While I certainly buy the argument that a nozzle that is excessively overloaded may cause the failure, I can't say I'm convinced in this case.

I've reviewed a number of existing systems for clients who, after putting up with years of high maintenance issues, realized that the piping configuration could be the issue. It is a a surprisingly major leap for most people not involved in stress analysis to think that a piping configuration can have anything to do with the reliability of rotating equipment. But's that another topic altogether

Now, there are three reasons I doubt that the piping system is the cause here:

1. Some of the systems I've reviewed have turned out to be 500% and more over published allowables during operation. Even under these loads, the machines don't fail instantaneously, but they do have to come down every 3-6 months for major work.

2. If the first support was so heavily loaded as to create a friction anchor in front of the pump, I can't see how they ever would have gotten it bolted up in the first place. The reason is that, unless the support were to be able to act directly under the cg of the pipe span, that much vertical load would impose a substantial moment on the connection at bolt up and I can't see the shaft passing the alignment check with the kind of load we would have to be talking about.

3. In order to have friction, something has to try to move. In the case of the systems we look at, that movement comes from thermal expansion, which is not an instantaneous process. As the lines comes up in temperature, it is slowly going to try to expand. The static friction load is going to build from zero, over time, up to the maximum that the normal force can sustain. I find it hard to believe that you would have a combination of such high normal force and quick expansion to produce a reaction capable of causeing such a catastrophic failure in a matter of seconds.

Of course, these are just the ramblings of one analyst. I know the question was specifically about friction and that, supposedly, the vendor had eliminated other possible failure sources. However, what is stated and what is true aren't always the same thing.

Now, my observations are based on my own experience, which is by no means exhaustive. I would certainly appreciate responses from the group of experiences where a piping system was so poorly layed out as to cause a instantaneous catastrophic failure of a rotating piece of equipement. I'd also be curious to know how it passed the shaft alignment check.