Critical Link Analysis Options dialog

The Critical Link Analysis Options dialog allows you to set up your options for analysis criteria, outage duration and leakage options during a critical link analysis simulation.

The dialog is displayed from the Schedule Hydraulic Run view when:

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Critical Link Analysis Options dialog

Item Description

Select Links to be included in Analysis
Selection List (drop target)

Use drag and drop or the Browse button to add a selection list of potentially critical links to be analysed.
Browse Browse Click to open a dialog from which you can choose a run.
Clear Clear Click to clear the entry in the Run box.

Analysis Criteria
Minimum Pressure and Duration

If the pressure in the network falls below minimum pressure for at least the duration period during the simulation, the test link will be considered to be a critical main and results for that link will be saved.

Maximum Pressure

and

Duration

If the pressure in the network exceeds Maximum pressure for at least the duration specified, the test link will be considered to be a critical main and results for that link will be saved.
Event Demand Efficiency

If the average ratio of actual to nominal demand during the simulation is less than the Actual/Nominal Demand specified, the test link will be considered to be a critical main and results for that link will be saved.
Failure Count Type

Set the item type at which failures are to be assessed:

If the number of items affected by the pipe failure is less than the specified number in the Ignore if count is less thanfield, the failure will be ignored.
Nodes to exclude from Analysis

Use drag and drop or the Browse button to add a selection list of nodes to be excluded in the analysis of potentially critical links.

These nodes will not be checked against the minimum pressure, maximum pressure and actual/nominal demand criteria. This may result in a test link passing analysis, which may have failed if nodes had not been excluded.
Single Pipe of Isolation Area

Select whether a single link or a group of links in an isolation area is to be closed for analysis.

Close single link for each test Each link included in the Select Links to be included in Analysis selection list will be closed separately and a simulation run. There will be one simulation run per selected link.
Close isolation area for each test
  • For each isolation area code found in the Select Links to be included in Analysis selection list, all links in the isolation area will be closed and a simulation run. There will be one simulation run per isolation area.
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    Link Outage Period
    Whole Simulation

    Link outage will be applied throughout the simulation.
    Start at Peak Network Demand Link outage will start at peak network demand determined using the demand diagram used in the run.
    Start at:

    Enter a start date and time for link outage. This time must be within the run start and end times.

    Duration of outage The outage period for the test link. This field is used when using the Start at Peak Network Demand and Start at: Date-Time options only.
    Report to end of Outage Period only Check this box to save simulation results for critical links from the start of the simulation until the end of the link outage period only.
    Leakage Options
    Include leakage (bursting) in link outage

    Check this box to include leakage representing a burst at the midpoint of the test link from the start of the outage period for the leakage duration.

    (Only enabled when using the Close single link for each test option.)

    Leakage Flow of [100mm Pipe] at [50m] Pressure [units]

    Leakage rate for a reference pipe of 100 mm diameter at 50 m pressure.

    For each test link the leakage rate is scaled as a function of test link diameter divided by reference diameter.

    Leakage is determined by actual pressure / standard pressure using standard orifice behaviour.

    Q = Cd A (2gH)0.5

    where

    Q is Discharge

    Cd is Discharge Coefficient

    A is cross-sectional area of pipe

    g is acceleration due to gravity

    H is effective Head

    The calculated leakage is applied equally at the test link end nodes and is added to any existing leakage demand. In the case where one of the test link end nodes is not a basic node, the calculated leakage is not divided between the end nodes, but is applied to the basic node only.
    Leakage Duration (mins) ~
    Allow Pipe Flow during Leakage Period

    Check this box to allow flow through the test link from the start of the outage period for the Leakage Duration.

    If this box is unchecked, the test link will be assumed to be closed.

    (Only enabled when using the Close single link for each test option.)

    Discard time varying results

    Check this box to cause time varying results to be discarded. This will save a lot of space if the summary is the only item of interest.

    If this box is checked, the run is only of use in updating criticality: when the base simulation is opened it will not attempt to open the service level report and a message will explain this.

    You update criticality by using the Update criticality option on the Network menu. See Update Criticality dialog.
    Criticality criteria options Click to view and modify the criteria to be used when determining criticality grades. See Criticality Criteria dialog.
    Service level report options Click to view and modify the settings to be used for the Service Level Summary report. See Service Level Summary dialog.
    Test cases per thread (parallel processing)

    The simulation will run for a certain number of test cases.

    The ideal is to split these exactly between the available processor cores (for example, if there are 200 test cases on an eight-core machine, the ideal setting would be 25 test cases per thread).

    Critical Link Analysis

    Criticality Criteria dialog

    Service Level Summary

    Creating and scheduling a run

    Schedule Hydraulic Run view