What are the two positions of a gate valve?

A gate valve is designed to act as a switch for fluid flow, allowing it to be either fully open or fully closed. In the fully open position, the gate valve allows maximum flow with minimal resistance, effectively facilitating the fluid passage. When the valve is fully closed, it creates a complete seal to prevent any fluid from passing through, ensuring isolation of sections of a piping system whenever necessary.

The primary function of gate valves is not to regulate flow but to provide a reliable shut-off capability. Therefore, their operational design emphasizes these two positions: fully open for unrestricted flow and fully closed for complete blockage. This is why the correct answer focuses solely on these two definitive positions, capturing the essence of the gate valve's utility.

The other options present scenarios that imply a degree of flow regulation (half open or partially open), which is not the intended use of a gate valve. Such positions may be relevant in other valve types like globe valves or ball valves, which are designed to manage flow rates. However, for gate valves, the clear and distinct states of fully open and fully closed are the defining characteristics of their function.