What type of valve has flow proportional to the position of the valve stem?

The type of valve that has flow proportional to the position of the valve stem is known as a linear valve. These valves are specifically designed to provide a flow rate that changes in a linear relationship with the position of the valve stem. This means that as the valve opens or closes, the flow rate adjusts proportionally to the stem's position within its range of motion.

Linear valves are commonly used in applications where precise flow control is required, such as in HVAC systems or chemical processing. The ability to have a predictable flow response based on stem position allows for better control of processes that depend on accurate flow rates.

In contrast, on/off valves operate fully open or closed, thereby not providing proportional control. Check valves allow flow in only one direction and do not adjust flow based on valve stem position. Solenoid valves are typically used for on/off control in automation systems and also do not provide a proportional flow response.