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Comment by WalterBright | Hacker News Reader

You can't eliminate pipe leaks, etc. But you can compartmentalize to minimize the damage a leak does, much like dividing a ship into watertight compartments.

The hydraulic system on a Boeing jetliner is compartmentalized so that a leak in one of the systems doesn't drain away all the hydraulic fluid in that system - only the actuators downstream of the leak get affected.

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On the contrary, you can eliminate pipe leaks easily - just many areas have fairly lax integrity management requirements for operators, and those that don't only apply to new lines - very rarely does legislation cover preexisting pipelines.

New pipelines (especially ones considered DOT regulated in the US, overseen by PHMSA) typically are installed with automatic block valves and flow level leak detection systems. Those combined with a sensible internal and external corrosion control program can push the life of a pipeline without incident out past the useful life of the pipeline. But retrofitting these is expensive and most pipeline operators won't do it without regulatory or other political pressure.

> you can eliminate pipe leaks easily

Famous last words. A better design is to assume leaks occur, and design to minimize the damage. (This is how airliners are designed.)

> with automatic block valves

That's compartmentalization, not elimination.

Another method is to use two smaller pipes instead of one larger one - it reduces the scale of any leak.

  use two smaller pipes instead of one larger one - it reduces the scale of any leak.

... while doubling the exposure to failure in the first place.

This actually ends up increasing your likelihood of failure, as smaller parallel lines mean higher operational costs for smart pigs and other integrity assessment tools making internal issues harder to detect before failure, and increased risk for external failure due to cathodic protection system failures due to interference and shielding.

Of course it doubles the risk of failure, but each failure does half the damage.

Which sounds like a terrible trade-off, harm isn't linear here. Two leaks, each of 1000 barrels, will badly damage two different valleys. One leak of 2000 barrels would be better.

And cost isn't linear either, two half-capacity pipes will probably be almost twice the price. You could spend that on more steel for the large pipe instead.

Actually, I'm not so sure about doubling the risk. Failures may appear random, but they aren't. A failure may indicate a particular defect that can be corrected in the rest of the system before another one fails.

Er... I don't think you've completely taken into account what you're proposing. Due to the square-cube law, splitting a pipeline into two smaller pipelines means that in order to have the same total cross-sectional area you would need sqrt(2) times as much surface area. Not only is the surface area that is subject to corrosion increased, I would imagine the pipe wall thickness would probably decrease so corrosion would compromise the integrity of the pipeline even sooner. It's also double the number of welds that need to be made, double the length of pipeline to maintain, and as to the notion that it would do half as much damage, I doubt this claim. Why would it actually substantially decrease the damage to the environment? It's not like pipeline leaks completely sever the pipeline in half and just start inundating the surrounding area with a flood of oil. It's usually a crack or pinhole leak, so the smaller cross-sectional area of the pipe probably won't do much good in terms of decreasing the volume of oil leaking out.

With proper monitoring and a well maintained internal corrosion control and external threat control systems you can stretch out the timeline for non "acts of god" (ie natural disasters, terrorist attacks, etc) to greater than the life of the structure. The methods for internal and external control are well understood and practiced to varying degrees of effectiveness.

Elimination of the hazards is impractical, so minimization of risk exposure and frequency is the best that can practically be done.

All the hubbub about stopping new pipeline construction means that more incident prone methods are used - be it trucking, rail transportation, or use of 50+ year old pipelines. The new lines are better engineered, understood, and have more stringent operational controls in place. I've worked on pipelines from the 1940's that are still safely operated, and lines from the 2010's that have already self excavated. These things can be controlled with the right engineering, organizational, and governmental oversight.

Compartmentalizing risk as acts of god is a rather pointless exercise. If you can’t eliminate risk you need to be intellectually honest and say why that risk is acceptable. The Midwest for example gets large earthquakes in seemingly random locations, that’s a known issue and needs to be accounted for in a risk assessment.

As to other transport methods being less safe that also comes down to building safe systems. Car gas tanks for example are designed to survive crashes without spilling their contents. You can also build tanker trucks/trains to appropriate standards.

It seems you're not familiar with the history of US pipelines. It doesn't matter what theoretical technologies or regulations exist, because oil extraction industries get away with leaking hundreds of thousands of gallons of oil with little or no punishment or recompense, including on the farmlands they steal from people to run their pipelines across.

See the thousands of dots? Each is a spill.

https://projects.propublica.org/pipelines/

https://www.theguardian.com/us-news/2017/may/10/dakota-acces...

https://theintercept.com/2018/01/09/dakota-access-pipeline-l...

https://www.cnn.com/2017/11/16/us/keystone-pipeline-leak/ind...

https://en.wikipedia.org/wiki/List_of_pipeline_accidents_in_...

Out of curiosity, did you intentionally choose examples reminiscent of the Titanic and 737MAX?

First off, my first real job was designing the flight critical stab trim system for the 757. I have an enduring interest in airplane flight control systems, and follow airliner crashes and the resulting fixes. The hydraulic changes preventing leak propagation resulted from the Sioux City crash where the compressor disk in the tail engine came off and sawed through each of the triply redundant hydraulic lines, resulting in total loss of the hydraulics. The 737MAX troubles have nothing to with the hydraulic system.

The Titanic disaster did popularize the notion of watertight compartments, but these are well known and used in warships. Warships are very hard to sink because of it. The Bismarck is suspected to have sunk only because the captain flooded it to prevent its capture.

Submarines use compartmentalization to minimize flooding risk, and surely the space station must, too.

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