The blowout preventer is used to close the wellhead during oil testing, workover, completion and other operations to prevent blowout accidents. It combines the two functions of full seal and half seal. It has the characteristics of simple structure, easy operation, high pressure resistance, etc. , It is a safety seal wellhead device commonly used in oil fields to prevent blowouts. During oil drilling, it is installed on the wellhead casing head to control high-pressure oil, gas, and water blowout devices. When the oil and gas pressure in the well is high, the blowout preventer can close the wellhead (shut down). When the heavy mud is pressed into the drill pipe, there is a four-way under the ram, which can replace the mud invaded by gas, increase the pressure of the liquid column in the well, and suppress the ejection of high-pressure oil and gas.