Pipeline systems are the most reliable means for delivering hydrocarbon products; an important energy source. They do this safely and efficiently 24 hours a day 365 days a year.
Transportation of natural gas from wellheads to the final consumer falls into three categories:
- Gathering System: Low-pressure transportation of raw natural gas from wellheads to processing plants. Gathering systems use small-diameter pipes either directly to the plants or a larger interconnecting mainline pipeline.
- Transmission System: High-pressure transportation of natural gas from processing plants to distribution centers or storage facilities. Transmission systems use large-diameter pipes (12–48 inches) to transport gas either within states (intrastate) or across state lines (interstate).
- Distribution System: Low-pressure delivery of natural gas to consumers. Natural gas flows into small diameter pipelines (2–16 inches)-mains, and into smaller diameter pipelines (½–1½ inches)-services. Services go directly into homes and buildings.
Interstate natural gas pipeline systems consist of many components. They make up the systems and ensure efficient and reliable operations. The major components include:
Pipes
The majority of natural gas pipelines in the United States is transported using pipes made from carbon steel pipes. The pipes are engineered to meet strength and durability standards set by the American Petroleum Institute (API). They must have high strength and durability to withstand high pressure. API is a trade association representing the oil and gas industry.
Compressor Stations
Interstate transmission pipelines transport natural gas over extended distances. Distance, elevation difference as well as friction slows the movement of natural gas and reduces the pressure within the pipeline. It needs a ‘boost’ to continue with the journey.
Compressors stations are pipeline system components that are vital to the natural gas transportation process. They are built along the pipeline and used to compress the gas, to a specified pressure, to ensure continuous flow downstream. Compressor stations increase the pressure of the gas at the discharge side compared to the intake side. They are usually placed at 40 to 100 miles intervals depending on the terrain and capacity of the pipeline. Compressor stations operate around the clock.
Valves
Valves are important components for the safe operations of pipeline systems. They are used for diversion, cut-off, throttling, check and overflow pressure relief. Valves along pipeline systems are normally open. They are closed when a section of the pipeline needs to be isolated either for routine maintenance or emergency shut down.
The most common valves used in pipeline systems include:
- Ball valves
- Gate valves
- Check valves
- Plug valves
Placement of valves along interstate pipeline systems is subject to regulations by safety codes. This is to minimize any environmental and other impacts in case of an accident.
Metering Stations
Natural gas pipeline system operators want to continuously know the flow rate of the gas. Knowing the amount of gas flowing is vital in preventing public and environmental safety issues. Operators also use this information to make sure their customers receive the right amount of gas they pay for.
Meter stations are placed along pipeline systems to monitor the flow of natural gas. They are also placed at locations where gas custody transfer takes place to provide accurate value when natural gas is being sold or purchased. The measured value can be in small quantiles or it can be summed up over a specific period of time. Meter stations measure the flow rate of natural gas without impeding its movement.
Conclusion
These are the major components that play a critical role in transporting natural gas from processing regions to consuming regions. There are also other ‘supporting’ components, like control stations and sensors, that enhance the efficiency, integrity and safety of natural gas transportation.
