Surface Safety Valve 2 : A device mounted in the wellhead assembly that serves to stop the flow of fluids from the well should damage occur downstream of the well. (WLOP)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}