What are the two general classifications of valves?

The two general classifications of valves are based on their mode of operation, which are automatic and manual. Automatic valves are those that operate on their own, often in response to specific conditions or signals, such as pressure, flow, or temperature. These valves often incorporate sensors and actuators to open or close as required, without the need for human intervention, providing efficiency and safety in systems where continuous monitoring is essential.

Manual valves, on the other hand, require human operation to function. Operators use handles, levers, or wheels to open or close these valves as needed. Manual operation provides direct control and is often preferred in applications where human oversight is vital, or where system conditions may be too variable for automatic operation.

Understanding these classifications is essential for grasping how different valves operate within fluid systems in marine applications or other engineering contexts. The other options might cover specific types of valves or describe components of valve systems, but they do not broadly categorize valves in the same foundational way that automatic and manual do.