How do those huge gas storage things that go up and down, work?

Answer 1

it is like a big drinking glass upside down with the bottom in water
the gas inside pushes up on the inside of the top. ain other words it floats on top of the gas. the water around the edges seal the bottom
as the gas is used inside it drops and as it fills it goes up the weight of the tank maintains the same pressure all the time.

Answer 2

I believe you are referring to the oil pumping units ( nodding donkeys) for lifting crude oil out of the earth. The arm is weighted on one end and the same end is attached to a sucker rod. It works much in the same way a hypodermic syringe. Almost always driven by electric motors, the rod uses motor power to lift the sucker rod filling it with the crude oil. Once at full stoke the weighted end takes over, dropping the rod wlich causes it to pump the crude out. The cycle begins all over.

Answer 3

You mean pumping units? It works with an engine and gravity.