Review Flashcards
The earliest control valves used in the industry are:
Manual Globe Valves
In liquids, choking occurs as a result of vaporization of the liquid when the static pressure within the valve drops below the vapor pressure of the liquid.
True
Which one of the following Flow Meter is used to measure mass flow directly?
Coriolis Flow Meter
Which one of the following control valve characteristic is recommended if the control valve pressure drop is constant?
Linear
Which one of the following flow meters is limited primarily to water and waste water applications?
Magnetic Flow Meters
Another common name for Beta ratio (b) is ______________.
diameter ratio
Which one of the following Equation Constant be used, if sizing the control valve for a liquid flow rate in mass units (lb/h or kg/h).
N6
The coefficient of discharge (Cd) is the ratio ___________________________ .
of the true flow to the theoretical flow based on Bernoulli’s theorm.
The control valve size must:
be smaller or same size as the pipe size
Which one of the following control valve characteristic is recommended if the control valve pressure drop is increasing DP with increasing load, DP at Maximum load >200% of Minimum load DP?
Quick Opening
Valve Sizing Coefficient
Cv
Equation constant, if sizing the valve for a flow rate in volumetric units (gpm or m3/h)
N1
Compressibility factor
Z
Expansion factor
Y
Molecular weight
M
Mass rate of flow
w
Volume rate of flow
q or Q
Liquid specific gravity
Gf
Piping geometry factor
FP
Numerical constant
N
Differential pressure flow meters rely on a(n) ______________ in the pipe to cause a differntial pressure between the upstream and down stream.
obstruction
Which one of the followinf flow metes are simple,inexpensive and works well with clean liquds and gasses?
orifice plate
When cavitation occurs, it is located:
downstream of the vena contracta
Which one of the following devices does not collect information about the process variable and its relationship to desired setpoint?
control valve
Given that the inside diameter of a pipe is 6.065 inch, then the nominal pipe size is:
6 inch
Which of the following statements about control valves is True?
cavitation is more harmful to the valve than flashing
When a fluid passes through a control valve, the pressure is lowest:
where the velocity of fluid is highest
“Chocked Flow” in a control valve occurs when:
the flow through a valve is at its maximum
The Reynold Number Factor (FR) for flow through a control valve is calculated to be 0.7. Hence the flow can be charcterized as:
Transitional Flow
If the specific volume of water at a given temperature is known, then the density of water at that temperature:
can be obtained by taking the inverse of the specific volume value
For stream flow, the transmitted impulse lines should come off:
the side of the line
following pressure profile before and after a control valve in a pipe:
P1 600kPa
P2 250 kPa
Pv 300 kPa Pv is vapor pressure of liquid
Pvc 200 kPa Pvc is pressure at venacontracta
These values indicate that the control valve will experience:
Flashing
Which of the following is a valid trim for control valves in the Fisher specification Mangaer software
equal percentage
The sound pressure level that is two times more powerful that 50dB is
53 dB
A valve currently exhibits cavitation. which of the following does not reduce cavitation?
increase the temperature of the process fluid
A valve with flow change with large stem movement at full stem travel best describe a(n) ___________ valve
quick opening
Which one of the following control valve characteristic is recommended if the control valve pressure drop is decreasing DP with increasing load, DP at maximum load
Equal Percentage
Differential pressure flow meters rely on a(n) ______________ in the pipe to cause a differntial pressure between the upstream and down stream.
obstruction
For fluid such as crude petrolium and its liquid products, with vapor pressure _____________ atmospheric pressure at base temperature.
less than or equal to
Which one of the following control valve characteristic should be considered where highly varying pressure drop conditions can be expected.
equal percentage
Which one of the following control valve characteristic is recommended if the control valve pressure drop is constant?
Linear
Which one of the following control valve characteristic is recommended if the control valve pressure drop is increasing DP with increasing load, DP at Maximum load >200% of Minimum load DP?
Quick Opening
The Reynolds Number is a function of ____________
flow rate
The common rule of thumb used in sizing a modern control valve is
Make the size of the control valve one size smaller than the line size
Valves with a(n)__________flow characteristic used on pressure control applications
equal percentage
The Bernoulli coefficients are used only when the inlet piping diameter to a valve is equal to the outlet piping diameter
False
The calculated deltaPmax value is compared with the actual pressure drop specified in the service conditions, and the greater of these two values is used in the sizing equations
False
If the flow rate is m^3/hr and the pressures are pa, then N1 becomes 0.0865
true
The most commonly used fitting in control valve installations is the short length concentric reducer
true
Which one of the following Equation constant be used, if sizing the control valve for a gas flow rate in volumetric units and only if the specific gravity is known
N7
The rate of flow through a valve under stated conditions
Valve Capacity
It is the ratio of the magnitude of the output change of a given system or device to the magnitude of the input change that cause the output change
Gain
The range through which an input signal be varied, upon reversal of direction, without initiating an observable change in the output signal
Dead Band
A servomechanism that is mechanically connected to a moving part of a final control element or its actuator and that automatically adjusts its output to the actuator to maintain a desired position in proportion to the input signal
Positioner
A valve trim element used to modulate the flow rate with either linear or rotary motion
Disk
the internal components of a valve that modulate the flow of the controlled fluid
Trim
The maximum difference in output value for any single input value during a calibration cycle, excluding errors due to dead band
Hysteresis
A pneumatic, hydraulic or electrically powered device that supplies force and motion to open close a valve
Actuator
The minimum possible change in input required to produce a detectable change in the output when no reversal of the input take place
Resolution
The interconnection of process control components such that the information regarding the process variable is continuously fed back to the controller set point to provide continuous, automatic corrections to the process variable
Closed Loop
A movable pressure responsive element that transmits force to the piston actuator stem
Piston
The portion of the valve that contains the packing box and stem seal and can guide the stem
Bonnet
The portion of the rotary shaft control valve assembly corresponding to the valve stem of a globe valve
shaft
The part that connects the actuator to the valve stem and transmits motion (force) from the actuator to the valve
Actuator Stem
The symmetrical flow controlling member used in the most common varieties of butterfly valves
disk, conventional
A part of a valve trim that surrounds the closure member and can provide flow characterization and/or a seating surface.
cage
A flexible, pressure responsive element that transmits force to the diaphragm plate and actuator stem.
Diaphragm
The portion of a rotary-shaft control valve assembly corresponding to the seat of a globe valve
Seal ring
A valve design in which one port is collinear with the valve stem or actuator, and other port is at right angle to the valve stem
Angle valve
The most common type of segmented ball control valve
Ball, V-notch
