What is a Criticality Analysis?
Criticality analyses determines the shortfall (water not delivered) when a segment is taken out of service. In calculating the criticality score for the Pipe Renewal Planner tool, the shortfall may be calculated based on distribution segments rather than pipe elements.
What is a distribution network Segment?
A segment is the smallest portion of a distribution system that can be isolated. Segments are used in the WaterGEMS V8i criticality analysis as the basic element of a system that can be isolated so that the effects of an outage can be evaluated.
If the criticality analysis has the option "Consider Valves?" disabled, then each segment consists of one and only one pipe as shown below.
If the "Consider Valves?" option is enabled, then the segments (identified by color) are created based on valves that can be closed. The segments are identified by color in the figure below. Note that the various colors assigned to elements by the program are not representative of any network attribute, but are only used to differentiate adjacent segments.
What does this have to do with Pipe Renewal Planner?
The Pipe Renewal Planner tool can use aspects, such as pipe criticality, to score pipes and help identify the most critical pipes for replacement or rehabilitation. Because scores are assigned per pipe, it is necessary for the Pipe Renewal Planner tool to assign one criticality score per pipe.
When a Criticality analysis is computed with the option "Consider Valves" enabled, there is not a one-to-one association between segments and pipes. A pipe may be made up of several segments depending on valving. The user has the ability to control how the segment shortfall is transformed into pipe shortfall.
In the figure below, there are two segments that overlap pipe 102-a short one and a long one.
The Pipe Renewal Planner tool provides the following ways to handle pipes with multiple segments:
For the example above, suppose pipe 102 is 200 ft long and 195 ft are in Segment B (criticality = 10) while the remaining 5 ft are in segment A (criticality = 60). Depending on the option selected, the corresponding scores would be:
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