In gate valve, a gate slides between the seats of the valve. Movement of the gate is at right angle to the flow of fluid. By opening the valve, flow path is enlarged in a highly non-linear manner with respect to percentage of opening.
Gate valve is normally used for isolation application where only fully close or fully open position is required. this valve is suitable where frequent opening and closing is required. the gate fully retracts in the bonnet. so, the pressure drops across the gate is less.