The major constituents of a city gas distribution (CGD) network are sub-transmission lines, city gate stations, odorisation systems, a primary network of steel pipelines connecting city gate stations to various district regulating stations, a secondary system consisting of medium density polyethylene pipelines and tertiary networks comprising polyethylene pipes, galvanised iron and copper tubes as well as isolation valves. Further, the network also comprises industrial pressure regulating stations, common pressure regulating stations and metering stations. Once the network has been set up, there is a need not only to ensure the continuous availability of gas to consumers but also to maintain the health of the pipeline system. The operations and maintenance (O&M) of the distribution network poses a great challenge as the safety of the system and the surrounding areas is of paramount importance.
Effective implementation of IMS and T4S
As per the regulations and acts formulated by the Petroleum and Natural Gas Regulatory Board, CGD networks are required to have an appropriate integrity management system (IMS) in place and comply with T4S safety standards. The IMS includes the formulation of an integrity management plan, performance evaluation of the plan, a communication plan, the management of change resulting from actions of third parties, and quality control.
In the initial stage of managing a CGD network, all the relevant data needs to be gathered and reviewed for the identification of threats. After the evaluation process, the impact and consequences of the threats are analysed and a proper risk assessment for identifying the operational and business risks is carried out. This is followed by an integrity assessment analysis whereby the mitigation and response strategies are decided upon and taken up. Finally, the data needs to be upgraded and integrated in accordance with the outcome of the analysis carried out.
There are three major categories of challenges faced while carrying out O&M of CGD networks. These are safety issues in the piped natural gas (PNG)/compressed natural gas (CNG) segment, 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. In contrast to cross-country pipelines, which are typically straight, a city gas pipeline network is complicated and has several branches. 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. Further, the widening of roads across cities also creates difficulties in
line tracing and repairing. In some cities, the unauthorised modification of piping by customers has also been observed. This poor quality of work enhances the risk of leakage. Therefore, there is a need to introduce a mechanism for keeping these things in check. Further, PNG contractors often have a delayed response in terms of repairing the pipes despite the presence of emergency response vehicles and teams.
With regard to safety in the CNG segment, forecourt management is of the utmost importance. In order to maintain healthy systems, periodic testing of cylinders is required. Dedicated teams need to be set up to ensure that duly tested cylinders are put to use in the vehicles. There needs to be a greater thrust on the calibration of meters in compressors and dispensers in order to minimise the gap between the amount of gas purchased by suppliers and that sold to consumers as well as to tackle the loss of unaccounted-for gas. Further, an effective mechanism needs to be put in place to ensure safe dispensing of CNG. Lastly, there is a need for proper monitoring while filling and decanting of cascades mounted on light commercial vehicles. Further, the difficulties in identification of gas leakages in high-rise buildings should be dealt with and the damages resulting from actions of third parties should be curbed. Also, there is a need to bring about reconciliation of gas using smart metering systems and automation of CNG dispensing mechanisms.
IT and OT solutions for automation
In the past, CGD entities deployed information technology (IT) and operational technology (OT) solutions as two separate domains. However, over the years, the convergence of IT and OT has helped CGD players in reducing costs and risks as well as enhancing 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 also 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, process efficiency and monitoring quality. These help in reducing costs and risks by capturing the operational history. Further, they facilitate condition and risk-based maintenance, and further 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 effective functioning of field personnel. However, there are certain challenges with regard to IT-OT convergence for the CGD segment. First, technical limitations have prevented the sharing of resources and other available infrastructure. From an organisational perspective, IT and OT groups have traditionally had different reporting structures, objectives and functions. While a certain level of progress has been achieved, the convergence of operational and information technology across industry and infrastructure is not yet complete.
Globally, GIS is being used for managing, maintaining, repairing and inspecting CGD networks. Data management of network elements, management of attribute information, procuring geospatial information, creation of summarised statistical reports, temporal management and monitoring for timely inspection, maintenance and repairs is being practised. Further, several emergency handling measures such as identification of the affected area for isolation, shutting down of the valves of the isolated areas and alerting the emergency response team have been put in place.
The way forward
With the importance being given to the development of the CGD segment by the government and industry players, there is a need to work towards addressing the challenges being faced with regard to the O&M of CGD networks. These can be tackled by the implementation of smart metering systems, proper and timely calibration of meters, use of smart technologies, effective implementation of IMS and strict compliance with T4S norms. Ensuring safety at all times calls for continuous monitoring and review of and improvements in the system. 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 Jiledar, Managing Director, Green Gas Limited, at a recent India Infrastructure conference