Which of the following is not a part of a flow control valve?

A flow control valve is designed to regulate the flow of air or fluid in a pneumatic system. The components of a flow control valve typically include a body, an adjustment screw, and in some designs, a check valve.

The body serves as the main structure that houses all the other components and facilitates the flow through the valve. The adjustment screw allows for precise control over the flow rate by altering the size of the opening through which the fluid or air passes. A check valve may also be included in certain flow control designs to prevent backflow, ensuring that the fluid flows only in one direction.

In contrast, a vane is not a standard part of a flow control valve. Vanes are more commonly associated with rotary mechanisms or certain types of pressure control devices where they can serve different purposes such as directing the flow or acting as a part of a motor. Therefore, identifying the absence of the vane as part of a flow control valve makes it the correct answer to the question.