Pressure Management FAQs

DMA stands for "district metered area". It describes a hydraulically isolated sub-zone in a distribution network for which the water consumption is monitored by water metres.

PMA stands for "pressure managed area" and is defined as a DMA for which the supply of water is regulated with a pressure-regulated control fitting.

These terms classify the area of a PMA. Micro PMAs are smaller sub-areas of up to 500 service connections or sub-areas with a supply line of up to DN 300. Macro PMAs are large sub-areas of up to 15,000 service connections or sub-areas with a supply line of more than DN 300.

The minimum night flow is the flow measured in the supply area between 2 a.m. and 4 a.m. According to statistics, the flow rates are the lowest in this time frame, so that the water pressures in a DMA without pressure regulation will be highest. In other words, between 2 a.m. and 4 a.m. technical water losses will be highest.

The pressure management system should be installed in a hydraulically closed sector (DMA). Possibilities for isolating DMAs are included in the project area selection process and is supported by VAG experts if necessary. More information is also available in the basic requirements for pressure management and on the pressure management questionnaire.

• When pressure differences are high: a pressure difference of as little as approx. one bar between minimum and maximum pressure during the course of a day indicates a high potential for saving with the use of a VAG pressure management system.
• When flow fluctuations are high: high fluctuations in the flow of water in an area may also make it possible to save a lot with the use of a pressure management concept
• When water losses are high: water loss is frequently particularly high in old water networks due to the fact that there are many leaks. The VAG pressure management system contributes to reducing the quantity of water lost and the occurrence of new pipe fractures.
• In the case of topographical differences in altitude: pressure differences may be high when there are considerable differences in altitude in the water supply area. Pressure management can in this case counteract excess pressure and hence save water and extend the life expectancy of the network.
• The criteria for the profitability of pressure management projects are gathered with the help of an application checklist and analysed by VAG experts.

The potential for savings can be estimated on the basis of hydraulic and commercial basic parameters in connection with the possible reduction in pressure in the relevant DMA. The basic parameters are collected with the help of the VAG pressure management questionnaire.

A pressure management concept is always limited to a restricted, isolated area (DMA) that will initially need to be identified and analysed. If need be, VAG will cooperate closely to support its customers as early as in the process for selecting the economically most attractive area. Following this, a suitable pressure management concept will be drawn up for the project area. A sound, expandable system is put together with the starter kit and installed so that savings are immediately achieved. Individual upgrades can be used to optimise the performance of the system and maximise the potential for saving. Furthermore, VAG customers have at their disposal services for installed systems, training courses and additional engineering services.

The structure of a plunger valve means that it has extremely good hydraulic control properties, and it requires less maintenance.

Its construction makes it possible to control higher differences in pressure without the occurrence of cavitations. And because there are no control conduits and pilot valves, a higher degree of operational reliability is guaranteed. The considerable stroke of the piston enables the follow-up pressure to be most precisely regulated.  The use of a plunger valve avoids diaphragm-related pressure oscillation and vibrating water columns in the pipelines. The compact design, notably in the case of larger nominal diameters, also contributes to space-saving installation.

There are four different methods of regulating the pressure in a PMA with the VAG pressure management system:

• Constant control
• Time-based control
• Flow-based control
• Critical point control

The critical point is the place in the zone in question (DMA or PMA) at which the lowest supply pressure occurs during the course of the day. Vital indicators for determining the critical point are, for example, differences in altitude in the relevant network and distances from the place at which the control fitting is installed.

There are several possibilities available for the telemetry solution for transferring operating data. For example, transferring data via the mobile phone network per GPRS or GSM data services is an uncomplicated method. Alternatively, data can be communicated by means of radio signals.

Depending on the structure of the concept, the flow, the pressure directly in front of or behind the valve or the pressure at one or several critical points can automatically be recorded and saved with a SCADA system. In principle, other parameters may also be used.

The monitoring of the system can always be assumed by a SCADA system that is already present at the customer. The VAG pressure management concept is highly flexible thanks to its modular principle. VAG supports integration in technologies that are already present at a customer in other areas as well.

The pressure management systems can all be subsequently operated with other methods of regulation. For upgrading standard systems it may be necessary to integrate additional components into the system and adapt its programming.