Geographic information systems (GIS) are tools for capturing, storing, analysing and presenting all types of spatial and geographical data. These systems play a crucial role in city gas distribution (CGD) and assist utilities in planning, designing and improving operational efficiency. They also add value to the CGD business by facilitating integration with other business systems. Integrating GIS with mainstream CGD processes leads to improvements in analyses, visualisation and network planning, as well as informed decision-making.
City gas GIS consists of spatial data and attribute data. The former refers to the position of geographical entities and their relations, including basic geographical data and the measurement data of pipelines. It reflects spatial locations and the topological relationships between gas pipelines, equipment and facilities.
Attribute data describes information like material diameters and pressure levels. It includes forms, documents, multimedia and other information. The relationship between spatial data and the associated attribute data is established through the keyword ID. Basic geographical data is stored with the client, and pipeline data is stored in the server to improve the speed of data enquiries and searches. The data is stored in layers so it can be conveniently updated, maintained and managed as required. In a layered data format, geometric characteristic symbols like points, lines and surfaces are considered in a comprehensive way, so that the data in each layer has similar geometric characteristic symbols and attribute compositions.
Gas network data includes information on city gate stations, pressure regulator stations, distribution stations, compressed natural gas stations, valves, node connecting devices (diameter changing points, material changing points, three-way valves, cross-junctions and elbows), accessory equipment, and users. Linear elements and pipelines can be divided according to pressure, into low pressure, medium pressure, intermediate pressure or high pressure; or according to material, into steel pipes or polyethylene pipes.
A CGD network is a system of connected pipelines. Its primary assets are the main pipes and service pipes for distributing gas; valves and regulator devices to control and regulate gas flow; and joints, fittings and meters to measure gas inlets and outlets. As compared to power or telecom networks, CGD pipeline networks are characterised by larger investments, lesser flexibility, complex construction structures, and stringent safety requirements.
While planning and designing a CGD network, there is a requirement for demand growth to be projected over a decade to avoid frequent network upgrades, necessitating adequate spare capacity. It is also necessary for service areas of city gas stations and district pressure regulator stations (DPRSs) to be clearly defined so that there are an optimal number of DPRSs. In addition, routes must be identified in such a way that maximum reach can be achieved with minimum length; supply pressures at consumer and intermediate points should not over/undersize any element; and network design times should be minimal.
Leakage management: Valves need to be closed in case of gas accidents, pipeline leaks, valve damage and pressure regulator damage. GIS establishes topological relationships between pipeline sections and points like valves and pressure regulators, and helps identify the nearest valves or structures that must be closed. In the case of multiple gas supplies, valves will need to be closed in a minimum confined area, and points of emergency isolated to prevent gas from escaping.
Risk management: GIS identifies exposed pipes at a particular location. If CGD companies expect the demand for gas to increase at that location, they can make prior plans to replace vulnerable pipes in order to reduce the risk of damage.
Corrosion management: Underground pipelines are generally made of steel and iron and corrode faster than plastic pipelines due to their proximity to earth and associated moisture. If a pipeline segment is made of steel, it may need to be cathodically protected. Such segments need to be identified. GIS can visually display pipeline segments that have or have not been covered by cathodic protection to help distribution agencies make appropriate arrangements.
Data collection, processing and analysis: City gas pipeline data contains information on geographical features, measurement information, attributes and parameters, photographs and videos (field photographs, videos of equipment in operation, etc.). GIS applications offer external importing tools and are a flexible, convenient and effective instrument for drawing functions of gas networks and facilities as well as editing and processing them. Pipeline information can easily be input and managed through the editing and operating functions to attribute data and ensure that the pipeline and facilities correspond to predefined parameters. Before feeding it into the database, it is important to verify all pipeline data as well as the logical consistency and integrity of gas network data. GIS can also help generate comprehensive charts according to user requirements. Drawings of as-built pipelines, pipeline combinations, partial enlargement and cross- and vertical sections can be mapped, and outputs for pipeline construction and technological transformation can be deduced.
Seamless interoperability with other IT tools: Traditional GIS can be integrated with other business applications like engineering management tools, mobile workforce management systems, outage management systems, supervisory control and data acquisition tools, and analysis tools. GIS can also be integrated with global positioning system (GPS), which is widely used for pipeline patrolling, and rescue and dispatch in gas enterprises. GPS handsets are used to assist pipeline patrols, dynamically display positions and make real-time records. They are also used to give directions for searching pipelines and regulate equipment and valve wells.
Integrated GIS builds seamless interoperability among systems for sharing data and services. For instance, if a new pipeline is to be laid, its design can be prepared using GIS and used by field engineers during site inspections. This has increased the acceptability of web publishing technology for sharing data and publishing field data.
There is an increasing need for integrated GIS solutions in gas distribution as they enable gas utilities to share information about mains, services and cathodic sections instantly and seamlessly across enterprises. This helps in planning for safety systems like cathodic protection for new pipelines and in locating all assets. There is also an increasing requirement for a common workflow across various departments. This has resulted in the integration of GIS with in-house dedicated systems. The integration of GIS with operational support and service delivery applications enables gas distribution utilities to manage, plan, design, construct, operate and maintain networks and carry out risk and emergency response functions more efficiently in a relatively shorter period of time.
Spatial enquiry and analysis: There are different ways of conducting spatial enquiries: fixed-point enquiries, range enquiries, condition enquiries, and others.
In fixed-point enquiries, the attribution information of all objects on current position, pipelines and pipe points with appointed attribution (such as road names, diameter and material) is acquired by viewing the pipeline map. In range enquiries, if a certain spatial range of graphics is chosen on the pipeline map, the selected graphic object is highlighted and the attribute information listed. In condition enquiries, the system provides flexible SQL enquiries and consumers can enquire about the attribute words of pipeline under flexible enquiry conditions.
The poor availability of network records is one of the challenges faced by CGD utilities. Hard copy drawings of networks need to be updated before they are incorporated in GIS set-ups. In addition, base maps need to be accurate to reflect the real position of the network. Another challenge that companies face is in training their employees to use GIS software efficiently.
Physical assets dominate the balance sheets of most utility companies but data deficiencies have often undermined asset management processes. The use of GIS will improve data quality management, assist in quickly identifying issues, and also support their resolution. As the industry matures, the need for GIS in gas distribution is bound to increase. Standards, specifications and technical improvements are constantly evolving to ease and facilitate interoperability between various GIS and non-GIS applications needed by gas utilities. Considering the complex nature of the CGD business and its competitive environment, GIS adoption will help gas utilities improve efficiency in their operations.