Speaking of a vacuum back when i was in the navy a good friend of mine a Machinist Mate who worked down in one of the steam engine rooms once gave me a tour when we were out to sea and he was showing me all the different gages that they had to monitor once an hour and so one of them was a
vacuum gage which was always in the high 29 inGH range and he told me that a ''perfect'' vacuum inside the pipes was at 30 inHG and if that were to happen that the pipes would all implode. He stated that many times they read those gages at 30 inHG and so i asked why didn't the pipes implode and he told me that the gages were always slightly out of micro calibration.
Anyway just something i've never forgotten over the years
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