A distribution network segment is defined as the smallest portion of a distribution system that can be isolated. Segments are used in the HAMMER CONNECT criticality analysis as the basic element of a system that can be isolated so that the effects of an outage can be evaluated.

HAMMER CONNECT allows a user to set up two types of segments:

1. Using valves - A segment is created when valves are closed to isolate a portion of a distribution system. If the user has entered isolating valves and these valves are assigned to pipes, then HAMMER CONNECT automatically identifies segments. These segments can consist of a portion of a single pipe or several pipes and their interconnecting node elements. The user selects this type of segment by checking the "Consider valves?" box in the Options tab of the Criticality Studies manager.
2. Pipe-by-pipe - In some cases a user wants to conduct a criticality analysis but does not have information on the location of isolating valves. In this case, HAMMER CONNECT will create segments such that there is one pipe link in each segment. The nodes at the end of the pipe links are not part of the segment when this method is used. The user selects this type of segment by unchecking the "Consider valves?" box in the Options tab of the Criticality Studies manager. This type of analysis is less accurate than that using valves but still can provide insights in terms of reliability.
3. Valve-by-valve – in some cases a user wants to analyze the effect of having an inoperable valve on the size of a segment and the resulting shortfalls if one of these larger segments. This is useful for prioritizing valves which need exercising and maintenance. . In this analysis each selected valve is treated as inoperable in the open position and the resulting new segment is created and its properties determined. The segment is bounded by the elements that need to be closed in order to isolate the valve. The new segments created based on the inoperable valve are labeled using the label of the inoperable valve.

The first figure below shows a simple pipe network with valves:

If the "Consider valves?" Option is selected, 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.

If on the other hand, "Consider valves?" is unchecked, then each segment consists of one and only one pipe as shown below.

If you are analyzing critical valves, then the segments are determined differently.

The option where valving is considered is a much more accurate reflection of the portion of the system that is out of service during a shutdown. Using the pipe-by-pipe segments can be misleading in come cases. For example if pipe P-8 is removed from the system, then by considering valving, the user can see that all downstream customers are out of service. However, in the pipe-by-pipe case, J-1 and J-6 are still in service and it looks as if downstream customers can be served.

Of course, to consider valves in the system, the isolating valves must be part of the pipe network. Adding isolating valves is explained in topic "Valves - Isolating."

Depending on the approach used by the modeler, elements such as PRVs and General Purpose Valves may also be used to isolate segments. For each of these types of elements, the user can indicate whether they should be used to isolate the system. For each type of element, the user has three options:

• Always use (default) - valve is treated as an isolating valve for segmentation
• Use when closed - status of closed if assigned in initial conditions for that scenario
• Do not use - does not use valve as boundary to segment

There are several buttons on top of the middle pane in the segmentation manager that are used to control the display of segments in the drawing and use of segmentation results.

The first button enables the user to Create a Selection Set including all of the elements from a specific segment. When the user picks this button, the user is given an opportunity to name the selection set. Hitting OK creates the selection set. The set includes pipes that are only partly in that segment. The user can also add the elements in the segment to a selection set or remove them from a selection set.

The second button Zooms to the selected segment and highlights the elements in that segment. If a pipe is only partly in that segment, the entire pipe is highlighted.

The Find in Drawing button is used to pick an element from the drawing and determine which segment it lies in. When the user picks Find, he is given a "Select from Drawing" prompt and must pick an element. The segment that the user picks is then highlighted in the middle pane list of segments and the details are given in the right pane. If a segment boundary valve is picked, then the segments on both sides of the valve are highlighted.

The Highlight Segments button color codes the drawing such that each segment has a different color. If All Segments is selected in the middle pane, then all segments are color coded and if one is selected, only that segment is color coded. Repeating this selection toggles off this color coding. This color coding is not a property of the element and as such is not handled by the Element Symbology tool and if an element is moved after this color coding, the color coding is not moved. It is usually advisable to minimize the segmentation dialog when viewing color coding.

For criticality valve studies, you must select a single segment for highlighting. If you select “All Segments” then only the first segment in the list is highlighted. This is because segments are generally overlapped when analyzing critical valves where critical pipes normally do not have overlapping segments.

The next button is the standard Refresh button which refreshes the drawing if needed.

The next button is the Report button which generates a report for printing.