Emergency Shutdown System, in short ESD, is the most important set of equipment used during oilfield operations, such as drilling, completion, frac work, well test and production. ESD system usually consist of Emergency Shutdown Safety Valve, ESD Control Panel, piping and pushbutton. Emergency Shutdown Safety Valve, also known as Surface Safety Valve (SSV), is a shutdown gate valve with hydraulic or pneumatic actuator, which activates when emergency occurs. 

This flow diagram shows the signals from several well test equipment, which may trigger the ESD to shutdown the line by means of Surface Safety Valves in Flowhead (STT) and Line Surface Safety Valve serving as standalone safety equipment.

Also, picture shows that operating personnel may shut-down the line by pushing push-buttons in case of emergency. Push-buttons usually are installed on the ESD panel. However, if the client wishes to equip additional push-button on the process equipment, such as test separator and laboratory cabin, vendor can provide customized design and fabrication of ESD system.