So what happens inside the cylinder once the perfect vacuum is reached assuming the piston seals hold? I understand that the load continues to drop as the vacuum is not enough to hold the load. It's almost like we create a perfect vacuum but then the piston continues to "increase the perfect vacuum". What is actually happening in this scenario?
Atmospheric pressure is only 14.5psi. So not much compared to hydraulic pressures.
Exactly what you say, but hard to get a mental "handle" on. Bottom line, it takes zero extra force to expand a perfect vacuum. If you can get ahold of a syringe you can prove it to yourself.