Definition(s)
Emergency Shutdown Valves. (ESD)
Typically remotely actuated valves, preferably gate, butterfly or plug, mounted to outlet on flow cross. Valve is functioned in cases of unplanned release of well returns due to breach in flow back system. Actuated by air, hydraulics, or electrical signal over hydraulics.
Source: IADC UBO / MPD Glossary, December 2011. Global Standards