Although liquids tend not to compress, gases do, so they can be used to load a volume of oil under pressure. In this type of accumulator, the gas (usually a relatively inert gas such as nitrogen) and hydraulic oil occupy the same chamber but are separated by a piston, diaphragm, or bladder. When circuit pressure rises, incoming oil to the chamber compresses the gas. When circuit pressure drops off, the gas in the chamber expands, forcing oil out into the circuit. Most gas-loaded accumulators are precharged with the compressed gas that enables their operation.
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