Top 25 MCQs on Control Valve Types, Selection, and Applications for Project Engineers

Deadband is the lack of sensitivity in a valve’s reaction to tiny input signal variations.

Characterized balls change flow patterns to offer more consistent and linear flow properties.

Needle valves provide extremely precise flow control, making them an excellent choice for applications that require high precision and low flow characteristics.

Valves usually fail in specified locations (open, closed, or locked); mid-stroke is not a typical fail mode.

The effective control range of the valve is defined by the rangeability of the valve, which is defined as the ratio of the maximum controlled flow to the minimum controlled flow.

Especially with rapid processes, high gain causes overcorrection, weakening the control loop.

Balanced plugs lower the needed actuator force for movement by minimizing pressure drop across the plug.

Unlike cavitation, flashing results in permanent vapor phase following valve outlet owing to low downstream pressure.

This setup guarantees secure valve closure upon loss of air signal.

Oversized valves run in a tight range, which leads control loop instability and oscillations or hunting.

Positioners evaluate input data against stem position and modify actuator pressure to fit.

Soft seats, such as PTFE, guarantee bubble-tight shutdown, hence fulfilling zero-leakage criteria.

Rapid flow increase with little stem movement is made possible by fast opening valves, perfect for on-off use.

Control accuracy is impacted by valve authority, and a lack of authority results in a lack of controllability.

Diaphragm valves are perfect for slurry and corrosive media since they isolate internal parts.

Split range controls two valves over various signal segments using a single 4-20 mA signal.

The explanation is that Cv, which directs sizing, specifies the water flow rate through a valve at a pressure drop of 1 pounds.

Anti-cavitation trim works by gently dissipating pressure to stop vapor formation and lower noise.

Spring-to-open actuators move to the open position when air fails, hence guaranteeing fail-safe open conditions.

Cavitation is defined as the development of vapor bubbles that burst at pressure lower than vapor pressure, causing internal damage.

The value of the flow rate is directly proportional to the opening of the valve.
Explanation: In linear valves, every unit of stem movement causes the same change in flow rate.

Material compatibility with corrosive fluids guarantees safety and lifetime by preventing degradation.

Butterfly valves are affordable and appropriate for large-diameter applications with fair control precision.

Equal percentage valves provide more flow variation per unit of stem motion, perfect for different process needs..

Globe valves are ideal for throttling applications due to their precise flow control provided by their design.