City gas distribution (CGD) is a growing sector and it aims to provide uninterrupted gas supply to domestic, commercial and industrial customers in the form of piped natural gas (PNG) and compressed natural gas (CNG). This pipeline system transports and distributes gas to consumers. The distribution system involves gas distribution mains and service lines. Once the network has been set up, there is a need to ensure continuous availability of gas to consumers and maintain the health of the pipeline system. However, maintaining network integrity and reducing the operations and maintenance (O&M) cost remain a major challenge for CGD entities.
Pipeline integrity management
The integrity of pipelines is a basic concern for pipeline operators. Therefore, the ability to detect anomalies due to corrosion, erosion, milling and mechanical damage is of significant interest to them. Proper pipeline integrity management can not only extend the life of existing pipelines but also help in preventing damage in the future, if undertaken during the design and construction of new pipelines. Over the years, several technologies have been adopted to ensure safety of the gas pipeline network.
Gas leakage is a hazard that can result in major accidents involving human injuries and fires, as well as have a huge impact in terms of the costs involved. To avoid such situations, preventive inspections are of paramount importance. Since gas leakage is not visible (the radiation emitted by gases is invisible to the human eye), thermal imaging technology is used to detect and evaluate the severity of leakages. Over the years, thermal imaging technology has evolved to a great extent. The thermal cameras capture the infrared radiation emitted by various materials, transform them into electric signals, and then convert these into video signals. Thus, thermal cameras convert invisible infrared radiation into a visible image. With regard to the oil and gas sector, this technology can be used extensively for predictive maintenance, fire prevention, firefighting, flare monitoring, tank level detection and infrared windows. The clear benefits of this technology are substantial cost savings, increased worker safety, and enhanced product and process quality.
Additionally, large manufacturing and industrial facilities have been deploying fire suppression products at higher rates over the years. With regard to the oil and gas industry, the market for fire suppressants using clean agents is expected to grow in the future as these have been specifically developed to combine performance, safety and ease of handling with an excellent environmental profile.
In order to mitigate threats to its pipeline integrity, Indraprastha Gas Limited (IGL) continuously monitors the pipe to soil potential of its pipeline network through a GSM-enabled device. Further, close-interval potential surveys and direct current voltage gradient surveys are also carried out to check the health of pipelines. Other methods adopted by IGL for its pipeline integrity management include internal corrosion monitoring through an electrical resistance probe, ultrasonic thickness measurement and magnetic tomography. Magnetic tomography locates stress-causing defects in a pipeline, identifying structural defects that could exist under a healthy coating.
CGD entities face several challenges while carrying out O&M of their networks. These are third-party digging, emergency handling, maintenance of healthy systems, and gas losses in CNG and PNG networks. One of the major safety issues in the PNG segment is the damage caused to the CGD network by third parties. Third-party excavation where a CGD network has been laid creates problems in gas transmission and stops the supply to various households. Usually, the same route is used for water pipelines, telephone wiring, cable lines, etc. In order to tackle this problem, there is a need to work in coordination with other utilities and ensure that the groundwork is synchronised with the plans drawn up. With the objective of mitigating the chances of damage due to third-party damage, IGL has installed pipeline markers at every 50 metre against the T4S requirement of 100 metre.
Further, it holds regular meetings with third-party agencies and has taken steps for spreading general awareness through SMSs, radio advertisements and liaison meetings with resident welfare associations. In an attempt to minimise response time, the third parties can pass on the information of digging activities to IGL through their “IGL-Connect” mobile application and “Dial-Before-Dig” tab on the website.
Another major challenge with regard to O&M of PNG systems is handling emergency situations arising on account of gas leak due to pipeline damage, fire due to gas leak, or tripping of field regulating stations (FRS) causing stoppage of gas supply. In such scenarios, passing information to customers and isolation of the affected network is of paramount importance. To handle such situations, a national toll free number has been introduced, on which any person can inform about the leakage. Further, information about an interruption in the PNG supply with the expected resumption time is provided to the customers through SMS.
IGL has taken several mitigation measures for identification and rectification of leakages. These are odorisation of natural gas; foot patrolling over pipeline network using laser detectors; pressure testing of pipeline network in sections; daily monitoring of gas inflow and outflow in the network between city gate stations, CNG stations and FRS; and daily monitoring of gas outflow from FRS with respect to the estimated downstream consumption.
In the past, CGD entities deployed information technology (IT) and operational technology (OT) solutions as two separate domains. However, the convergence of IT and OT has helped CGD players reduce costs and risks, as well as enhance performance. Currently, various technologies have been introduced for carrying out O&M works of CGD networks. Geographic information system (GIS)-based infrastructure has been put in place, and several types of control systems and associated solutions such as supervisory control and data acquisition (SCADA), distributed control systems and other smaller control system configurations have been introduced.
The SCADA system offers several advantages. Chief among these are real-time monitoring of gas consumption, reduction in data errors, and automation of processes. Also, enterprise resource planning is being used to record and process the available data. Different cloud-based applications are also being used by CGD companies to integrate the available technologies and take proactive measures.
IT and OT technologies help in optimising and controlling industrial processes, tracking asset performance and monitoring quality. These help in reducing costs and risks by capturing the operational history. Further, they facilitate condition and risk-based maintenance, and enable the adjustment of production in line with the future demand. The optimisation and control of industrial processes brought about by these technologies result in the effective functioning of field personnel.
With regard to IGL, GIS mapping has already been started and nearly 80 per cent of data capturing has been completed. Further, SCADA is being used on a pilot basis for remote operation of valves and prepaid meters have also been installed on a pilot basis in Rewari. While around 2,200 AMR meters are functional for the past seven years, 6,000 more were installed in 2017-18.
The way forward
With importance being given to the development of the CGD segment by both the government and industry players, there is a need to work towards addressing the challenges being faced with regard to O&M and pipeline integrity management of CGD networks. These can be tackled by deploying smart technologies, effectively implementing IMS, ensuring strict compliance with T4S norms, and increasing the coordination between different utilities. In order to ensure safety at all times, there is a need for continuous monitoring and review. These tools not only help to enhance the effectiveness of the present system but also facilitate the design and implementation of future systems in a better manner.
Based on a presentation by Vikas Bansal, AGM (PNG Projects and O&M), Indraprastha Gas Limited at ISGW 2018