Master valve

{
  "id": "MLC-T-OAG-004378",
  "term": "Master valve",
  "field": "Oil and gas",
  "definition": "A large, high-pressure valve located on the Christmas tree that controls all flow from the well. It is the primary barrier between the reservoir pressure in the tubing and the external environment, and it is normally kept fully open during production. There are two master valves on a typical tree: a lower one that is manually operated and an upper one that is hydraulically or pneumatically actuated for remote or emergency shutdown.",
  "subject": "Well Completions",
  "url": "https://mlchart.com/terminology/oil-and-gas/master-valve/"
}