Which of the following facilitates close control of flow of fluids ?

ANS:B - Globe valve

Among the options provided, the globe valve facilitates close control of the flow of fluids. Here’s why:

• Globe Valve: Globe valves are designed to provide precise control over fluid flow. They have a linear motion disk (or plug) that can be moved against the flow to vary the flow rate through the valve. By adjusting the position of the disk, the flow can be finely regulated from fully closed to fully open, allowing for accurate control of the flow rate.
• Gate Valve: Gate valves are primarily used for fully open or fully closed positions and are not typically suitable for fine flow control due to their design that creates turbulence when partially opened.
• Butterfly Valve: Butterfly valves are used for quick operation to fully open or fully close, rather than for precise flow control. They are often used in applications where rapid shut-off or isolation is needed.
• Check Valve: Check valves are designed to allow flow in only one direction and do not provide control over the rate of flow.

Therefore, when close control of fluid flow is required, a globe valve is the most suitable choice among the options given. A globe valve is a type of linear motion valve that is widely used to regulate the flow of fluids in pipelines. It derives its name from the shape of its body, which resembles a globe or sphere. Here are the key components and characteristics of a globe valve:

1. Body and Construction:
   • The body of a globe valve is generally spherical or cylindrical in shape.
   • It has an inlet and an outlet, typically aligned in a straight line, which makes it suitable for applications where a straight flow path is needed.
2. Valve Disc and Seat:
   • Inside the valve body, there is a movable disc or plug that can be raised or lowered onto a seat to regulate the flow of fluid.
   • The disc is connected to a stem that extends outside the valve body, allowing it to be operated manually or by an actuator.
3. Flow Control Mechanism:
   • Globe valves control flow by the linear motion of the disc perpendicular to the flow path.
   • When the valve is fully open, the disc is lifted completely off the seat, allowing maximum flow.
   • By gradually lowering the disc onto the seat, the flow area is reduced, thereby controlling the rate of fluid flow.
4. Types of Globe Valves:
   • Angle Globe Valve: This variation has the inlet and outlet at an angle, which can be advantageous for applications where space is limited or where flow direction needs to be changed.
   • Straight Globe Valve: This type has a straight flow path through the valve body.
5. Applications:
   • Globe valves are suitable for applications requiring fine flow control, such as throttling and regulating flow.
   • They are commonly used in industries such as water treatment, HVAC (heating, ventilation, and air conditioning), power generation, chemical processing, and petrochemicals.
6. Advantages:
   • Precise flow control: Globe valves offer excellent control over the flow rate due to the linear motion of the disc.
   • Good shutoff capability: When fully closed, globe valves provide a tight seal against fluid flow.
   • Versatility: They can handle a wide range of temperatures and pressures depending on the material of construction.
7. Disadvantages:
   • Pressure drop: The design of globe valves can cause significant pressure drop across the valve, particularly in fully open or partially closed positions.
   • Maintenance: Due to their internal construction and moving parts, globe valves may require more frequent maintenance compared to other types of valves.

In summary, a globe valve is a versatile and widely used valve for controlling the flow of fluids in various industries, offering precise regulation and good shutoff capabilities where needed. Its design makes it particularly suitable for applications requiring accurate flow control rather than simple on-off operation.