TOPIC 5: MANIPULATOR ELEMENTS (MCQ – Level C2)

Which of the following is a function of a valve actuator?

• To measure flow rate

• To provide power to move valve components

• To increase the system voltage

• To cool the control valve

Pneumatic actuators are widely used because they are:

• Complex and expensive

• Slow in response

• Safe in explosive environments

• Operate only with hydraulic oil

Which type of actuator uses a flexible diaphragm to generate force?

• Hydraulic actuator

• Electric actuator

• Diaphragm actuator

• Rotary actuator

The “turn-down ratio” of a valve refers to:

• The ratio of minimum to maximum flow

• The maximum valve pressure

• The valve opening speed

• The size of the valve seat

If a flowmeter has a maximum flow of 200,000 m³/day and a minimum flow of 10,000 m³/day, the turn-down ratio is:

• 2:1

• 5:1

• 10:1

• 20:1

The main purpose of a positioner is to:

• Control the flow direction

• Ensure accurate valve stem position

• Increase the temperature

• Maintain constant pressure

A pneumatic positioner works by:

• Converting current to voltage

• Balancing air pressure and stem position

• Using oil pressure to move a piston

• Changing valve material composition

One advantage of using a positioner is:

• Increases hysteresis

• Reduces control accuracy

• Provides precise valve positioning

• Increases friction losses

Which condition indicates a positioner is needed?

• When valve operates in manual mode

• When accurate valve positioning and fast response are required

• When system pressure is constant

• When actuator is electric only

The butterfly valve is best suited for:

• Small line applications

• Large line, low pressure drop systems

• High-pressure isolation valves

• Precise laboratory control