The way in which valves are operated, meaning how they are opened and closed, is an important system design factor. Types of valve operation include:
- Manual handwheel: One or more crew members on-site turn a handwheel to crank the valve open or closed.
- Manual piston-assist: A crew member on-site activates a switch which results in a piston opening or closing the valve. The piston operates using gas pressure from the pipe.
- Automatic local control: A local control system senses when conditions are outside of safe tolerances and activates a switch which results in a piston closing the valve if operating.
- Remote control: Personnel in central location operate the valve remotely by sending a signal via SCADA (Supervisory Control and Data Acquisition) which activates a switch resulting in a piston opening or closing the valve
The type of operation determines the amount of time required to open or close a valve. This can be important during emergency situations or rapidly changing system conditions. Manually operated valves must include crew travel time in a calculation of the time required to operate the valve.
Speed of operation comes with a significant cost. Installation of automatic or remote-controlled valves can cost as much as one million dollars each, so they are only used at critical locations.
The table below shows the pros and cons of each operation type: