QUIZ 2

Following are incorrect about the control valve except:

• The valve is malfunction without an actuator

• control process conditions

• Compare the 'setpoint' value to a 'process variable'

• Adjust the flow rate of fluids in pipeline

Following are range of signals accepted for the control valve except:

• 0.2-1.0 bar

• 4-20 psi

• 4-20 mA

• 3-15 psi

Following are the functions of actuator except:

• Adjust the position of the valve stem

• Adjust the position of the valve body

• Moves the valve to a fully-open or fully-closed position

• Accepts a signal from the control system

Following are TRUE about butterfly valve except:

• Used for corrosive liquids at low temperature

• A linear motion valve

• Stem is used to connect the actuator with the disc valve

• Used for throttling and on/off service

Following are TRUE about globe valve except:

• Flow can be regulated by the percentage of the opening of the valve

• Good shutoff capability

• Consists of spherical ball located between two sealing rings

• A linear motion valve

The different types of control valves are classified by a relationship between the valve stem position and _______ ?

Following conditions exist when the valve outlet pressure is less than the fluid vapor pressure. The fluid enters the valve as a liquid and exits as a vapor

• Flashing

• Nominal

• Inherent

• Cavitation

Following flow characteristics commonly used for control application. The imitations of this characteristics is the flow does not shut off completely

• Equal percentage

• Quick opening

• Linear opening

• Fast opening

Which one is the cause for cavitation damage and subsequent performance degradation

• The violent collapse of the vapor bubbles near the valve component surfaces

• The static pressure of the flowing liquid decreases to a value less than the fluid vapor pressure

• The pressure recovered back to a value above the fluid vapor pressure

'A valve a linear flow characteristic produces flow directly proportional to the valve lift'.

The above statement is best describe:

• Percentage opening

• Quick opening

• Linear opening

• Fast opening