Benefit of using a hydraulically actuated control valve
The main benefit of using a hydraulically actuated control valve is the use of line pressure as motive power to operate the valve.
Operating principal of the valve
- Sierra globe type control valves are closed-loop systems that utilizes line pressure as motive power to operate the valve. The main valve is controlled by a pilot that compares its spring setting (set-point) to the process variable for example (pressure, flow, and/or level), as the process variable changes, the pilot senses the change and compensates to keep the process variable as close to the desired set-point as possible. As such, these valves are single set-point control valves, and a set-point change will require operators to change the spring setting of the pilot.
- By changing pilot and pilot system on the main globe valves, it is possible to control pressure (upstream or downstream), flow or level (ground or elevated tanks), these valves operate without the need for external electric power it only utilizes the pressure power of liquid.