How are sealed gas cylinders (like in office chairs) filled/pressured?

Question

Like, they don’t have an opening right? How are they sealed?

EDIT: I should rephrase: there has to be some sort of machine that pressurizes, and, in the pressurized environment, seals the opening while not letting out air. How does that look like?

In: Engineering

Answer 1

As others have said, they happen to have sealable openings or valves buuuut…

Lets say you needed a sealed vessel that has no openings after its manufacture. You would achieve this by constructing the cylinder/vessel in either a vacuum or compressed chamber.

So if you want a pressurized component you would construct your part under pressure so when you remove it, the space inside your now sealed part would contain the same pressure as the “room” it was built in.