Every valve needs a means by which it can be operated (i.e., cycled or actuated). There are a variety of options to achieve this, including handwheels, levers, gears, and actuators.
Manual operators, such as gears require little peripheral planning beyond the installation and orientation of operators in the process line. Gears are simple machines that use a series of mechanical parts to increase efficiency—the mechanical advantage that the user gains.
Opening or closing valves can be completed either by manual input or automated devices driven by various energy sources. Manual operators are simple and inexpensive and require little peripheral planning beyond the installation and orientation of operators in the process line. Automated devices, on the other hand, require input energy systems, control systems, additional installation space, and infrastructure for support, operation, and maintenance.
Two concerns considered during the selection of manual operators are the effort required to operate the valve and the number of turns they require. A lot of effort and a high number of turns can result in personnel fatigue, safety concerns, excessive time for operation, and the need for multiple personnel. Another factor influencing the selection of manual operators is the valve’s expected frequency of operation and the physical location of the operation (that is, high in a superstructure or situated in an inhospitable environment), which could also present challenges to personnel.
Designers must weigh all of these factors in their decision matrix to receive the most productive yet acceptable selection of how a valve should be operated. Two aspects that primarily define operator selection are human factors and economic factors. Human factors can be defined as the human capability to cycle the valve in a safe, timely, and economically sound manner. These factors require considerations such as the work needed to be done (turns and rim pull, which is the amount of force put on a handwheel) to operate the valve, the environment in which the valve is located, the time required to complete the task, and the health and safety of the personnel involved. Economic factors include the cost of the actuator as well as the cost of infrastructure, which could include wiring, control systems, power, and ongoing maintenance to support automated solutions.