Applications and Solutions -

Transmission and Distribution

Transmission and Distribution

A Water Distribution Network (WDN) is an essential infrastructure, meant to supply indigenous, fresh water within boundaries of a city or designated area. A distribution system that supplies drinking water from the points of supply, to the points of consumption, consists of pipelines, valves, tanks, pumps etc. and supplies water to consumers, under certain hydraulic conditions that are often difficult to control mainly due to constant growth of population. The purpose of the WDN is to provide water to the consumers, not only of adequate quantity and optimal pressure but also of the quality in compliance with local regulations. However, smooth running of large-scale water supply networks is still a major engineering challenge due to many factors affecting such as:

  • The topographic complexity of the network
  • Complexity of the network connections
  • Different functional regulatory systems
  • Temporal and spatial variations in water demand
  • The friction between water and the internal wall of the pipelines
  • The existence of Non-Revenue Water in high percentages

Valves generally used in a water distribution system are isolation valves (or stop or shutoff valves) and control valves. SIGMAFLOW make isolation valves (typically either gate valves or butterfly valves) are used to isolate sections for maintenance and repair and are located so that the areas isolated will cause a minimum of inconvenience to other service areas.

Maintenance of the valves is one of the major activities carried out by a utility. Many utilities have a regular valve-turning program in which a percentage of the valves are opened and closed on a regular basis. It is desirable to turn each valve in the system at least once per year. The implementation of such a program ensures that water can be shut off or diverted when needed, especially during an emergency, and that valves have not been inadvertently closed.

Factors affecting pressure in Water distribution system :

  • Inlet Pressure: Higher inlet pressure is always considered to be conducive to improve the outlet pressure, reducing the pressure drop along the pipeline.
  • Flow Rate: As the flow rate increases, pressure also increases.
  • Transport Distance: The outlet pressure of the pipeline gradually decreases as the transport distance increases.
  • Roughness of Pipe: Under certain inlet pressure conditions, the pressure drop in pipe increases with the rise in pipe wall roughness.

Benefits of controlling pressure in Water distribution networks :

  • Reduces surges and excess pressure
  • Lowers pipe failure rate
  • Extends pipe service lives
  • Improves water distribution management
  • Lowers water loss through leaking pipes
  • Saves water and energy cost

Control valves used to control the flow or pressure in a distribution system. They are normally sized based on the desired maximum and minimum flow rates, the upstream and downstream pressure differentials, and the flow velocities. SIGMAFLOW offers typical types of control valves include pressure- reducing, pressure-sustaining, and pressure-relief valves; flow-control valves; throttling valves; float valves.

Most valves are either ductile cast iron or grey cast iron, although those found in premise plumbing to allow for easy shut-off in the event of repairs are usually brass. They exist throughout the distribution system and are more widely spaced in the transmission mains compared to the smaller-diameter pipes.

Other valves include in a water pipeline are air release valves, which are typically located at very high point on the main or a gradient change point. SIGMAFLOW offers an array of air valves for distribution lines. For details, see the product section.

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