Sorry to disagree, but none of the above as far as what the hydro does test. Those above (pressure variations, including transients) can be determined and can be protected against by analysis and setting MAOP according to the code limitations.
The reasons I would say for hydrotest are to prove Integrity & close immediate leaks and would include,
Failure Pressure Versus Defect Size
Manufacturing Defects
Pipe manufacturing codes (for example API 5L [9]) give limits of acceptable defects, which set the standard for detection; many mills use internal standards that meet the criteria given in codes but can still miss some defects. Hydrotest ensures that remaining defects are small enough to still allow operation within MAOP. The hydrotest is designed to induce a stress that would cause failure of under-matched or substandard pipe properties (e.g. wall thinning, tensile properties below SMYS, or defects).
Transit by road, rail or boat
May damage the pipe or subject the linepipe to cyclic stresses that can result in fatigue cracks.
Deficient Workmanship
Since pipeline integrity is much more likely to be affected by longitudinally oriented defects than by circumferentially oriented defects, hydrostatic testing is one of the best ways to demonstrate the integrity of a pipeline.
To expose those and any other remaining defects that have survived previous test and inspection processes.
Hydrotest is considered the final test of pipeline integrity.
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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that
99% for pipeline companies)
