DHI SOLUTIONS
Hydraulic Transient Analysis
Simulating system behaviour under various operating conditions for more
reliable and safer operations
Pressure waves can have dramatic effects
Hydraulic transients (HT), also called pressure surge
or water hammer, are planned or accidental changes of
conditions in a water distribution network, e.g. by
opening or closing a pump or valve. As a result, a
pressure wave is generated which travels through the
pipe network. Sudden changes resulting in extensive
pressure waves can have dramatic effects, ranging
from pump defects to catastrophic pipeline failures.
Transient events can also have significant water
quality and health implications.
SUMMARY
Client
 Water Utilities
 Industrial Pipeline Systems
 Hydropower
Problem
 HT analysis is essential for system design
 HT are dangerous in operation
 HT analysis is difficult
Solution
Analysis of system behaviour under HT
conditions; identification of particularly
dangerous conditions; establishing safe
operating environment
Benefits
 Safe design and operation under standard and
emergency scenarios
 Specifically tailored solutions
Pipe networks can suffer major damage from hydraulic
transients, at the worst resulting in catastrophic
pipeline failures
Establishing a safe operating environment
Surge modelling provides the most effective means of
identifying weak spots in the network and predicting
possible effects of hydraulic transients under different
standard and emergency scenarios. Moreover, the
models evaluate possible precautions and
countermeasures to establish a safe operating
environment. Model analyses are designed to predict
extremes of pressure, both maximum and minimum,
which may potentially develop within the system
during its operating lifetime and the probability of
occurrence of each extreme event, as well as its
consequences.
The transient analysis is best used in conjunction with
a hydraulic network model and includes additional
information such as the operating time for equipment
or the time for quiescent conditions to develop after
flow changes.
Hydraulic transients in the cooling water system of
nuclear power plants require thorough investigation
Design and operations
DHI carries an enormous library of various hydraulic
and surge protection devices as well as a variety of
transient sources to be included in the models.
Hydraulic transient analysis will be done using MIKE
Hydraulic Transient Analysis
Simulating system behaviour under various operating conditions for more
reliable and safer operations
URBAN FGDHT (Flow Gradient Hydraulics) Solutions
Software. DHI accurately analyses hydraulic behaviour of
your pipeline system under pressurized, transitional or
cascading flow conditions. Benefits of DHI hydraulic
transient analysis are safe design and operation of the
pipeline systems. Moreover, you will be provided with a
detailed report, recommendations and assistance in field
tests. The key information at your fingertips is specifically
tailored to your needs based on dialogue and needs
assessment.
MIKE URBAN FGDHT provides the following analysis and
methods:
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Built-in steady-state engine
Transient force computation engine
Pump and turbine modeling for fixed and variable speed units
using four quadrant curve characteristics
Rule-based control analysis
Simulation of numerous surge mitigation and protection devices
Simulation of multiple transient sources including gate and
valve movements, pump and turbine activities, and others
MIKE URBAN FGDHT can
model the following transient
sources:
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valve closure (open to close,
close to open, any position,
and to partial),
valve opening,
pump, controlled shutdown,
pump start-up,
pump trip-off,
rapid demand change,
rapid pressure change,
single source, multiple
sources,
turbine (speed, no load),
turbine (load rejection),
turbine (load acceptance),
turbine (demand change),
turbine (start-up),
turbine (shut down),
rupture disk,
pipe or a valve break
MIKE URBAN FGDHT can
model the following surge
protection devices:
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open surge tank,
spilling surge tank,
one way surge tank,
gas vessel (air chamber),
surge tank with orifice,
surge tank with bladder,
variable area surge tank,
differential surge tank,
pressure relief valve,
anti-slam valve for air
release/vacuum valve,
surge anticipation valve,
surge attenuating air.
Consequences of hydraulic transients
Our software was developed to analyse system
behaviours under various unsteady flow conditions and
to help you to understand the consequences of hydraulic
transients. These consequences include maximum and
minimum pressures in the system, occurrences of local
vacuum conditions and/or cavitations at specific
locations. These occurrences can be either within specific
devices or within a pipe. Additional behaviours that are
analysed are hydraulic vibration of a pipe, string
oscillations or rapid movement of the water masses, and
risk or occurrence of contamination at cross-connections.
Accurate modelling helps to identify and isolate
conditions that deserve particular attention.
Illustration of the MIKE URBAN FGDHT software – user
interface. DHI’s software analyses hydraulic system
behaviour under various conditions, allowing for safe and
reliable design and operation of your pipeline system
DHI provides specifically tailored solutions for proper
pipework design
Contact: Petr Ingeduld - pi@dhigroup.com
September 2011© DHI
Hydraulic Transient Analysis in Project Design: from
beginning to end
Hydraulic transient studies are especially important in
the design of water distribution systems. The severity of
transient pressures must be determined so that the
pipework can be properly designed to withstand these
additional loads. The studies are commonly included in
the Basis of Design Report to help decide upon the
required facilities and to identify differences between
alternative operating parameters. Hydraulic transient
studies are generally completed during the Preliminary
Design as their results on pressures, flows and
performance estimates are utilized in the later design
stages. Design modifications in the Final Design stage may
require repetition of transient runs to verify or modify
results. DHI will provide you with a range of tools for time
efficient model adjustments and modifications.