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leakage or explosion pressure

leakage or explosion pressure

leakage or explosion pressure

(OP)
steel pressure pipes : can you tell me, in case of failure, wich is the pressure for leakage and wich one for explosion ?
is there any difference between gas and liquid ?
This is just for my information (in fact I am working with potable water concrete pressure pipes) : I just need a flat answer (flat as much as possible)

Thanks

RE: leakage or explosion pressure

In general there is no such boundary. It is generally accepted that modern pipes operating at pressures below 30% of SMYS will only leak and not rupture. Above that 30% figure the same may apply, but as the stress level rises the possibility of a leak turning into a rupture rises. See attachment for an interesting paper.

Gas has a greater, though much lower nowadays, potential for a running ductile fracture which could literally unzip a pipeline. Look up running ductile fracture to see what I mean.

If you want to go much further you need to study fracture mechanics of pipes. Most of these assume some sort of weakness, a crack, gouge or loss of wall thickness due to corrosion.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

RE: leakage or explosion pressure

The other issue you get between gas and liquid is that if a leak occurs in a high pressure gas line, you can get very low temperatures which if the metal is not suited, can lead to brittle failure after a period of time. The other issue affecting rupture after leak is the size of the initial leak hole. A very small pinhole leak from corrosion will not normally transition to a rupture, but a long crack or gouge is more likely to develop if the steel stress is high.

This is for steel, I don't know about other materials in the same depth.

Hope it helps.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

RE: leakage or explosion pressure

Particularly prestressed concrete cyclinder pressure pipe withstands pressure (and for that matter competitive advantage/cost over other pipes) via a minimum weight per foot of a relatively small cross-sectional area of very high strength steel prestressing wires with also minimal actual safety factors particularly vs transient pressure events. Make no mistake about it, the "heart" of this pipe is this small steel wire, and the amount of steel in a pipe controls its overall cost or profitability more than other components. Very high strength can be both a blessing and a curse, as in materials in general there is often a trade-off in strength of materials and other desirable features. Among the trade-offs in very high strength steel wire reinforcements of concrete pressure pipe are loss of ductility (increased brittleness, or decreased overall toughness), and also susceptibility to various forms embrittlement due to manufacture and also the buried environment etc.(that can create additional flaws, that even if rather small can be problematic in very highly stressed and small cross-section fracture mechanics parlance). At the same time, the prestressing wires are also under inevitably quite high stress from both initial manufacture/prestress and eventual service at often meaningful trasnmission pressures. Some appreciation for influence of environment e.g. on eventual brittle failures of very high strength steel prestressing wires or tendons can be gained by reading the paper at http://oa.upm.es/9331/2/INVE_MEM_2010_86584.pdf and many others.
As to the explosive or self-excavating nature of some such brittle concrete pressure and other brittle pipe material failures, a reading of the document at http://www.wsscwater.com/file/EngAndConst/80footse... may be of interest to you, and particularly when it get into the discussion of 80 feet "set-back" and 200 feet "debris throw" figures etc. from pages 5-6 or so on.
Even ductile materials can experience brittle fracture under some circumstances as others have noted, but not generally in the modern age of the spectacular nature seen by brittle materials such as what you are dealing with, pvc, and gray cast iron etc.

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