Reducing water losses by intelligent VAG pressure management

Apr 30, 2008

Leaks in water pipes and leaking valves in urban water distribution systems and pipeline networks, mainly in developing and threshold countries, are the reasons for water losses of up to 50% in relation to the water quantity being produced in the water works.

General Problem
To overcome this problem, more than often investments which are made in the water sector, are first of all made under the aspect of increasing the production, and not to generate programs to reduce the water losses.
To change this way of thinking, the most economic - and ecological - solution therefore is to reduce the water losses in the distribution systems and not permanently increase the water production. Whilst production capacities are being increased, the structure of the pipeline system, originally designed for much smaller output volumes, remains the same. In particular, the valves which have to regulate the flows and pressures to maintain a constant supply of potable water cannot do their job in an adequate way. If those valves cannot be controlled exactly, this will lead to high pressure differences in the piping system, to pipe bursts, and, ultimately, to a complete collapse of the entire distribution system.
This is the task for regulating and control valves, which will control flows and pressures, or just open and close water distribution pipelines.
How to Reduce Water Loss and Pipe Bursts?
With an innovative concept VAG-Armaturen GmbH offers 3 different solutions to make an important contribution to the reduction of water loss. The systematic reduction of pressure in the main water supply system enables the utilities to reduce their water loss to sustainable economic levels.
Method
A control device (Plunger Valve) and a pressure sensor together with a flow meter are installed at the supply area's feed point. A programmable logic controller (PLC) records, processes and archives the measured sensor data that are needed to control the Plunger Valve. Depending on the supply system's topography and consumption, the valve is moved into the position that optimally reduces the supply pressure. Reducing the supply pressure reduces the amount of lost water. Positive side effect: Reducing the supply pressure reduces the risk of new leaks occurring in the supply system.
24 hours x 365 days monitoring of the supply system
The feeding volume and supply pressure are constantly monitored and available for the customers review and further analysis. Secure cellular technology is used to transfer the data to a PC that is connected to the internet. A software programme enables the utility to follow the valve's operation online, making laborious journeys to remote supply points a thing of the past. Failures are sent directly to the responsible service team of the utilities in the form of an SMS alert. Their service personnel is only notified when they're needed, saving them time and of course additionally expense. A local control cabinet enables the utilities to monitor the pressure and operate the valves by hand. All of the important operating information can be viewed on a text display. Control parameters can be viewed and changed on site without any assistance from VAG.
System
The system solution from VAG consists of several components (as you can see in picture 1). The picture displays a by-pass solution that enables a water utility to mechanically override the control device at any time. At the heart of the system is a VAG Plunger Valve. Based on the type of local power supply in the utilities network system, the control valve is powered by a DC, AC, or three-phase actuator. A flow meter continuously records the actual volume of water that is supplied to the distribution area. The pressure sensor behind the by-pass is used as actual value for the pressure reduction function of the PLC. Status information about the volume taken, the measured pressure and the actuator converge here.
Inexpensive Installation
There is a certain amount of civil works required for installation, however compared to the large savings potential, the initial investment is very small. VAG will assist utilities to determine the right place for the installation and create a list of the required activities. Each customer of VAG will receive a proven, total system consisting of a Plunger Valve, pressure sensor, flow meter, a programmed controller and, optionally, a cellular modem to transfer data to the customers central control station. In addition to the usual quality tests performed at VAG facilities, the system is put into operation at site by one of the qualified VAG engineers. A training course for the engineers of the utilities could also be part of the VAG package.
The VAG RIKO® Plunger Valve can reduce the pressure in the customers’ network by using the following modes:
  1. Time Based Modulation
  2. Flow or Demand Based Modulation
  3. Remote Node Based Modulation
 Each mode of operation offers different control characteristics and benefits which may be selected to meet the budget and the engineering requirements as described in the following text.
1. Time Based Modulation (picture 2)
This method is achieved by using a controller with an internal timer to change the set point of the fixed outlet control. Control is affected in time-bands in accordance with the demand profiles.
Time based modulation is very effective for areas with stable demand profiles and head loss and is usually used where cost is an issue, but a more proactive pressure management is desired, for example where night time pressure is to be reduced for a number of hours to reduce the effects of leakage. The step before the Time Based Modulation is the so-called Fixed Outlet Modulation which is the most basic control and which is achieved by simply modulating the valve to provide a steady outlet pressure (set point) as system flow demands change, and which VAG Plunger Valves can of course handle as well.
2. Flow or Demand Based Modulation (picture 3)
More water can be saved and more pipe bursts can be avoided when the pressure is following the demand cycle during the whole day, week, month and year.
A flow meter in the main supply pipeline recognizes the current demand for water in the network. This value is sent to a computer, where an evaluated curve specifically for this network is stored. The curve shows the minimum pressure which is necessary to maintain the related flow rate. This method has in the past proven to be the best type of control for areas with changing conditions, head loss, fire flow requirements and the need for proactive control. As demand is reduced primarily at night, pressures are reduced then and when demands peak, higher pressures can be applied to the district. The effect is an efficient control of pressure and the water losses. Additionally as pressures are smoothed out at the weaker extremities of the system the number of new pipe breaks is reduced.
3. Remote Node Based Modulation (picture 4)
With the Remote Node Based Modulation the pressure will be measured directly in the network at a critical point. The signal is sent via a wireless connection to the control valve.
This type of control is probably the most proactive and is affected by connecting a remote pressure sensor to the valve controller, by means of radio or GSM. The remote sensor is usually placed at a critical point in the district and the controller set to change the pressure at the valve to always maintain the desired pressure in the network system. As with the flow based modulation discussed above this mode of operation also smooth's the system pressure at the weaker extremities and has the added effect of reducing the number of new pipe breaks.
The Heart of VAG Pressure Management
The VAG RIKO® Plunger Valve precisely regulates the pressure in a piping system and guarantees the constant supply of water at any time, at any condition, in perfect coordination of both flow rate and network pressure.
Previously, only the term of needle valve was used for valves having a controlling function. Today, the term Plunger Valve is very common due to the design features shown in picture 5:
  • The cross-section of the flow is annular in each position of the valve
  • The axially movable closing device is shaped like a piston or a plunger
VAG-Armaturen has redesigned the existing Plunger Valve which was already established in the market for many decades. Today the new VAG RIKO® Plunger Valve is available in nominal widths from DN 150 up to DN 1600 and in the pressures ranging from PN 10 up to PN 40. The compact and single-piece body is made of high quality ductile cast iron (GGG-40) with an inner body which is connected to the outer body by cast ribs. On the upstream side, the inner body has a spherical shape and the shape of the annular space results in a continuous narrowing towards the seat on the downstream side. Depending on the hydraulic conditions, there are different outlet parts available (picture 6-8). The cross-section is reduced in its flow, which is symmetrical to the axis, until the fully closed position of the piston is reached and the valve is absolutely drop-tight. The piston or plunger is normally made of stainless steel and is operated by an internal piston-drive made of ductile cast iron or stainless steel. An essential advantage of the new VAG RIKO® Plunger Valve is its piston guiding which is made of welded bronze. The piston-drive is connected by a stainless steel shaft to a gear box assembled to a connecting flange on the outside of the body. New sealing systems for pistons, shaft bearings and seats guaranty a good corrosion protection and high performance combined with a long life time.
Range of application
Plunger Valves are designed to fulfil special control functions in the water supply systems. Unlike Butterfly or Gate Valves which assume only shut-off functions in pipeline systems, Plunger Valves meet the special requirements of regulating operations. VAG Plunger Valves can be used for potable water up to 50°C (122°F). Due to the linear regulating characteristic the VAG RIKO® Plunger Valve guarantees best cavitation behaviour with lowest friction-loss at the same time.
The project Santo Amaro in the Metropolitan area of São Paulo, Brasilia
The water consumption in the Metropolitan area of Sao Paulo is continuously increasing. Today, for the local water suppliers -namely the state owned company SABESP - Companhia de Saneamento Básico do Estado de São Paulo - it is a challenge to meet the demand of the 17 Million people of Sao Paulo and ensure a constant supply of potable water in sufficient quantities. Despite the quality service provided by SABESP it is possible to experience periods of rotational supply caused by lack of resource during a dry period. One reason for lack of water supply is the high volume of - physical- water losses which occur during operation by leakage at critical points like mains and fittings, if the pressure can be managed effectively, then water loss will be reduced.
The VAG task was to combat head loss and to apply pressure to the pipeline system when required and reduce pressure off the pipeline system when legitimate demand is at it lowest. This was achieved by installation of an intelligent pressure reducing valve - the VAG RIKO® Plunger Valve - operating on a remote node modulation basis.
The solution of VAG
Supported by the German Government and in co-operation with the DEG - Germany Society of Development- and SABESP, VAG-Armaturen GmbH started a PPP-Project for Sustainable Water and Natural Resources Management in Sao Paulo in March 2004, and in August 2005. VAG and SABESP installed in a pilot site in the District of Santo Amaro with a population of about 30.000 people and 80 kilometres of distribution pipes consisting of a highly sophisticated  water loss reduction system consisting of pressure regulating valves, control panels, telemetry installations, and the supporting software. This pilot site has demonstrated that modulated pressure management significantly reduces both the volume of water loss and the frequency of new pipe breaks occurring. For the Santo Amaro district this means a reduction of up to 50% of new pipe breaks and 30% volume, which is sufficient to supply an additional 8,000 people with potable water this is of particular significance in a fast growing Metropolis like Sao Paulo, and also important for other municipalities all over the world.
In the meantime the VAG Pressure Management System is approved in several applications worldwide. The savings caused by reducing water loss and by the reduction of new pipe breaks are very high and the investments will be amortised within a short time period. You will find further details of VAG Pressure Management on the animations below www.vag-armaturen.com.
Literature

1. Flyer VAG Pressure Management Technologies
2. Flyer VAG Pressure Management Solutions
3. Flyer VAG RIKO® Plunger Valves
4. R. Heiler, Valves for the Water Industry - 1994

Contact

Peter Oppinger (Head of Marketing, VAG Armaturen GmbH)

68305 Mannheim, Germany

Phone:

+49 (621) 749 2106

Fax:

+49 (621) 74929 2106

E-Mail:

P.Oppinger@vag-armaturen.com

Internet:

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