From a stress point of view, it might be easiest to think about the piece of pipe near the highest weld at surface, joining the pipe to the top hamper / christmas tree etc etc etc.
The top of the pipe is fixed at the ground level (say) at the end of construction.
Firstly, the pipe is being pulled vertically down by whatever weight of unsupported pipe hangs after drilling and insertion is finished.
Secondly. This force (net vertical down) is then offset by excess thermal expansion. - I suggest than there is no thermal expansion prior to fluid flow for all the 'gradual heating as inserted' comments from prior thread. - As fluid is run up the pipe it will expand, so 'vertical up' stress will depend on how much of the net temperature derived expansion is taken up by the fixing against the drill wall, hole floor and how much by compression against the fixed top.
Suggest some of the weight (net down force) will be offset. Say the pipe is supporting 800m up net weight. OK, that's a bit of weight.
These have all been vertical forces.
Thirdly, as the fluid comes up the pipe / the pressure at the top of the pipe will increase. Other posts have talked about very high psi (3000 or 5000psi? not sure if this is correct haven't been able to DMOR). This creates a hoop stress, horizontally, around the pipe.
Maybe offset by the pipe (again) being constrained by the rock / cement casing, which will reduce the stress. Imagine a balloon inside a glass bottle, once the bottle walls have been reached, the wall of the balloon ceases stressing (stretching) and just compresses.
I am not worried about compressing stress, is trivial (I suspect) in this case.
These stresses add up, in vectors, depending on how geeky you wish to be.
OK, the bit that worries me (why did it take THIS long u ask) is temperature.
As the temperature of steel (and everything else) goes up, its ability to not deform under stress goes down. It could be an interesting design challenge to calculate stresses based on knowledge of the conditions in the steel (as I sketched above) at ambient, and then ensuring the material has sufficient elastic capability to deal at elevated temperature.
If this is determined to be the cause, then the pressure bearing equipment will need to be re-specified.
High temp alloys are expensive. Esp if safety margins grow (once it has already gone bang).
NOT IMPOSSIBLE. Modern steam turbines (like in thermal power stations) have large steam mains at 5-7,000 psi and similar temperatures to these, do these are not new design challenges.
I suspect that it is just the last run of pipe that is failing under combined vertical and hoop stress, the above ground stuff should already be designed at temp & pressure - since it is not carrying any weight.
Just expensive, and if stuff needs to be rebuilt its more delays.
Oh, and besides.
If it is NOT this.
At least you can converse at parties where people talk about hoop-transverse strain vectors.
lol lol
f111 (Now, if you know yr history, this was a wing root stress failure, but not temperature related)
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