The Why & How of Natural Gas Pipelines
A key element of setting up a successful natural gas infrastructure would be the installation of a network of pipelines. Pipelines are essential to carry natural gas from the source of origin to various points of distribution. The first natural gas pipeline was installed in 1891 in United States. It was used to transport natural gas from the gas wells in central Indiana to Chicago.
The 120-mile pipeline was basic and rather inefficient. However, it did mark a milestone in the development of the national gas industry. Prior to this, there was no way to transport natural gas from its source to areas that needed energy supplies. Most of the natural gas produced in the early days was simply vented off. Other fossil fuels like coal that could be easily transported were preferred.
The growing popularity of pipelines in the 1920s helped harness and use valuable natural gas. After the 2nd World War, the United States concentrated on setting up a natural gas infrastructure and soon had a well developed pipeline network that distributed the resource to homes, commercial establishments and industries across the country.
With energy experts acknowledging that pipelines are economical, convenient and safe, today we have natural gas pipelines transporting this clean energy over continents and under seas.
The Basic Types of Pipelines
A natural gas pipeline system has several kinds of pipelines. Each of them serves a different purpose and will carry gas of varying pressures. The closer the pipeline is to a customer, the lower will be the pressure of the gas and the smaller the pipe diameter.
Gathering System of Pipelines: The gathering system of pipelines starts at the wellhead. Normally, there are whole networks of gathering pipelines that carry gas from the source of origin to either another set of pipelines or to a centralised processing facility. They normally travel a short distance and are small diameter pipes that are buried around four feet under the ground. Some of the wells from which natural gas is extracted may have high levels of carbon-di-oxide and sulphur. This kind of gas quality is described as sour gas and requires a special kind of gathering pipeline as it is highly corrosive.
Transmission System of Pipelines: Natural gas moves from the gathering pipelines to the transmission pipelines. The transmission system consists of intrastate as well as interstate pipelines. As the name suggests, the interstate pipelines travel across state boundaries and sometimes, even across countries. The intrastate transmission pipelines describe the network within a state’s boundaries.
The main function of the transmission lines is to distribute huge volumes of gas over long distances to local distributing companies. The mainline transmission lines are between 16 and 48 inches in diameter and are normally made of steel. They carry gas at pressures ranging from 200 to 1200 pounds per square inch (psi). But the pipelines are made to withstand much higher pressure. Those pipelines that are installed in heavily populated areas are normally capable of carrying double the pressure of gas than they actually do.
The transmission system will have compression stations at regular intervals in order to boost the gas pressure if needed.
Distribution System of Pipelines: Distribution pipelines are made of steel, plastic or even copper. They are the link between the high pressure transmission lines and the low pressure service lines. The distribution lines may range from 2-24 inches in diameter. The pressure within the distribution system is controlled by regulators and the gas operates at different pressures in different sections of the distribution system. Normally, a distribution system will also have relief valves which will vent off gas harmlessly in case there is a pressure build-up.
Service System of Pipelines: The service line is the natural gas pipeline that actually supplies gas to homes and businesses. Made of plastic, they have a maximum diameter of an inch. Gas flows through the pipes at extremely low pressures. Once the gas passes through the gas meter, it becomes the property of the consumer. When a consumer switches on the gas stove, the gas pressure will be slightly higher than the air pressure. This causes the gas to flow out. It is then ignited by the consumer for various purposes like cooking and heating.