The document describes the design and implementation of a GIS-based support system for gas distribution network design. Key points include: - The system was developed to improve the design process by integrating spatial and non-spatial data, standardizing procedures, and facilitating analysis and visualization. - A geodatabase model was created and implemented in ArcGIS to manage network data during all stages of the design. Twenty-seven specialized processes were developed for designing and extending the distribution network. - Testing showed the system provides a framework for managing data and executing the full design process in a standardized way from inputting maps and consumption data to hydraulic modeling and network layout. This improves over disconnected existing methods.

1. 26
The main parameters in evaluating a gas
distribution network design include:
• Reliability of resulted network in providing proper gas pressure
• Cost of implementing the network
• Management capability and flexibility of the network in the
occurrence of crises/events
On the other hand, the following problems regarding the
design of the distribution networks should be considered:
• Most of the maps and procedures are done in a CAD-Based
system. Although they are powerful in visualization, they uncon-
vincing in analysis
• Incoherence and separation of stages and processes of the
design done by different people
• Lack of a proper data management
DATA AND MAPS GENERATED DURING NET-
WORK DESIGN
A large portion of the information used by gas distribution com-
panies is gathered and created during the distribution network
design. The data is created and stored in the form of DWG
files,Tables and Reports. These include the map data of blocks of
the city, node-map, designed network, land ownership, feeding
network, etc., and the tabular data consists of the results of the
market analysis, results of the network hydraulic calculations,
list of the material used in the network, and the customers
information etc. (A'inechi, 1993).
UNITS INVOLVED IN THE DESIGN OF THE
GAS DISTRIBUTION NETWORK
Different processes and stages of the network design are done by
many engineering units. This includes market analysis unit, the
network control unit, the design unit, cathodic protection unit,
surveying unit, implementation unit, customer service unit, and
emergency unit. Also there are different duties and responsibili-
ties, a need for diverse map and other datasets needs.
GENERAL GOALS OF USING GIS IN THE
NETWORK DISTRIBUTION DESIGN
The customers of the gas are distributed in space and the design
should follow the spatial pattern of these customers. In other
words, the design of the distribution network is a spatial design
and spatial decision problem. Therefore, GIS as the most power-
ful and commonly used spatial analysis tool, can be used to
improve different aspects of the distribution network design.
As mentioned by Boulos (2004), introducing and using of GIS
in different stages of the network design will bring about many
benefits. This includes the reducing of data redundancy and
improving of data sharing among different units and processes,
OIL & GAS
G I S D E V E L O P M E N T - M I D D L E E A S T J A N UA R Y - F E B R UA R Y 2 0 07
SAADI MESGARI I REZA NOURJOU I HOSSEIN AGHAMOHAMMADI
SUPPORT SYSTEM
FOR GAS DISTRIBUTION
NETWORK
The paper details on the design and implementation of gas distirbution network.

2. better data management, providing of
data query and analysis tools, providing
of visualization tools for representation
of data and analysis results, improve-
ment of system and optimization of
processes, providing of the development
tools for improvements regarding data
editing and data quality control.
DESIGN AND IMPLEMENTA-
TION OF A GEODATABASE
FOR THE DESIGN AND
EXTENSION OF THE GAS
DISTRIBUTION NETWORK
The Geodatabase model is an object ori-
ented data model. In this model, intelli-
gent objects are created that simulate the
natural attributes and behaviors of the
real-world features. It also models the
relationships between the real-world fea-
tures (Zeiler, 1999).
Among the benefits of using a Geodata-
base model, the more important ones are:
the ease of creation, editing and analysis
of geometric networks, the ease of edit-
ing data with topological relations, the
controlled data entering with easily
defined regulations and rules, protection
of the consistency of the database, and
finally the ease of developing application
programs for accessing data in Geodata-
base using SQL sentences and user-
friendly interfaces.
Some of the rules that can be imple-
mented in a Geodatabase are:
• Geometric network rules
• Spatial rela-
tionship rules
• General rela-
tionship rules
• Attribute rules
Geodatabase
comprises the
central part of the
GIS. All processes
related to spatial
and non-spatial
data manage-
ment, quality con-
trol and data inte-
gration are done
by Geodatabase (Marv 2002). Using the
Geodatabase capabilities, Geometric Net-
work, and UML, the conceptual model of
the spatial database required for the gas
distribution network was created.
ArcGIS software was selected as the
basic software environment for the
implementation of the system. The
designed conceptual model was imple-
mented using the available tools of Arc-
Catalog. The result of this procedure was
the creation of a Geodatabase with a set
of empty layers along with empty data
fields and defined relations. Figure 1
shows the layers of the implemented
Geodatabase. Some of required processes
are implemented using the existing tools
and functions available in ArcGIS. For
many other required processes, suitable
tools and functions are developed and
added to the GIS using the programming
environments of VBA and ArcObjects.
DESIGN AND EXTENSION OF
GAS DISTRIBUTION NETWORK
The designed and developed GIS provides
a proper framework for the management
of the data and execution of all design
processes. For the design of a city’s gas
distribution network, we only need to
enter and fill in the defined data layers
and tables and start the sequence of the
processes as defined in the system.
The main difference between such an
extended system and a usual multi-pur-
pose GIS is that, all tables and layers of
the database are empty and during the
design procedure, the generated data are
entered to the proper layers and tables,
according to the specified standards and
rules. In addition, some parameters of the
quality and correctness of the data are
controlled by the system. The implemen-
tation of the required and developed
functions are grouped in a new module
called GGIS, which is added to the user
interface of ArcMap and can be used easi-
ly by the units involved in the design pro-
cedure. This module and its developed
functions are represented in Figure 1. The
developed system is tested and evaluated
using the dataset of a region of Tehran
city called Khoshnam.
In the following, the twenty seven
processes developed for the design and
extension of the distribution network are
described. The combination and sequence
of processes is summarized in Figure 2.
Entering of the city block map
The aim of this process is to enter the spa-
tial data of the city blocks to the proper
data layer. The resulted map is the basis
of other processes of design.
Entering the location of entrance
for the normal consumers
It should be mentioned that the block
map of the city includes only the blocks,
i.e. the space bordered by the streets, and
27G I S D E V E L O P M E N T - M I D D L E E A S TJ A N UA R Y - F E B R UA R Y 2 0 07
Using GIS in
different
stages of
network
design brings
many benefits
FFiigg.. 11 The module developed for the design and extension of the gas
distribution network

3. not the buildings. Therefore, in this
process, the entrance of the gas con-
sumers are located on the boundary of
the city blocks as a point feature, and the
attribute data of the building such as its
landuse and number of floors and resid-
ual units are attached to it.
Entering the location of entrance
for the industrial units
In this process, the locations of the
entrance of industrial units are recorded
on the map as point features, and the
data required for the calculation of the
gas consumption are assigned to them.
Calculation of the maximum
per-hour consumption
The gas consumption of the industrial
units are calculated using a defined
mathematical formula and the primary
data assigned to these features.
Market analysis and predicting the
future consumption characteristics
In this process, a mathematical model is
used to predict the maximum per-hour
consumption for the normal gas con-
sumers in the future. In this model, the
prediction is done on basis of the predic-
tion coefficients, building attribute data,
present consumption values, and other
relevant data available in GIS layers.
In addition to the prediction of the
future consumption, the general con-
sumption of the city, and the needed
number of TBS stations are calculated in
this process. At the end of this process
the resulted map of market analysis is
completed and sent to the next unit.
Deciding on the location of
branching points
The network control unit is responsible
for deciding on the location of any
required branching. Such a branching is
needed for extension of the network for a
new region. The location of the branching
depends on the estimated consumption
of the region and the location of the net-
work lines in the area.
Zoning of the city
In this process, areas with a maximum
consumption of 45000 cubic meter per-
hour are selected and considered as gas
distribution zones. For any such a select-
ed zone, the software calculates and
reports the maximum consumption.
Defining the distribution districts
A selected portion of a zone with a maxi-
mum consumption of 5000 to 10000
cubic meter per-hour is considered as a
gas distribution district. Design of the dis-
tribution network of any district is car-
ried out separately, considering a unique
TBS station for each district.
Defining location of TBS station
Site selection of the TBS station for any
district is done, considering different
parameters.
These parameters include the distance
to the network lines, distance to the main
consumption points, distance to the high
building and electrical posts, and avail-
ability of a vacant land with dimensions
of at least 13x17 meters.
Designing, drawing main and bran-
ching lines, entering attribute data
In this process, the network designer
defines the location of the main and
branching lines according to some
parameters and regulations. The location
of these lines along with other decided
factors such as the type and diameter of
the pipes are entered and stored in the
Geodatabase. Using of the available tools
28 G I S D E V E L O P M E N T - M I D D L E E A S T J A N UA R Y - F E B R UA R Y 2 0 07
FFiigg.. 22 Topological relations in “Node-Matrix” and “Link-Matrix”, as required by the “GPNET”

4. of the system, this process can be done
easily and smoothly.
Defining the location of the
network main and 63mm nodes
The network designer determines the
location of the required nodes on the
main and branching lines of the network
according to the structure of the network
lines. The location of these nodes and
lines are used to calculate the overall load
of each main node and to prepare the
node-structure map.
Assigning the industry consump-
tion loads to nearest main node
Using this process, the consumption load
of any industrial unit is automatically
assigned to its nearest node. In addition,
the lines connecting the industrial unit to
its nearest node are drawn.
Assigning loads of normal con-
sumers to their adjacent network
Having the search distance defined, the
gas consumption of each unit is automat-
ically assigned to its nearest or adjacent
line (main line or 63mm branch lines).
The final result of this process is the
determination of the number of con-
sumers and the overall load of each net-
work line. Moreover, using this facility,
the 25 mm branches are automatically
drawn connecting each consumer to its
nearest line.
Calculating consumption load, num-
ber of consumers for each node
Using this process, for any 63mm second-
ary node, all its branched lines are identi-
fied. Then, the overall number of con-
sumers connected to these lines and the
overall gas consumption of the lines are
assigned to the node. This resulted infor-
mation is stored in a table for all the
63mm nodes. This table is used for con-
trolling and evaluating designed branch-
ing structure according to some regula-
tions regarding the consumption loads.
Assigning the load of the nodes to
the main network lines
For any main line in the network, the con-
nected 63mm nodes are identified and
the consumer numbers and consumption
loads for all nodes are added up and
assigned to the main line.
Generation of node-structure map
The topological relations between the
main nodes and lines of the network are
calculated and stored in the format of
“Node-Matrix” and “Link-Matrix”, as
required by the “GPNET” software. This
software is used for hydraulic calcula-
tions of designed distribution network.
Figure 3 shows the resulted matrixes.
It should be mentioned that, as an
accepted tradition in the gas distribution
network, the load of a main line is
assigned to its end node.
Integration of GIS with “GPNET”
software for hydraulic calculations
In this process, the two software are con-
nected using a loosely coupling approach.
In other words, using the data sharing, a
simply integrated system is resulted.
Information about the topology of the
network is stored in “EXCEL” format to be
used by “GPNET”. On the other hand, the
results of the hydraulic calculations,
including the pressure and speed of the
gas flow in nodes, are stored in “EXCEL”
format and returned to GIS. These results
are assigned to the nodes in GIS.
Evaluating the reliability and
balance of the network
The reliability and robustness of the net-
work is analyzed using the hydraulic cal-
culation results. By designing multiple
networks for a town, as different design
scenarios, and analyzing their reliability
and robustness, the optimum network
will be selected. The parameters and cri-
teria for evaluating the reliability and
robustness of the network are developed
and implemented in the system.
If the criteria are not satisfied in a node,
the node is highlighted by GIS and the
designer is prompted to change and cor-
rect the network and repeating the proce-
dure. Correcting the network is usually
done using one or some of the followings:
changing the diameter of the main lines,
changing the structure and combination
of the network by removing and/or
adding some lines, altering the location
of the TBS stations, changing the location
of branch lines and changing the load dis-
tribution structure on the network lines.
Defining the location of the valves
on the mail lines and branch lines
This process provides designer with some
tools to define location of valves accord-
ing to some defined criteria, regulations.
Detailed design of the network
This facility provides proper tools for
entering, storing, retrieving and visualiz-
ing all the components of the network,
like equal tee, non-equal tee, cap, reducer,
60 degree elbow, 90 degree elbow, etc.
Storage and using of cathodic-pro-
tection unit information
This facility is a collection of tools needed
by the engineers of the cathodic-protec-
tion unit for entering, storing and retriev-
ing of data.
29J A N UA R Y - F E B R UA R Y 2 0 07 G I S @ D E V E L O P M E N T - M I D D L E E A S T
Conceptual
model was
made using
capabilities of
Geodatabase,
Geometric-
Network,UML

5. Preparing the list of assets used
This facility provides the designer with
the ability to calculate the amounts of
physical assets used in the network
according to proper measurement units
and classified by the size and type of the
assets.
Using these lists, the cost of implement-
ing the network is calculated. The design-
er could design different scenarios and
decide on the optimum design consider-
ing both the network reliability and the
cost as selection criteria.
Scheduling project implementation
This facility enables the designer to man-
age and monitor the progress of the proj-
ect according to the time table and to
visualize the steps of the project progress
on a map along with other data such as
the area covered in each stage.
Issuing of customer identification
codes
In this process, different tools are used to
edit and visualize the consumer (cus-
tomer) information and to assign new
codes to the new customers.
Defining gas flow directions
During this process, the gas flow direc-
tions will be defined by operator for the
whole network. Analysis and processes in
the network, such
as the event man-
agement, need
the flow direc-
tions.
Defining the
valve to stop
gas flow
The management
and response to
the unwanted
events is among
the most impor-
tant aspects of the
network manage-
ment. In this process, first the location of
the consumer reporting the event is
defined, using the recorded location of his
telephone number. Then, using network
analysis, the valve that should be blocked
to cut off the consumer is defined and its
location is reported.
Defining the cut off consumers
The aim of this process is to define the
consumers that will be cut off when a
valve is closed. Using this facility, the
location of all cut off consumers are
defined and shown on the map with a list
of their addresses and telephone num-
bers . This list will be used for informing
such consumers about the time and dura-
tion of the flow blockage.
In addition, this process can be used by
designers to design branching lines and
location of the valves in the network.
By closing a valve, the number of cut
off consumers and their consumption
load will be determined, which can be
used to decide on the location of the
valves.
CONCLUSION
The design of gas distribution network
needs a variety of spatial data and analy-
sis. Many of such analysis tools are
already available in a standard GIS soft-
ware such as ArcGIS.
However, a multi-purpose GIS software
cannot be easily used by the network
designers. In addition, many of the
processes in network design need func-
tionalities that are not available in nor-
mal GIS software.
To overcome such shortcomings,
required functionalities were developed
and added to the system by program-
ming by using ArcObjects. In addition, a
hydraulic software is linked to GIS to per-
form required hydraulic calculations. The
resulted system can be considered as a
simple spatial decision support system.
Using the system, a designer can follow a
sequence of processes to come up with
the optimal design.
In the sequence of the processes, the
result of selecting any alternative can be
tested and visualized. Using the system,
shortcomings and deficiencies of design
can be identified and proper changes in
the setting can be made to improve the
design.
In general the system is capable of mar-
ket analysis, node-map generation,
hydraulic calculation, design reliability
evaluation, helping the workflow man-
agement, and the event/crisis manage-
ment. Moreover, the system can be used
for spatial data management, including
editing, updating, storing and visualizing
of both data and analysis of results.
30 G I S D E V E L O P M E N T - M I D D L E E A S T J A N UA R Y - F E B R UA R Y 2 0 07
Saadi Mesgari
smesgari@yahoo.com
Reza Nourjou
Rezan2996@yahoo.com
Hossein Aghamohammadi
hossein.aghamohammadi@gmail.com
GIS group, Faculty of Geodesy
and Geomatics
K.N. Toosi University of
Technology, Tehran, Iran.
FFiigg.. 33 Topological relations in “Node-Matrix” and “Link-Matrix”, as
required by the “GPNET”