what is the function of the bypass line with a ball valve followed by a globe valve?

[tobebest]

Hi, i am looking at the PID, and i don't know what is the function of the bypass line with ball valve and globe valve, can someone tell me? thank you in advance

 

[moltenmetal]

Can't open your attachment, but somebody doesn't trust that the globe valve will seal tightly when closed and wants the ball valve to be extra sure. That'd be my guess.

 

[SNORGY]

The globe valve is for poor man's flow control. After a while it won't seat, or so would be the fear. The ball valve is either fully open with flow controlled by the choke, or fully closed with the globe valve position irrelevant.