[Mako19]

I found the information pasted below in some old emails between my Dad and me when we were researching gas pipelines to figure out what type and size of pipeline was going on his land and what the operating pressure would be.

You can go to the links and find much more information. What you see below is just what I copied and pasted to email to my dad.

[SIZE=3]The Transmission System[/SIZE]
From the gathering system, the natural gas moves into the transmission system, which is composed of about 272,000 miles of high-strength steel pipe ranging from 20 inches to 42 inches in diameter.
These large transmission lines for natural gas can be compared to the nation's interstate highway system for cars. They move large amounts of natural gas thousands of miles from the producing regions to local distribution companies (LDCs). The pressure of gas in each section of line typically ranges from 200 pounds to 1,500 pounds per square inch, depending on the type of area in which the pipeline is operating. As a safety measure, pipelines are designed and constructed to handle much more pressure than is ever actually reached in the system. For example, pipelines in more populated areas operate at less than one-half of their design pressure level.
Many major interstate pipelines are "looped" -- there are two or more lines running parallel to each other in the same right of way. This provides maximum capacity during periods of peak demand. The pipeline rights of way are usually 100 feet wide and are leased from landowners with restrictions on construction activities to minimize the potential for accidental damage.
The Distribution System

From the gate station, natural gas moves into distribution lines or "mains" that range from 2 inches to more than 24 inches in diameter. Within each distribution system, there are sections that operate at different pressures, with regulators controlling the pressure. Some regulators are remotely controlled by the utility to change pressures in parts of the system to optimize efficiency. Generally speaking, the closer natural gas gets to a customer, the smaller the pipe diameter is and the lower the pressure is.
The gas utility's central control center continuously monitors flow rates and pressures at various points in its system. The operators must ensure that the gas reaches each customer with sufficient flow rate and pressure to fuel equipment and appliances. They also ensure that the pressures stay below the maximum pressure for each segment of the system. Distribution lines typically operate at less than one-fifth of their design pressure.
As gas flows through the system, regulators control the flow from higher to lower pressures. If a regulator senses that the pressure has dropped below a set point it will open accordingly to allow more gas to flow. Conversely, when pressure rises above a set point, the regulator will close to adjust. As an added safety feature, relief valves are installed on pipelines to vent gas harmlessly, if a line becomes overpressured and the regulators malfunction.
Sophisticated computer programs are used to evaluate the delivery capacity of the network and to ensure that all customers receive adequate supplies of gas at or above the minimum pressure level required by their gas appliances.
Distribution mains are interconnected in multiple grid patterns with strategically located shut-off valves, so the utility can perform maintenance of its lines without ever shutting off a customer.
http://www.aga.org/Kc/aboutnaturalgas/consumerinfo/Pages/NGDeliverySystem.aspx

Also, need to find out which one of these you have:
[SIZE=3]“Natural gas travels from the wellhead to end consumers through a series of pipelines. These pipelines -- including flowlines, gathering lines, transmission lines, distribution lines, and service lines -- carry gas at varying rates of pressure. [/SIZE]
[SIZE=3]The higher the pressure of gas in a pipeline, the more potentially dangerous an accident with that pipeline could be. “[/SIZE]
[SIZE=3]3) Transmission Pipelines[/SIZE]
[SIZE=3]Purpose: Transmission pipelines carry natural gas across long distances and occasionally across interstate boundaries, usually to and from compressors or to a distribution center or storage facility. [/SIZE]
[SIZE=3]Description: Transmission lines are large steel pipes (usually 2" to 42" in diameter; most often more than 10" diameter) that are federally regulated. They carry unodorized gas at a pressure of approximately 200 to 1,200 psi. [/SIZE]
[SIZE=3]Special considerations: Transmission pipelines can fail due to: seam failures, corrosion, materials failure, or defective welding. [/SIZE]
4) Distribution Pipelines
Purpose: Distribution pipelines, also known as "mains," are the middle step between high pressure transmission lines and low pressure service lines. Distribution pipelines operate at an intermediate pressure.
Description: Distribution pipelines are small to medium sized pipes (2" to 24" in diameter) that are federally regulated and carry odorized gas at varying pressure levels, from as little as 0.3 up to 200 psi. Distribution pipelines typically operate below their carrying capacity. Distribution pipelines are made from a variety of materials, including steel, cast iron, plastic, and occasionally copper. (What type of pipe? Material? Grade? Wall Thickness?)
http://energy.about.com/od/drilling/a/5-Types-Of-Natural-Gas-Pipelines.htm