On an oil drilling rig, the blow-out preventer (BOP) is a valve system at the wellhead that can be activated quickly to close the space around the drill, or even completely close an open drill hole.
There are multiple BOP valves used on each rig, and the valves are controlled hydraulically.
When excessive pressure in the hole causes a "kick", the BOP is used to prevent a blow-out.
Hoses that connect the BOP to the hydraulic system are required to have thick, flame resistant covers that allow them to survive in the case of a fire, so that the BOP still functions.