Tony wrote:
"(Pipeline) Retesting is not done by pressure, as far as I know, but ny
dending "pigs" down the line to analyze the pipeline."

No surprise. Hydrostatic testing pressurized pipes to maximum pressure
or slightly more to prove their safety. This itself tends to aggravate
cracks.

A pig is a carriage (usually wheeless and propelled by differential
pressure) through the pipe. They serve many purposes. They can be used
for video inspections, ultrasonic tests, or X-ray review of a pipe.

When I was a pipeliner, they were often blown through a pipe to clear it
of trash and liquids.

Best regards, Richard Harrison, KB5WZI