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Here's how peoples energy manages direct assessment data.

Here is how Peoples Energy Corporation is collecting, interpreting and displaying data to guide compliance with the Pipeline Integrity Final rule in light of the fact that both of the company's substantial gas transmission service territories are classified as High Consequence Areas (HCAs) under the rule.

Peoples Energy's subsidiaries, Peoples Gas and North Shore Gas, operate 174 miles of transmission line. The Peoples Gas system includes 79 miles of 24-, 36-and 42-inch transmission line in Chicago. North Shore Gas operates 16-30-inch gas transmission line in part of Lake County, IL. The pipe installed predominantly since the late 1950s up to the early 1980s is coated with coal tar enamel coating. Pipe installed after mid 1980 is coated with fusion bonded epoxy coating. The girth weld coating is coal tar based hot wrap.

The Peoples Gas transmission line in Chicago is designed to Class 4 specifications. North Shore's transmission lines are designed to Class 3 specifications. Both service territories are considered High Consequence Areas (HCAs) per the Pipeline Integrity Final Rule issued in December 2003.

Testing And Analysis

External Corrosion Direct Assessment (ECDA) testing methods will predominantly be Close Interval Survey (CIS) and Direct Current Voltage Gradient (DCVG). The Pipeline Current Mapper (PCM) and PCM with A-Frame will also be used as analysis tools.

The measurement data is recorded (typed entry) into a Trimble TSCe[TM] GPS hand held data recorder. The data recorder obtains GPS coordinates from a GPS receiver carried in a back pack. The data is downloaded from the data recorder to a personal computer using a Trimble software application (GPS Pathfinder Office 2.90).

The GPS Pathfinder Office 2.90 can convert the data into many different standard file formats. The converted data (Access Database File Format Used) is imported into an Excel Spreadsheet, because Excel can read Access Format Database Files. When the Access Format Files are in Excel, the spreadsheet is programmed to compute percent IR (%IR) from the DCVG input data.

The GPS coordinates are exported to Excel in U.S. feet units. The Excel spreadsheet is used to compute linear distance in feet from an arbitrary starting point such as the north lot line of a street. Excel uses the linear distance in feet and test equipment recorded amplitude from CIS and DCVG to generate an X-Y data analysis plot. The plot is used to identify the areas which need to be classified as minor, moderate or severe. The moderate and severe classifications dictate the dig schedule for the ECDA process.

The data recorder data entry format includes a 60-character text field. The field personnel collecting data can enter geographic feature descriptions such as street name associated lot lines as the instrument test data is collected. In an urban environment, lot lines identified in the text are very helpful during the instrument data analysis.

The text data can be included on aerial or map plots produced by the GIS system. It is not good practice for field personnel to abbreviate text descriptions. The complete word or at least enough of the word should be used so it can be recognized in the future. Abbreviating the word "guard rail" as "gr" is not good practice. The "gr" abbreviation may not be remembered as "guard rail" two weeks from when data was collected. In seven years it will be totally forgotten.

The Excel spreadsheet is exported in access database format and included in the ESRI database.

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Aerial Photographs

The ESRI and Access database can then be used to plot the measurement data on aerial photographs of the pipeline. A data flow diagram is shown in this article.

Data Flow From Field To Mapping System

The GPS Pathfinder Office Desktop Application is used to build GPS data recorder data entry displays. Separate data entry displays were defined for the CIS/PCM data entry and DCVG data entry. The separate data entry displays output separate data files when the data downloaded from the data recorder is exported in an Excel readable format. The separate data files need to be combined and sorted prior to plotting data on a graph for analysis.

The GPS data entry displays were redefined to collect CIS, PCM, PCM A-Frame and DCVG field data using a single data entry display. The one data entry display exports only one data file, which is directly read into the Excel spreadsheet. The time spent in formatting data is reduced.

The field data imported into the Excel spreadsheet will be used to generate graphs. The graphs will be used to grade defects as minor, moderate or severe. The Excel spreadsheet will be exported in access database format. The GIS system will use the access database as part of its resource base to plot the data on aerial photographs. The drafting section which is responsible for maintaining the GIS database will be responsible for long term storage of the measurement data, transferred as an access database.

As new measurement data is obtained, drafting section will append new data to the existing access database retained as part of the GIS system. Data required to perform subsequent analysis, for exampie, for the next seven-year direct assessment testing cycle will be obtained from the GIS database.

The base coordinate system used by the GPS system needs to match the base coordinate system used by the GIS mapping system. The coordinate system used by Peoples Energy is shown in this article.

The data exported by the GPS Pathfinder Office Desktop Application includes X and Y Coordinates referred to as Northing and Easting, and are in United States Survey Feet (not metric). Note that the %IR and CIS measurements use their defined engineering units of percent and millivolts.

If DCVG is used as a test method, the instrument data is read in millivolts. Additional test data in millivolts is needed from test stations to compute %IR. It is good practice to have a record that the data used to compute %IR has been monitored and been consistent throughout the test period. A field report form is used for the DCVG %IR data monitoring record. The data is also entered into the GPS data recorder text field.

The data used to create the X-Y graphs and plot input for the GIS system has the following description, engineering units, and number format:

With the exception of %IR, the data is entered to the GPS data recorder in the units shown in the table. Easting, Northing, Date are automatically generated by the GPS data recorder. All the data with the exception of %IR can be passed directly to ESRI without engineering unit conversion. DCVG millivolts will be converted to %IR in the Excel spreadsheet. The test station shift within the pipe segment is used to perform the calculation.

The X-Y graph is plotted using the Line-Column graph method which is an Excel custom chart option. The DCVG or PCM data is plotted as a bar chart with magnitude scale on the left. The CIS data is plotted as a continuous connected data point single line graph with the magnitude scale on the right. Chart Options Axes selection selects the tight vertical axis to be displayed.

With the graph displayed, select the "tools" option, "chart tab" and select "interpolated," to draw the point data as a continuous line from point to point. Cells not to be plotted must be clear, not contain zero. The graph is used to identify minor, moderate and severe defects. The parameters for the classification are part of the pipeline integrity Plan.

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Parameter Name Engineering Units Number Format

CIS Millivolts XXXX
PCM Milliamps XXX
DCVG Millivolts XXXX
% IR Percent XX.X
DCVG A-Frame DBuv XX
Soil Resistance Ohm-Centimeter XX.XXX
Easting Feet Floating Point
Northing Feet Floating Point
Date Calendar XX/XX/XX
Pipe/Soil Test Station Millivolts XXXX
Text Description None 60 Characters


ACKNOWLEDGEMENT

This article is based on a presentation at the AGA 2004 Operations Conference in Phoenix, AZ. Author--Ralph Barbakoff is Coordinator, Design and Construction--Peoples Energy Corporation. He has been with the company for 29 years. His duties include serving as Coordinator Corrosion Control for City of Chicago, Direct Assessment Coordinator for transmission main in Chicago and Part of Lake County, IL (North Shore Gas Company). He is a member of NACE, serves as secretary of CAJEC (Chicago Joint Electrolysis Committee) which was founded in 1908. He serves as Second Vice Chairman of the American GaS Association Corrosion Control Committee.

Ralph Barbakoff, Coordinator, Peoples Energy Corporation, Chicago
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Title Annotation:Peoples Energy Corp.
Comment:Here's how peoples energy manages direct assessment data.(Peoples Energy Corp.)
Author:Barbakoff, Ralph
Publication:Pipeline & Gas Journal
Geographic Code:1USA
Date:Dec 1, 2004
Words:1411
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