which is too high for normal usage.
Air Release valves
A.R.I. have a long history of supplying air valves to a wide spectrum of Industry. Air valves serve the following functions:
- Release air when a pipeline is being filled – effective release of air greatly reduces the possibility of pipe breakages, and subsequent water wastage.
- Intake of air during pipe draining – effective intake of large volumes of air is a very critical function to prevent pipe collapse, and subsequent water wastage.
- Release of pressurised air bubbles while pipeline is operational – this function is often neglected in other valves, when it is the one function of air valves which should receive most attention. It has to be operational 24/7, and is the “Achilles tendon” of most air valves. A.R.I., however, have a patented device (rolling seal) which overcomes all inefficiencies experienced with most air valves, in which small, pressurised bubbles grow into larger air pockets, which can cause major pipe breakages. Effective release of pressurised air greatly reduces the possibility of pipe breakages, and subsequent water wastage.
Although most consultants and user engineers are aware of the benefits of controlling air in bulk pipelines, municipal networks rarely use them extensively. This is because pipe bores are smaller, and it is assumed that this means the water-hammer effects should, in turn, also be smaller. However, pipe breakages are numerous in these smaller networks, for various reasons, including sudden flow stoppages, which induce water-hammer. These effects are multiplied when air is present.
Also, in areas where water is supplied, and stopped sporadically due to water restriction measures, air valves are essential to reduce wasteful losses, and damages to consumer equipment, such as flow meters and geysers. These factors take an even greater toll on ageing pipelines, where breakages occur more regularly.
- Ultra ACV Ratio Reducing valves are available in 50mm to 300mm and up to 100bar, and will soon be manufactured in South Africa.
- Maric flow control valves are manufactured in South Africa under license.
- A.R.I. Air valves are available from large stockists, and are now also being manufactured in South Africa.