Leakproof Pipeline 5

[dik]

Is it possible to construct a pipeline that is reasonably leakproof. Does it have to be exposed, buried, or whatever? The actual construction? materials? single or double wall? monitors for leakage? inspection both during construction and in service? cost? any other issues?


Dik

 

[DerbyLoco]

Hi Big and Little Inches
Thanks for the information about pipeline life expectancy. I also did not know about UK gas not being odourised in the primary network anymore. How would they find a leak if/when external corrosion starts to be an issue and how big would it need to be before it could be detected - much of the pipeline runs through farm land?
When I started work in 1970 the place I served my time at, (International Combustion in Derby), was very busy with North Sea gas work. Mostly rig leg nodes and gas tees plus pig traps. That type of work was a good fit with their main business as boiler makers

 

[BigInch]

The US introduces oderant at the same "town border stations" where gas is metered and sold to local distribution companies. There is no oderant used in cross country USA transmission lines.

The oderizer is mercaptan which contains small amounts of H2S -(forms poisonous, rotten egg smellling and corrosive gas), so H2S is not someting we want in great quantities running around and sticking to the walls of hundreds of thousands of miles of high pressure gas pipelines, so it is left to the last possible point to inject it where the public absolutely needs to be able to detect leaks without the use of complicated equipment that never seems to have its battery charged when you need it.

"He's declaring war on the planet itself."- Vicente Fox

 

[BigInch]

The origin is not clear - some say it was when they sent actual pigs to eat their way out of medieval sewers,

Never heard that particularry British twist on the legend, but I like it. Are you sure it wasn't just a pig's bladder running through the drain pipes. Just saying I find it hard to buy the eating their way out bit, given that pigs do have a finite volume to their stomachs nowhere near what I imagine, has the London sewers. It would take one-heck-of-a-lotta pigs, which I'm sure someone in the middle ages would far rather have seen on their dinner table.

"He's declaring war on the planet itself."- Vicente Fox

 

[LittleInch]

Yeh, I was pretty sceptical as well, but maybe for a small blockage.... ]

The squealing of rubber or leather, especially in gas or air is much more likely.

The other thing about it not being a name but an acronym (it isn't) is that the vast majority of pigs don't inspect anything - they just clean or try and separate.

For separation of products in a pipeline they actually don't do very much at all. I used to work at a multi-product pipeline company who did tests between inserting spheres and pigs to separate batches and no sphere or pig.

They found it made no difference and actually stirred up deposits and basically stopped using them for that purpose. Much of the interface was actually the time taken to open one valve and close the other in the inlet manifold and the mixing of product in the manifold.

Derby Loco - How big - the high pressure system will show up a small hole a lot faster than the low pressure stuff in your street, which is odourised. The change happened in the UK because gas in Europe was never odourised in the high pressure system and when the interconnector between UK and Europe started operation, the UK was exporting gas so they had to change to meet the spec and then had to install hundreds of small odourisation plants at the main offtakes. Helicopter surveys using infrared can find them and the regular ( 5 - 7 year) internal inspections either spot the hole or should identify it before it gets to that point.

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