To test some vessel for vacuum you don't need vacuum at all.

Vessel have to sustain pressure difference between inside and outside. When vessel in vacuum, you have pressure difference of 1 bar. 1 bar absolute inside, 0 bar absolute outside.

To properly test vessel for that pressure difference you just pressurise it to 2 bar absolute inside. With 1 bar of normal atmospheric absolute pressure outside you have exactly same pressure difference as if vessel with 1 bar in vacuum.

To be shure that vessel is OK and will not leak, pressurise it to 3 bar of internal pressure. If it is perfectly sustain 2 bar pressure difference, then it will certainly sustain 1 bar pressure difference. You could even fill it with easy detectable gas to locate the leaks if any. Much more practical than using vacuum chamber for the same.

Vacuum chamber is necessary to test other things - behaviour of lubricants in outside moving parts, coatings, and other things that have nothing to do with vessel strength. And you don't need to put whole vessel into chamber for that tests.

Vacuum is not "destroying everything horrible sucking out hell". It is just 1 bar pressure difference, nothing more, very tiny difference. You have 2 bar pressure difference in your tires, 5-6 bar in your LPG tank, 3-4 bar in plumbing and 15 bar in your coffee machine. We interfere with larger pressure differences every day and barely noticing it.

Comparison of 10^-6 torr with 10^-12 torr when your vessel internal pressure is 1 bar or 750 torr is senseless. Both are negligeable and close to zero. In the terms of forces applied to vessel with atmospheric pressure inside in vacuum this "huge" difference of 10^6 between 10^-6 and 10^-12 is just 0.0000013%. Yea, I know, math and engineering is racist white supremacy horror.

To test some vessel for vacuum you don't need vacuum at all.

Vessel have to sustain pressure difference between inside and outside. When vessel in vacuum, you have pressure difference of 1 bar. 1 bar absolute inside, 0 bar absolute outside.

To properly test vessel for that pressure difference you just pressurise it to 2 bar absolute inside. With 1 bar of normal atmospheric absolute pressure outside you have exactly same pressure difference as if vessel with 1 bar in vacuum.

To be shure that vessel is OK and will not leak, pressurise it to 3 bar of internal pressure. If it is perfectly sustain 2 bar pressure difference, then it will certainly sustain 1 bar pressure difference. You could even fill it with easy detectable gas to locate the leaks if any. Much more practical than using vacuum chamber for the same.

Vacuum chamber is necessary to test other things - behaviour of lubricants in outside moving parts, coatings, and other things that have nothing to do with vessel strength. And you don't need to put whole vessel into chamber for that tests.

Vacuum is not "destroying everything horrible sucking out hell". It is just 1 bar pressure difference, nothing more, very tiny difference. You have 2 bar pressure difference in your tires, 5-6 bar in your LPG tank, 3-4 bar in plumbing and 15 bar in your coffee machine. We interfere with larger pressure differences every day and barely noticing it.

Comparison of 10^-6 torr with 10^-12 torr when your vessel internal pressure is 1 bar or 750 torr is senseless. Both are negligeable and close to zero. In the terms of forces applied to vessel with atmospheric pressure inside in vacuum this "huge" difference of 10^-6 torr is just 0.0000013%.

To test some vessel for vacuum you don't need vacuum at all.

Vessel have to sustain pressure difference between inside and outside. When vessel in vacuum, you have pressure difference of 1 bar. 1 bar absolute inside, 0 bar absolute outside.

To properly test vessel for that pressure difference you just pressurise it to 2 bar absolute inside. With 1 bar of normal atmospheric absolute pressure outside you have exactly same pressure difference as if vessel with 1 bar in vacuum.

To be shure that vessel is OK and will not leak, pressurise it to 3 bar of internal pressure. If it is perfectly sustain 2 bar pressure difference, then it will certainly sustain 1 bar pressure difference. You could even fill it with easy detectable gas to locate the leaks if any. Much more practical than using vacuum chamber for the same.

Vacuum chamber is necessary to test other things - behaviour of lubricants in outside moving parts, coatings, and other things that have nothing to do with vessel strength. And you don't need to put whole vessel into chamber for that tests.

Vacuum is not "destroying everything horrible sucking out hell". It is just 1 bar pressure difference, nothing more, very tiny difference. You have 2 bar pressure difference in your tires, 5-6 bar in your LPG tank, 3-4 bar in plumbing and 15 bar in your coffee machine. We interfere with larger pressure differences every day and barely noticing it.