Valve Isolation

The purpose of the Valve Isolation trace task is to identify valves that need to be operated (closed) to prevent flow of gas to a particular location. The results include the area affected if the valve is closed and the open valves that must be closed to isolate the area. Anticipated uses are to determine valves to be operated to prevent continued flow in the event of a gas leak, or valves to be operated to accomplish a scheduled outage in a designated location.

Configuring networks involves assigning model names to features and fields so that ArcFM autoupdaters can maintain connectivity information in the logical network. The valve isolation traces include a feature class assigned model name TBS, and a feature class assigned model name VALVE with two fields assigned model names NORMALPOSITION and OPERATINGCLASSIFICATION. The value in the normal position field indicates whether the valve is normally open or closed; the value in the operating classification field indicates whether the valve is critical. This trace also requires a feature class assigned model name Regulator with two fields assigned model names SOPIN and SOPOUT.

The Valve Isolation trace uses the SOPIn and SOPOut values to determine whether a regulator is considered a source. When determining whether a regulator is a source, the Valve Isolation trace also uses pressure. If the regulator has an incoming pressure greater than or equal to the outgoing pressure it is considered a source.

For every network feature, a weight is assigned to a field with the model name GASTRACEWEIGHT.

This trace considers only those valves that lie between the isolation point (the user-defined edge flag) and a gas source—a town border station, city gate, or a regulator (when the regulator has differing SOPIn and SOPOut values). Valves that lie downstream of the isolation point are not included in the results.

Trace operations

Find all features within the class assigned the model name TBS (town border station/city gate). These features will be considered ‘sources.'
Find all features within the class assigned the model name Regulator that have differing values in the SOPIn and SOPOut fields. These features will also be considered ‘sources.'
Find the operating pressure of the pipe on which the edge flag was placed. That pipe’s operating pressure determines which features are considered sources for that pipe. The OperatingPressure value may be stored in a field on the pipe feature class or in an Operating Pressure table that is related to the pipe feature. There MUST be a valid operating pressure value regardless of where it is stored in order to return a trace result. The Valve Isolation trace reads the pressure from this field. If the field or table is not properly configured, the trace will fail. The bulleted points below describe the configuration requirements.
- Stored in Field: The field on the pipe feature must have the OPERATINGPRESSURE field model name assigned (Field Model Names tab in the Properties Manager). This field must also contain a valid operating pressure value.
- Stored in Table: The Operating Pressure table must have the OPERATINGPRESSURE class model name assigned (Model Names tab in the Properties Manager). The table must also be directly related to the pipe feature class. The field in which the value is stored must contain a valid operating pressure value.
The trace proceeds out in all directions from the flag to each source in the network. The trace stops if it encounters a closed device before it gets to the source. It continues to the source if a closed device is not encountered.
If the Critical Valves option is selected, the trace includes only valves designated as critical.

The results include the area affected if the valve is closed and the open valves (or the open critical valves) that must be operated to isolate the area. Results are displayed (highlighted) on the map or listed as the selected set, depending on the option chosen in the Results tab. Consider the following examples:

Object Class Model Names: VALVE, TBS, REGULATOR (optional), DISTRIBUTIONMAIN (optional)

Field Name (can be any name)	Field Model Name (exact spelling)
Normal Position	NORMALPOSITION
Operating Classification (optional)	OPERATINGCLASSIFICATION
Operating Pressure	OPERATINGPRESSURE

Valve Isolation Bit Interpretations

Bit 30 - Specifies the device status and depends on the existence of the field model name NORMALPOSITION. The value of 0 means that the device is open (gas can flow through it). The value of 1 means that the device is closed (gas cannot flow through it).
Bit 29 - Specifies if a device is a valve and depends on the existence of the class model name VALVE; 1 means that it is, 0 that it is not.
Bit 28 - Specifies if a device is an essential valve and depends on the existence of the field model name OPERATINGCLASSIFICATION; the values of CIR (Critical Inspection Required) means that it is critical, and the bit is set to 1. CINR (Critical Inspection Not Required) means that it is critical, and the bit is set to 1. NC means it is not critical, and the bit is set to 0.
Bit 22-24 - Specifies isolation level; bit 22 should be set to 1 because Valve Isolation tracing is based on a single isolation level.
Bit 25 - This trace does not traverse any edges for which bit 25 is set.