Water utilities and developers

Water distribution networks

Surge analysis / transient analysis

Technical description

Halcrow has extensive experience and comprehensive in-house capability in hydraulic surge analysis and modelling

Surge transients (water hammer) can destroy pipe systems, cause contamination of clean water, and cause leakage or bursts on both major and minor hydraulic systems.

The potential for severe surge transients should be assessed for all hydraulic systems so that catastrophic system failures and unnecessary leakage and contamination can be avoided.

Halcrow has a team of hydraulic specialists with experience of surge transient analysis and modelling.

Emphasis is given to understanding the nature and risk of worst case surge transients on a given system. Our analysis enables worst case surge transient scenarios to be identified prior to model development.

Once a potential risk is identified, sophisticated software is used to develop a model to determine the severity of the risk, and to examine the effectiveness of potential solutions.

Projects

Surge transient analyses have been carried out by Halcrow for a number of major companies in the UK and overseas including :

Anglian Water ( Weelsby Distribution System, Thornton and Goxhill Boreholes, Mousehold to Strumpshaw Trunk main System, Ecton Booster Station )

Defence Estates ( RAF Lakenheath Air Base - Ring Main System )

Hyflux (The Palm Jumeirah)

Mid Kent Water ( Kings Hill Booster Station, Kingston Pumping Station , Bewl Reservoir Pumps , Ford Pump Station)

Southern Water ( Micklemersh Pump Station )

Modelling

Halcrow is able to choose from a number of different software packages for carrying out transient analysis, depending on whether the client has any particular preference. In previous work, we have used commercial packages, such as Surge5 and the Halcrow in-house software package, known as Coup.

These packages are used mainly on water supply and wastewater systems. For other fluids, we could arrange to use the well-known Flowmaster software suite.

The above software provides a platform for constructing a model of the closed conduit system and computing the flows and pressure transients that can occur.

This is achieved by solving the basic equations of fluid mechanics for the transient flow of an incompressible fluid in a pipe network. The hydraulic components that are usually responsible for creating surge transients are valves and pumps, usually as a result of operational changes that cause the fluid to depart from its steady state condition.

The different software all provide a full range of valve types and a number of standard pump settings based on specific speed. Pumps are modelled using input pump curves extended to four quadrants where necessary by the use of the Suter model. For this approach, normalized pump data is stored in files for various pumps. A number of components are also included in the software for the alleviation of surge transients, such as surge vessels and pressure relief valves.

Transient Analysis Strategy

Most analyses involve three distinct phases. An initial evaluation phase is crucial to identify the likely worst case transient events and the need, extent and nature of modelling required. For some systems, it is possible to negate the need for further analysis at this stage.

A modelling and design phase follows, in which the most realistic modelling of the worst case scenarios is undertaken, solutions formulated, and verified by modelling.

Finally, the reporting phase produces reports and charts that demonstrate the nature of the transient problem, the details of solutions, and background data that may be required by the client or contractor.

Data Requirements

The first two phases of a study require extensive project information. Often this can be gathered without a site visit, but site visits and meetings can provide further important information.

Integrated Teams

At Halcrow, we understand the need to provide integrated teams with the right mix of skills to meet the needs of modern projects. Our experienced team of hydraulic transient analysis engineers can draw on the expertise of in-house specialists in p ressurised water systems.

Halcrow also has a team of highly capable m echanical and electrical engineers allowing us to provide a service in which we can tailor our analysis to specific problems to find unique solutions.