I think you are thinking of a different part than where I am. After I left the prison cells, through the tunnel you have to duck to go into,going down the hallway there is a big jump that requires perfect timing. But this part, I am stuck at, is right after you avoid two guards, you go into a big square room with the electric septor in the middle of the room. There is a extended arm that reaches out to you on the side of the room you enter.
There are three spiders on the left ledge, which has recharge gas dots to get you there. Ther is a scorpion on the right, which also has three recharge dots to get you to that ledge. Once you go to the middle of the room under the electricity source, you have to go to the ledge straight ahead of you. I tried the flamethrower, same result. Thank you.