Accumulator (pressure control device) : Canisters of hydraulic fluid, pressurized with a nitrogen gas cap of sufficient pressure and volume to operate all the rams on a BOP in case of power failure to the BOP
George E. King Engineering, 5000 Oilfield Terms: A Glossary of Petroleum Engineering Terms, Abbreviations and Acronyms, US 2010. http://gekengineering.com/Downloads/Free_Downloads /Glossary_of_Petroleum_Engineering_Terms_25_August _2010.pdf, (Oil - Amer) {593}