Great description, Carl.
Originally Posted by skiman
I believe the tank has an air bladder in it.
Some pressure tanks don't have a diaphragm or bladder - just pressurized air in the top of the tank. In this case, the Amazon description says it does have a diaphragm... presumably clamped between the moulded tank halves to separate the air in the end with the air valve and the water in the end with the plumbing fittings.
One of the distributors of this accumulator offers a datasheet
which provides a good description of how it works and how to use it.