Two types of stabbing valves that must be prepared for well control are Full Opening Safety Valve (TIW valve) and Inside BOP valve (Gray Valve). We would like to describe what the differences between two valves are.
Full Opening Safety Valve or TIW valve
Full Opening Safety Valve or TIW valve is a ball valve designed for high pressure condition and it can hold pressure from both directions. It is called “Full Opening” because when the ball valve is opened; the flow path through the valve has a smooth inside diameter. One thing that you need to remember is that the term “Full Opening” does not mean that the ID of the valve is the same of drill pipe ID.
Figure 1 Full Opening Safety Valve