SSIV 1 : Sub surface (or subsea) isolation valve. Often placed in offshore pipelines within a few hundred meters of the facility to give an emergency stop point in the event of a line rupture or fire
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}