GASM 230 Test 3 Flashcards
(176 cards)
1
Q
- Name the sources of energy that are used to move the internal parts of an actuator. _
A
Pneumatic pressure, hydraulic pressure or electric current
2
Q
- This type of actuator has instrument air supplied to both sides of the piston and uses the air/liquid to both open and close the valve.
A
Double Acting
3
Q
- This type of actuator has instrument air supplied to only one side of the piston and uses a spring for energy on the opposite side.
A
Spring Return
4
Q
- This type of actuator has a “fail-safe” position.
A
Spring Return
5
Q
- This type of actuator is used in applications where the valve needs to fail in last position
A
Double Acting
6
Q
- Name the five types of actuator groupings
A
Pneumatic, hydraulic, direct gas, gas over oil and electric
7
Q
- These type of actuators use lower pressure compressed air or natural gas to generate the operating energy for the actuator.
A
pneumatic
8
Q
- These type of actuators use high pressure gas to generate the operating energy for the actuator.
A
direct gas
9
Q
- These type of actuators use an electric motor and some form of gear reduction to generate the operating energy for the actuator.
A
electric
10
Q
- This type of actuator is typically used with valves requiring shorter travel such as globe valves
A
diaphragm
11
Q
- The type of actuator is used where high levels of thrust is required to move the valve
A
piston
12
Q
- Gate valves and globe valves require a _________ type actuator
A
linear
13
Q
- Ball valves and plug valves require a _________ type actuator
A
rotary
14
Q
- A direct acting actuator will fail _______ with a loss of supply pressure
A
open
15
Q
- A reverse acting actuator will fail ______ with a loss of supply pressure
A
closed
16
Q
- Name the two main styles of rotary actuators.
A
Rack-n-pinion and Scotch Yoke
17
Q
- Butterfly and plug valves are typically used in ____________ applications.
A
on/off
18
Q
- T/F In a rack and pinion actuator, the linear gear is known as the pinion.
A
False
19
Q
- T/F An oversized valve actuator can cause damage to the stem of the valve.
A
True
20
Q
- In the natural gas industry, _______ valves are typically used for throttling applications
A
ball and globe
21
Q
- In the natural gas industry, ________ valves are typically used for on/off applications.
A
ball
22
Q
- Identify the actuator types below:
A
Scotch Yoke
Piston
Diaphragm
Rack N Pinion
23
Q
- How can restricted–capacity trim parts be helpful for changing flow conditions in an existing control valve?
A
Restricted capacity trim make it possible to select a valve body large enough for increased future flow requirements, but with trim capacity properly sized for present needs.
24
Q
- Rack-and-pinion actuators are typically used for ________ applications
A
on/off
25
1. T/F A controller is used to regulate process variables in an industrial process
True
26
2. Name the three modes of control.
Proportional, Integral, Derivative.
27
3.T/F In a closed loop system, a sensor is used to measure the process variable and provide feedback to the controller.
True
28
4. The desired or command value for the process variable is known as the _____.
Set Point
29
5. _______ control is a control method that initiates a control response that is made in proportion to the magnitude and direction of the error amount between the set point and the measured value.
Proportional
30
6. A proportional controller compares the set point with the process variable value and generates a(n)
Offset error
31
7. What is the output signal equation for proportional control.
Kpxe
32
8. The greater the value of the proportional gain factor Kp, the _____ is the response of the system
faster
33
9. T/F If the proportional gain is too large for the process, the process will oscillate
True
34
10. Proportional band is _______ proportional to gain
inversely
35
11. T/F When sufficient gain is applied, the output will stabilize but will not quite reach the set point.
True
36
12. When controller output exceeds its desired value, it is known as ________.
overshoot
37
13. T/F Integral control is used when an unacceptable amount of offset occurs.
True
38
14. Give an example of integrating (accumulating) a variables value with respect to time
Vehicle odometer
39
15. T/F Integral control basically tells the controller output how fast to move
True
40
16. T/F Integral control determines how much to compensate for the offset
True
41
17. Once the process variable equals the setpoint, integral actions ___
stop operating
42
18. Name the two ways to specify the degree of integral action.
Minutes or minutes per repeat
43
19. Proportional plus integral control is also referred to as proportional plus ____ control.
reset
44
20. When the amount of correction exceeds the capacity of the equipment and the setpoint still can’t be reached, the result is called integral ________.
windup
45
21. T/F Too much integral action will not cause the control loop to oscillate
False
46
22. T/F Derivative control is an expression of a variable’s rate of change with another variable
True
47
23. Derivative control calculates the ratio of a variables change per ____________.
Unit of time
48
24. T/F The purpose of the derivative action is to move the final control elements in a direction to counteract the rapid change by moderating the speed at which the process variable changes
True
49
25. T/F Using derivative control is a good idea when the process variable has small, random, rapid changes in process variables.
False
50
26. Rapid changes in a process variable is known as _______.
Noise
51
27. Derivative control is most commonly used in _____ control loops.
temperature
52
28. The adjustment of control parameters to achieve proper control is called ________.
Tuning
53
29. What is the goal of tuning a PID control loop.
Adjust its output to move the process variable as quickly as possible to the set point, while minimizing overshoot, and the hold the variable steady at the set point without excessive output changes
54
30. The time required to reach the setpoint is known as _______ time.
Response
55
31. A control loop response that results in a process value that drives below the set point is known as ___________.
Undershoot
56
32. To start tuning, one should begin with ___________ control.
proportional
57
33. T/F Integral control is used when an unacceptable amount of offset occurs in a process with proportional control.
True
58
A device used for the control of fluid flow. It consists of a fluid retaining assembly, one or more ports between end openings and a movable closure member which opens, restricts or closes the ports).
Valve
59
A power operated device which modifies the fluid flow rate in a process control system. It consists of a valve connected to an actuator mechanism that is capable of changing the position of a flow controlling element in the valve in response to a signal from the controlling system
Control Valve
60
A a fluid powered or electrically powered device which supplies force and motion to a valve closure member.
Actuator
61
Is mechanically connected to a moving part of a final control element or its actuator, and automatically adjusts its output pressure to the actuator in order to maintain a desired position that bears a predetermined relationship to the input signal. The positioner can be used to modify the action of the valve (reversing positioner), extend the stroke/ controller signal (split range positioner), increase the pressure to the valve actuator (amplifying positioner) or modify the control valve flow characteristic (characterized positioner).
Positioner
62
2. Name the four types of linear motion control valves.
Globe, gate diaphragm, pinch and clamp
63
3. The three types of rotary motion control valves are ball, butterfly, and
Plug
64
4. Name the three types of actuators. _
Pneumatic, electric and hydraulic
65
5. A pneumatic input valve positioner has a ____________ output.
pneumatic
66
6. This form of deadband is also known as slack that results from a temporary discontinuity between theinput and output of a device. An example is looseness of a mechanical connection. _
Backlash
67
7. The rate of flow through a valve under stated conditions is known as _________________________.
Capacity
68
8. T/F A process control loop where information from the process variable is continuously fed back to the controller to provide continuous automatic corrections to the process variable is known as an open loop.
False
69
9. A device that operates automatically by use of an algorithm to regulate a controlled variable is known as a ___________________.
Controller
70
10. The range through which an input signal can be varied without an observable change in the output signal is known as _______________.
Deadband
71
11. The device that implements the control strategy determined by the output of the controller is known as the ______________________
Final Control element
72
12. T/F A force that opposes the motion between two surfaces is known as friction.
True
73
13. The ratio of between output change to input change is known as _________________.
Sensitivity
74
14. T/F The abbreviation for current to pressure input modules is known as E/P.
False
75
15. T/F A process control loop where information from the process variable is continuously not fed back to the controller is known as an open loop.
True
76
16. The closeness to which a curve relating two variables approximates a straight line is known as____________________________.
Linearity
77
17. The desired value of the process variable being controlled is known as ____________________.
Set point
78
18. The internal components of a valve that modulate the flow of the controlled fluid is known as___________.
Trim
79
19. For the globe valve trim characteristics below, label the equal percentage, linear, and quick opening
characteristics.
top curve - Quick Opening
Middle flat- Linear
low curve - Equal percentage
80
20. At the 50% of rated travel, the quick opening valve trim provides _____% of maximum flow.
80
81
21. At the 50% of rated travel, this valve trim provides 18% of maximum flow. _______________.
Equal percentage
82
22. This characteristic of this valve trim typically has the same % of maximum flow as the % of rated travel. (i.e. 30% travel = 30% flow) __________________________________
Linear
83
23. A part of the trim that surrounds the closure member and provides flow characterization is the_______________________.
Cage
84
24. For the valve trims below, identify the equal percentage, linear, and quick opening cages
Linear
Equal Percentage
Quick Opening
85
25. The area of contact between the closure member and its mating surface that establishes valve shut-off is known as the _____________.
seat
86
26. T/F Flangeless control valves are common to rotary-shaft control valves.
True
87
27. The flow control orifice of a control valve is known as a ________________________.
Port
88
28. The most common type of segmented ball valve is known as a ___________________ ball.
V Notch
89
29. A part of the valve assembly used to seal against leakage around the valve disk or stem is known as _______________________________________.
Packing
90
30. A control valve that moves to a closed position when the actuating supply gas source fails is known as a ________________ valve.
Fail-closed
91
31. A control valve that moves to an open position when the actuating supply gas source fails is known as a ________________ valve.
fail-open
92
32. A control valve that stays in its last position when the actuating supply gas source fails is known as a ________________ valve.
fail-safe
93
33. This constant known as Cv is related to the geometry of a valve for a given travel and represents the number of US gallons/minute of 60 Degree water that will flow through a valve with a 1 psi pressure
drop is the _______________________________.
Flow Coefficient
94
34. The quantity of fluid passing through a valve when the valve is in the fully closed position with specified pressure differential and temperature is known as______________________________.
Seat leakage
95
35. Name the six ANSI Leakage Class Designations for Control Valve Seat Leakage.
I
II
III
IV
V
VI
96
36. This ANSI Leakage Class Designations requires no testing
I
97
37. This ANSI Leakage Class Designation requires 45 -60 psig of pressure of air or water between 50 – 125 ◦F applied to the inlet with outlet open to the atmosphere and a maximum allowable leakage of 0.01% of rated capacity. _____________
IV
98
38. This ANSI Leakage Class Designation requires 45 -60 psig of pressure applied to the inlet with outlet open to the atmosphere and a maximum allowable leakage given in bubbles per minute____________.
VI
99
39. A valve with a Class VI ANSI Leakage Class Designation with a 1” has an allowable seat leakage of ______ bubbles per minute.
1
100
40. A valve with a Class VI ANSI Leakage Class Designation with a 2” has an allowable seat leakage of ______ bubbles per minute.
3
101
1. Why are compressed air systems not used at gas pipeline valve settings and measuring stations for instrument supply air?
The remoteness of the valve settings and measuring stations makes them impractical to install pneumatic systems
102
2. Name some of the operating problems that unprocessed natural gas can cause in pneumatic actuated valves
Dirty or wet gas will clog pneumatic controllers and wet air or gas will freeze in the winter months
103
3. What are the two components that are used to dry the gas in dryer canisters? _
Silica gel and activated charcoal
104
4. What are the two typical pressure outputs for an instrument supply system?
35psig spit for actuators requiring 6-30 psig supply pressure and 20 psig for actuators requiring 3-15 psig supply pressure
105
5. Why are catalytic heaters used in instrument supply systems?
High inlet pressures (>1,000 psig) due to the Joule-Thomson effect of 7° F temperature reduction occurs for every 100 psig drop and they are flameless
106
6. In a moisture indicator, this color indicates that the desiccant is saturated and needs changed out.
Pink Color
107
7. Why do some instrument supply systems have duplicative filters and regulators? _
So that flow can continue should maintenance be required on one of the filters or regulators or as a standby backup.
108
1. What function does a pneumatic controller perform?
Use regulated gas supply pressure to control the operation of mechanical devices, such as valves
109
2. Name two process variables that can be controlled with a pneumatic controller.
Levels and Pressures
110
3. What are the two typical output pressure ranges of pneumatic controllers?
3-15 psi or 6-30 psi
111
4. Name the three types of process signal measuring elements that are can be used with the controller.
Bellows, Helical bourdon tube and spiral bourdon tube
112
5. What part of the controller shows the scale range of the controller?
Dial
113
6. The __________ measures the difference between the measurement pointer and the setting index position.
Differential linkage
114
7. The __________ allows the operator to manually operate the pneumatic controller
Auto/manual transfer system
115
8. Name the part of the controller that adjusts the output pressure when the controller is set to “Manual”.
Regulator
116
9. What part of the pneumatic controller shows the true value of the process variable? _
Measurement Pointer
117
10. To understand what is happening in a process, what three pieces of information that is available on a pneumatic controller should a technician should look at?
The Set point index, the measurement pointer and the output pressure to the valve actuator
118
11. To make an adjustment to the minimum range of the pneumatic controller, you should use the _____ adjustment
Zero
119
12. To make an adjustment to the maximum range of the pneumatic controller, you should use the _____ adjustment.
Span
120
1. Where are positioners typically mounted on linear sliding stem control valves?
On the side-yoke or top casing of the pneumatic actuator
121
2. Name three reasons for using a valve positioner
Increase control system resolution, Allow for split ranging, one controller for 2 valves. Overcome seation friction in rotary valves
122
3. Name the three types of positioners.
Pneumatic, Analog I/P Postioners and Smart or Digital Positioners
123
4. An I/P positioner uses __________________ instead of air supply as the input signal.
electrical current
124
5. The electronic signal conversion is ________ in a smart positioner
digital
125
6. Valve hysteresis throughout the valve stroke in a control valve configuration without a positioner is __________ than a control valve configuration with a positioner.
Significantly higher
126
7. Name five reasons why instrumentation and accessories are added to a control valve. _
Improve process control, improve safety for the process or personnel, improve valve performance or speed of response, Monitor or verify the valve responsiveness and diagnose potential valve issues
127
8. Positioners are typically used when valves are used in ____________ applications.
throttling
128
9. An I/P positioner uses a _________ mA DC signal to modulate the control valves.
4 to 20
129
10. T/F With a digital valve positioner, the microprocessor enables diagnostics and two-way digital communication to simplify setup and troubleshooting.
True
130
11. Provide two examples of data feedback that is provided by the microprocessor to the control system.
Run, analyze, and store diagnostic tests as well allowing the positioner to communicate with the control system via a digital signal
131
12. Name two common protocols used by digital positioners.
HART communication and FOUNDATION fieldbus
132
13. This communication protocol uses a digital signal superimposed over a 4 to 20 mA DC control signal.
HART communication
133
14. An I/P transducer converts a current input into a proportional _________________ output.
Pressure
134
15. What is the purpose of a volume booster?
Used to provide additional pneumatic output capacity to a valve assembly
135
1. A properly sized control valve should operate at between ________ percent open at the maximum required flow rate
60 to 80
136
2. A properly sized control valve should operate at not less than ____ % open at the minimum required flow.
20
137
3. T/F Commonly, the control valve is too large for the application.
True
138
4. With an oversized valve, small changes in valve position will cause _____ changes in flow.
large
139
5. T/F Valve sizing and selection for control valves in gas service must include noise calculations.
True
140
6. Inherent characteristic of a control valve represents the relationship between valve flow capacity and _______ when there are no system effects involved.
Valve opening
141
7. T/F The majority of fluid process systems include a significant amount of pipe and other pressure consuming elements such as tees, elbows and valves.
True
142
8. The installed characteristic of an equal percentage valve in a system with a lot of pipe is not linear but has a slight ____ shape
S
143
9. A process system with a lot of piping should use a control valve with a(n) _____________ characteristic.
Equal percentage inherent
144
10. A process system that has very little pipe should use a control valve with a(n) _______ characteristic.
Linear inherent
145
1. T/F A standard port ball valve has a flow path that is the same size as the valve’s pipe size
False
146
2. How many shafts are used to support the ball in a Fisher V250 ball valve?
two
147
3. What is/are the name(s) of the shaft(s) called in Question #2 above? _
follower shaft and drive shaft
148
4. What are the two types of soft seal designs for ball valves?
Single and double
149
5. The seal face is a ball valve is protected from contact with the flowing media by a
Metal seal protector ring
150
6. If you have a ball control valve with bidirectional flow, you should select a ______ seal design.
double
151
7. T/F Advantages of a ball control valve include high flow capacities and low pressure drop across the valve.
True
152
8. Name the three basic styles of butterfly valves.
Conventional, lined and high-performance
153
9. Pressure drop across a butterfly valve is _________ the pressure drop through a globe valve.
less than
154
10. T/F A wafer style butterfly valve requires care in installation because they must be perfectly centered between two flanges
True
155
11. T/F A conventional butterfly valve does not provide a tight shutoff
True
156
12. What feature does a high performance butterfly valve have that a conventional butterfly valve does not have?
An offset (eccentric) disk used in the construction which allows for pressure-assisted seals
157
13. How is the sealing action accomplished in a high performance butterfly valve?
Allows the process pressure behind the seal to provide the force for the seal to press against the sealing edge of the disk
158
14. Name the two basic types of plug valves. _
Lubricated and non-lubricated
159
Correct position to install a valve?
Upside up
160
16. T/F Flanges, piping and equipment must line up square and true with the valve without putting undue stress on the valve.
True
161
1. T/F When gas or steam flows through a control valve, noise is generated.
True
162
2. T/F Noise from a control valve may be loud enough to cause hearing damage to those who are nearby.
True
163
3. When gas flows past a restriction in the control valve, the velocity _______.
increases
164
4. T/F If the pressure drop across the control valve is high enough, the turbulence will generate sound waves which will move down the pipe with some coming through the pipe wall
True
165
5. Name the two strategies for reducing control valve noise.
Source Control and Path Control
166
6. Define “pressure drop staging” noise reduction.
Instead of taking then entire pressure drop in one step, the pressure drop is divided up into two or more steps.
167
7. Doing something to the valve to make it less noisy is known as ____ control.
source
168
8. Small reductions in velocity have a small effect on reducing valve noise.
True
169
10. For the “flow division” noise reduction method, every time you double the number of openings, you reduce the noise by ___dBA.
3
170
9. Define “flow division” noise reduction
Instead of flowing through a single opening, the flow is divided up so that it pass through several openings in parallel
171
11. T/F Using the smaller opening associated with “flow division” actually shift the noise to higher frequencies.
True
172
12. Globe control valve using flow division with one stage noise trim can achieve noise reduction of ___dBA noise reduction.
10 to 15 dBA
173
13. Multiple stage flow dividers can achieve ____ dBA noise reduction.
15 to 25
174
14. Name the three types of path control method that can be used to control noise.
Distance, heavy wall pipe and thermal or acoustic insulation
175
15. Thicker pipe walls attenuate ____ noise as it passes through the pipe wall compared to thinner pipe walls.
more
176
16. Name a disadvantage of using heavy wall pipe to control noise.
Can become cost prohibitive as it is expensive
