The world is largely dependent upon natural gas for various purposes. Natural gas is one of the essential energy resources, and the world consumes 132,290,211 million cubic feet (MMcf) of natural gas per year as of the year 2017.
Ever wondered how natural gas transported throughout the world is? As natural gas is inflammable, it is important that it is safely transported to the destination. To summarize the natural gas process in three steps:
After the production process, the gas is brought to the surface to make it stable for transport. The natural gas is then transported through international pipelines or through cargo ships.
Types of Pipelines
· Gathering system
· International pipeline system
· Distribution system
Classification of Pipelines
Pipelines can also be classified into two types:
Interstate: Similar to a highway, an interstate pipeline carries natural gas across state boundaries or sometimes across countries as well
Intrastate: these pipelines transport natural gas within a particular state.
Components of Pipelines
Interstate pipelines are essential as they carry most of the essential gas 24 hours a day. To ensure that the transportation is done efficiently and effectively, there are multiple components of pipelines that must be maintained, and quality assured.
Gas transmission pipelines can range from 6 inches to 48 inches, based on the purpose and functionality. There are certain pipes that are as small as 0.5 inches in diameter, but those are usually for gatherings and distribution.
However, the main transmission line is usually between 16-48 inches range, also called mainline transmission pipeline. The pipelines that deliver to and fro mainline pipes are called lateral pipelines have a diameter of 6-16 inches.
The major pipelines of the interstate are between 24-26 inch diameters. The line pipe consists of strong carbon steel material as per the standards of the American Petroleum Institute (API). There are also some pipelines made of highly advanced plastic serving versatility to improve efficiency.
Production of these pipelines is done in steel mills which solely work of producing these pipelines. Depending upon the diameter of the pipelines, the production process varies.
There are two types of techniques; for larger diameter pipelines, such as anywhere between a range of 20-20 inches diameter, sheets of metal are used to create a tube shape that has the ends welded together to create a pipe. However, the other method or smaller pipes includes heating metal bars and punching a hollow tube inside to create a pipe structure. The pipes are always tested before sending out to check for any defects or faults.
Pipelines are then covered with a coating to prevent corrosion once placed underground. This coating helps in the protection of these pipes from moisture which can damage them. Previously pipes were coated with specialized coal tar enamel, but now they are mostly covered with a fusion bond epoxy.
Natural gas is noticeably pressurized as it travels through an interstate pipeline, and to ensure the desired pressure, compression of gas along the pipeline is required. Compressor stations are used to ensure this pressure and are usually located at 40-100 miles intervals along the pipeline.
After the gas enters the compressor station, it is then compressed by either a turbine, motor, or engine. The turbine compressors use natural gas to gain energy as it compresses it. At the same time, some compressor stations operate on electricity rather than using natural gas.
Metering stations are also positioned along interstate natural gas pipelines. These stations are used by companies to check the natural flow of gas in the pipelines.
The metering stations track the glow of natural gas and help the companies to keep a record along the pipeline. Special meters are used to track and monitor the flow of gas through pipelines without causing any hurdle in the movement.
Valves are also essential for the flow of natural gas through pipelines. There are several valves located throughout the pipeline. The valves act as a gateway where they control the flow of gas; it can either be open to allow the gas flow or can be closed to stop the gas flow.
You can close the valve for various reasons such as maintenance or replacement of pipes or for any safety purposes as well. The range for valves is usually between 5-20 miles along the pipelines.
Control Stations and SCADA Systems
There are customers on both ends of a pipeline. One end is the producing end, while the other is the consuming end, which can use gas with a gas safety certificate. The producers input the gas from one end while the consumers use that gas on the other end.
Control stations are built to ensure that the gas enters the pipeline seamlessly and is distributed accurately on the other end. These control stations monitor the quality and execution of operations that are necessary for the process of delivering natural gas.
These control stations collect, assimilate, and manage data received from monitoring and compressor stations all along the pipe. The data received by a control station is provided by Supervisory Control and Data Acquisition (SCADA) systems. These systems collect accurate data throughout the pipelines using valves and meters to ensure the safety and seamlessness that is important for quality control.
Pipeline Inspection and Safety
To ensure the safe and smooth execution of gas transportation, pipeline companies routinely inspect their pipelines for corrosion and defects. These defects are tested using equipment known as 'smart pigs.' The robotic instrument is placed into the pipelines to check the interior of a pipe.
The smart pigs are used to check:
· Signs of corrosion,
· Detect minute leaks
· Any other defect
Placing a smart pig down a pipeline is also known as 'pigging' the pipeline. This helps in identifying any defect or issue in the pipeline that can then be fixed using proper methods. It is an efficient way to check what is going on inside of the pipelines. It is important to have a thorough check on these pipelines for smooth transportation of gas.