Abstract: A tool which employs an internal fluid during operation in a subterranean environment at elevated pressures and/or temperatures, the tool including a modular pressure compensator component which can be easily and rapidly replaced as needed. Also described is a related method of maintaining a tool which employs an internal fluid during operation in a subterranean environment at one or more pressures above atmospheric pressure, and a related method of compensating for pressure changes within a tool which employs an internal fluid during operation in a subterranean environment at super-atmospheric pressures.