Constant volume pressure compensator

A method for equalizing pressure between an interior of an underwater system and the surrounding underwater environment, said method comprising the steps of:

• A) providing a pneumatic reservoir containing a high pressure compressible fluid;
• B) connecting a pressure compensating valve (PCV) in fluid communication with said vessel interior and said environment;
• said PCV comprising a valve body having a interior orifice, a pneumatic inlet orifice, a backflow orifice and an environment orifice, and a valve plug having a substantially uniform cylindrical surface slidably positioned within said valve body with no substantial gap between the valve body and the cylindrical surface, said valve plug being formed with a longitudinal conduit and at least one transverse duct in fluid communication with said conduit;
• C) establishing a path of fluid communication from said reservoir through said valve plug and into said interior while said valve plug isolates a fluid path from said environment to said interior;
• and,
• D) establishing a path of fluid communication from the surrounding underwater environment through said valve plug and into said interior while said valve plug isolates said underwater environment from said reservoir.