Optimum control of the gas turbine requires that the actuator and valve accurately and quickly track the

demand signals transmitted by the control. The stop/ratio valve has been designed to provide output

forces that exceed the opening and closing requirements with some margin. The additional margin helps

ensure that the system moves rapidly even under service conditions where the valve has been

contaminated or worn. The hydraulic trip relay valve has been selected to provide high operating force

margins, high flow capacity, and to ensure the desired closure rate of the valve under trip conditions.

By using a long actuation rod between the hydraulic cylinder and the valve lever arm, the side-loading

forces on the actuator shaft and seals are greatly reduced, decreasing the wear between sliding parts,

and increasing the useful service life of the system. The ample distance between the wetted heavy-duty

linear slide rings within the stop/ratio valve accommodates any remaining side load. These provisions

provide extended service life even in severe service conditions.