What are they made of? I assume some metal of some sort that can withstand being buried for many years. How thick is the metal? obvously thick enough to support the pressures needed, but how thick is that? How big are they…are they just a couple inches across, or are they a few feet across?
By the way, what kind of pressures are we talking about within these pipelines?
Man…too much coffee and not enough things to occupy my mind.
They’re usually made of high strength steel pipe coated by some other stuff that prevents corrosion. Thickness might be something like 1/2 an inch. The really big pipelines (Tennessee Gas Pipeline or Texas Eastern) can be something like 30+ inches in diameter. These transport something like 8 billion cubic feet of gas per day. Operating pressure varies but might be something like 1,000 pounds.
You can learn more by reading up at the FERC (primary regulator) website.
The Texas Eastern pipeline that failed in Edison, NJ in 1994 was a 36" steel pipe, 2/3’s of an inch thick, carrying natural gas at 900 psi. It was 33 years old at the time of failure, and the failure was determined to be caused by a mechanical gouge from an excavator (with nobody from TE watching over construction on their right of way). That pipeline was buried 7 feet underground. I am not aware of any special coating that was on that pipe except for paint.
Back in the 80’s I did summer work at a natural gas compressor station that was then the Michigan-Wisconsin Pipeline Company. There were two 24 inch steel lines coming into the station at around 700psi and going back out at around 1000psi. There were 7 massive engines to drive the compressors but only a few (or sometimes none during the summer when demand was low) would be running at any one time. In addition to the tarry gunk on the pipes they also used cathodic protection to prevent corrosion.
The size and pressure can vary. From 1 in to 48 inch. The San Bruno gas pipe line I bellieve was a 36" pipe when it burst.