Test 1 Flashcards
1
Q
- PD meters are __________ measurement devices.
A
Direct
2
Q
- PD meters are considered the best technology for applications requiring
A
Accuracy, stability, and Relability
3
Q
- Name two types of positive displacement meters. ________ and _______
A
Diaphragm & Rotary
4
Q
- Explain the essential principle of operation of a positive displacement meter
A
A discrete and well-defined portion of the fluid carried from inlet to outlet without loss or mixing with the remainder of the fluid.
5
Q
- Diaphragm meters have ________________ measurement compartments.
A
Fixed volume or 4
6
Q
- What causes the measurement compartments on a diaphragm meter to alternately fill with gas at the inlet and then empty at the outlet.
A
Pressure Drop
7
Q
- Diaphragm meters are used in applications where maximum flow is ______ CFH or less and a ______ turn down is required.
A
10,000, high
8
Q
A diaphragm consists of _____ chambers. _______ diaphragm chambers on the inlet and outlet side and the _____inlet and outlet chambers of the meter body.
A
four, two, two
9
Q
- Explain how the flow of gas through a diaphragm meter facilitates the measurement of gas in the meter.
A
The passage of gas through the meter creates a differential pressure between the two diaphragm chambers by compressing the one on the inlet side and expanding the one on the outlet side. This action alternately empties and fills the four chambers.
10
Q
Diaphragm meters are generally rated in ____________ and sized for a pressure drop of ___________ inches of water.
A
units of cubic feet/hr, .5-2
11
Q
- Diaphragm meter accuracy is approximately ___________ over a 200:1 flow range.
A
+/- 1%
12
Q
Name the parts that form the fixed-volume compartments for a rotary meter.
A
Pair of hourglass-shaped impellers that form the fixed volume compartments.
13
Q
Explain how the gas goes from the inlet to the outlet of a rotary meter.
A
When downstream demand initiates the flow of gas, the impellers rotate to receive a fixed volume of gas at the inlet. Then they discharge at the outlet.
14
Q
Rotary meters are used in applications where gas flow is between ____ CFH and ___________ CFH.
A
800, 102,000
15
Q
Explain why it is important for the gas to be free of particulate matter and the meter mounted so it is not in a bind.
A
The rotors have a very small gap between them and tight tolerances on impellers and meter body. Particulate matter and being in a bind can distort the tight tolerances of the impellers.
16
Q
T/F Rapidly changing flow rates may damage rotary meters or downgrade their accuracy.
A
True
17
Q
- Provide a short Definition of pulsation.
A
Pulsation is a periodic fluctuation in local pressure and velocity that occurs throughout the piping system or network
18
Q
- T/F Pulsations travel in acoustic waves only downstream from the source.
A
False
19
Q
- Traveling waves of pulsation can be reflected from “closed” ends of a piping network. Provide three examples of “closed” ends on a pipeline.
A
Capped or flanged ends of headers, closed branch line valves & Terminations of gauge or drain lines
20
Q
- Traveling waves of pulsation can be reflected from “open” ends of a piping network. Significant and sudden diameter changes in a piping network can approximate the characteristics of an “open” pipe end. Provide three examples of instances in a piping system where these types of changes occur.
A
Scrubbers, large headers, or locations where a small branch line connects to a larger diameter pipe have acoustic characteristics closely approximating those of truly “open” pipe end.
21
Q
- At certain conditions traveling pulsation waves are reflected to form standing waves that reinforce pulsation amplitudes. This condition is known as ___________________.
A
Acoustic Resonance
22
Q
- T/F Acoustic resonance occurs at the resonant frequency of the pipe at operating conditions.
A
True
23
Q
- What three things in a pipeline determine the frequency and the fundamental wavelength of a pulsation acoustic wave?
A
The relationship between the speed of sound of the flowing medium, the pipe length and the pipe end conditions.
24
Q
- List four sources of pulsation in a piping system.
A
Reciprocating compressors, pressure regulating or flow control valves, rotary screw or booster compressors and fluidic instabilities, such as slug flow.
25
9. T/F Rotary meters are not normally subject to errors in pulsating flow, but can adversely affect nearby meters of other types.
True
26
Coriolis meters can be severely affected by pulsation when the pulsation frequency _______________________________________________.
synchronizes with the mechanical natural frequency
27
T/F Ultrasonic meters cannot be adversely affected by pulsation.
False
28
12. T/F Depending on the frequency of the pulsation, the adverse effects of the pulsation can travel from 1-20 miles from the source.
False Over 20 miles
29
13. T/F Installing scrubbers or large pipe headers has no impact on pulsation.
False
30
1. Name three common factors that affect positive displacement meters.
Pressure, temperature and specific gravity effects.
31
2. Volumes measured at line conditions of pressure and temperature are known as ___________________________.
Uncorrected volume
32
3. Volumes converted to equivalent volumes at standard conditions are known as ___________________________________.
Corrected volume
33
4. Provide the equation and explain the components that compensate for the effects of pressure on uncorrected volume.
34
5. Provide the equation and explain the components that compensate for the effects of temperature on uncorrected volume.
35
6. Provide three events that could occur causing a meter’s accuracy to shift.
Meters can become damaged or experience deterioration of sensitive measuring components.
Dirt and debris can accumulate in the meter.
The inputs into flow computers and other electronic devices can be changed by mistake, causing errors in measurement.
36
7. The method and device used when proving positive displacement meters is determined by ___________________________ and __________________
The type of meter to be proved, company policy
37
8. The three standards setting the guidelines for positive displacement meters are:
ANSI B109.1 Diaphragm - Type of gas Displacement Meters (Under 500 Cubic Feet Per Hour Capacity)
ANSI B109.2 Diaphragm - Type Gas Displacement Meters (500 Cubic Feet Per Hour Capacity and Over)
ANSI B109.3 Rotary - Type Gas Displacement Meter
38
9. Name the three conventional prover types.
Transfer, bell or sonic nozzle
39
Identify the relationship of the gas being measured by a “fast” and “slow” meter to the actual displaced volume being measured.
A fast meter is over registration of the actual displaced volume while a slow meter is an under registration of the actual displaced volume.
40
11. Show how Percent Proof and Percent Accuracy are mathematically determined.
41
What is the relationship between percent proof and percent accuracy.
Percent proof is the reciprocal of percent accuracy.
42
T/F A diaphragm meter must be tested by flowing a quantity of gas through the meter which causes the meter to make one or more complete revolutions of its mechanism.
True
43
14. The Percent Error of a meter flowing at 95% Proof is:
5.3
44
The Percent Error of a meter flowing at 107% Proof is:
-6.5
45
16. Explain the principle behind how a sonic prover works.
Work on the principle that when gas is flowing through a well-rounded orifice or nozzle, the velocity increases as the pressure differential across the orifice increases until it reaches critical also called sonic velocity.
46
What is the definition of sonic velocity and when is it reached during the sonic prover process?
The maximum speed at which gas or air travels. It is reached when the absolute pressure on the upstream side of The orifice equals or exceeds approximately twice the absolute pressure on the downstream side.
47
Name the variables that are measured and used in the sonic prover process.
The gas’ specific gravity, the gas’ temperature at the prover and the meter, the pressure of the gas on the upstream side of the orifice and at the meter, and super-compressibility of the gas.
48
19. The calculation of the compressibility factor used in sonic provers is based on what Standard?
The AGA 8 detailed composition standard
49
What is the number stamped on a sonic nozzle called and what does it indicate?
Stamped with a number call the standard time that indicates how long it will take the orifice to pass 1 cubic foot of Air at 60°F and a pressure of 10 psig
50
List the advantages of using a sonic prover.
Relatively inexpensive, is easy to use and connect, and does not require a lot of extra equipment to operate. It also uses gas in the system to perform the measurement, eliminating the need for the measurement technician to provide compressed air or another gas for the test.
51
22. List the disadvantages of using a sonic prover.
Since it doesn’t use system gas, it requires the accurate measurement of a number of different parameters. An error in any of these can result in an error in the test. Also, due to the nature of the test, interpolation errors can lead to faulty results and since the test uses gas, which is often odorized, it results in odorized gas being released into the atmosphere.
52
23. A sonic prover is a “fixed=flow” device. Explain what this means and its impact on developing an accuracy curve over the operating range of the meter being tested.
It means that a nozzle or a critical-flow orifice or a given throat diameter (bore) gives one, and only one, flow rate a particular pressure. Therefore, to develop an accuracy curve over the operating flow range of the diaphragm meter, for example, several nozzles or orifices of different throat sizes must be used.
53
24. Explain the principle of transfer proving.
Consists of testing a meter against a master or reference meter of know accuracy.
54
What two things must be watched for and prevented when performing a transfer prover test on a meter to insure the calibration is accurate?
Ensure that pulsating flow or swirl conditions are not transmitted to the test meter.
55
1. Although the basic measuring concept of diaphragm has not changed since their development in 1843, name three “modern day” changes to the meter that have improved performance.
Structural arrangement of parts, selection of materials and test parameters
56
2. T/F Each stroke of the diaphragm in the meter displaces a fixed volume of gas.
True
57
3. The diaphragms in the meter operate 90° out of phase so that when one is fully stroked the other is at mid-stroke. What benefits does this provide for the meter?
Provides a smooth flow of gas to the meter outlet and insures that the meter will always start regardless of position.
58
4. What is the purpose of the sliding valves above each diaphragm?
Direct the flow of gas in and out of the case and diaphragm compartments.
59
5. T/F The stroke of the diaphragm is controlled by linkage in the upper part of the meter and a flag rod that extends down into the diaphragm compartment.
True
60
6. Explain the relationship between meter accuracy and meter proof.
Gas meters are calibrated in terms of percent “proof” which is the inverse of accuracy
61
7. Explain why differential pressure is required to drive a diaphragm meter at a given flow rate.
It’s required to overcome the small friction forces and pneumatic losses in the meter.
62
8. T/F An increase in differential pressure increases meter accuracy.
False
63
9. T/F An internal leak will decrease the meter accuracy.
False
64
Explain a method to find an external leak on a diaphragm meter.
Submerging the meter in water and pressurizing it up to its working pressure. A gasket leak will appear as a bubble on the edge of the gasket.
65
It is necessary to compensate for the changes in gas density due to temperature by varying the __________________. This is accomplished by _____________________________________________________________.
speed of the meter, Changing the stroke of the diaphragm according to the gas temperature.
66
What is the function of the Temperature Compensated Tangent in a diaphragm meter?
To lengthen or shorten the stroke of the diaphragms by automatically changing the sit length in response to change in temperature. This is accomplished by use of a bimetallic element which expands and contracts in proportion to the absolute temperature of the gas.
67
1. Why is it important to test and perform maintenance on PD meters?
Ensures an accurate gas delivery record
68
2. Name five factors that are used to determine a meter inspection program.
Tariff, DOT Regulations, Bureau of Ocean Energy Management, Regulation and Enforcement, Company Policy and either a gas purchase contract or gas transportation agreement.
69
3. T/F Other factors that used in determining meter inspection programs are the volume of gas being measured and the type of meter installed.
True
70
4. T/F A diaphragm meter must be tested or proved to determine the accuracy of the meter.
True
71
5. Name six factors that can affect the accuracy of a diaphragm meter.
Internal friction that increases the meter differential, maintaining constant diaphragm displacement, External Leaks, Internal Leakage, Internal Wear and Liquid accumulation in the meter body.
72
6. T/F It is a good idea to perform maintenance on a diaphragm meter even if the accuracy test is good.
False
73
7. If the diaphragm meter accuracy test is not good, list some steps that can be done to correct any issues.
Remove the index counter and check to see if the drive dog is turning. Bypass, isolate and blow down (from the upstream side if possible) the meter. Open all valves slowly, not exceeding 60 psi per minute pressure increase. Check the condition of all gears and linkages. If worn or stripped, replace them. if not, the valve plate assembly (diaphragm and associated parts) is the problem and should be replaced.
74
8. How is an adjustment done to a diaphragm meter?
Changing the length of the two tangent posts.
75
9. T/F It is a good idea to perform maintenance on a diaphragm meter even if the accuracy test is good.
False
76
10. T/F Rotary meters do not require the oil to be routinely checked and changed.
False
77
11. T/F Rotary meter will generally fall into one of two categories: with internal bypass and without internal bypass.
True
78
List the steps normally taken when a rotary meter prover test is unsuccessful.
Flush meter with oil, clean vanes and run prover again. If that still doesn’t work, replace meter/cartridge in accordance with vendor manual. Prove. Return to service.
79
T/F Foreign objects blocking the rotor can cause a prover test to fail on a rotary meter.
True
80
How soon should a rotary meter be replaced If it cannot be proved successfully?
As soon as possible.
81
1. T/F As gas flows through a rotary meter the impellers turn trapping a known volume of gas.
True
82
2. The impellers and the measuring chamber wall ________ touch and are separated by gaps measuring on average 0.003”.
do not
83
3. What is the simplest way to size a rotary meter?
Add together the total connected load at the minimum pressure.
84
4. T/F Rotary meters are designed to operate at 90% capacity.
False
85
5. What should be done if a selected rotary meter is expected to run over 100% capacity on a regular basis?
Wise to use the next larger size meter.
86
6. If a meter could be subjected to severe over-speed the use of a _____________________________ should be considered.
Restricting orifice plate
87
7. Restriction plates are sized to cause _______________________ at approximately _______ of the meter capacity.
critical flow, 120%
88
8. The restricting orifice plate size for an 8C175 meter is _______ and the restricting orifice plate size for a 5M175 meter is _____________.
17/64, 23/32
89
Rangeability measures the
Ability of a rotary meter to accurately perform throughout its rated capacity.
90
9. As the rotary meter size increases the restricting plate size _______________.
increases
91
11. Start rate is
For a meter is the flow rate at which a meter will begin and continue to turn.
92
12. The meter accuracy at the start rates can vary widely, but are generally are between _________________________________.
70% and 90%
93
T/F The meter stop and start rate are the same.
False
94
The differential, or pressure drop, across a rotary meter is an important component of the design criteria. Low differential rates indicate what two things?
All meter parts are working efficiently and friction within the meter is at a minimum.
95
The basic rule of thumb for differential testing is to address the condition of a meter when the differential across a meter has increased ___________
50% or more
96
16. T/F A rotary meter differential test provides the accuracy of the meter.
False
97
The differential pressure across a rotary meter can be affected by what four factors?
Line pressure, Flow rate, Specific gravity and Internal friction.
98
18. Not having current differential meter tests can impact a company in what ways?
It’s capital budget dollars, its LAUF gas, Regulatory compliance and Customer complaints.
99
The ANSI B109.3 standard for rotary meters mandates that new meters meet an accuracy range of _________ at flow rates representing ____________________________________________________________.
+/- 1%,
10% through 100% of capacity.
100
What constitutes an “accelerated life test” for a rotary meter?
Consists of meters running at 100% of rated capacity for 4,000 hours. At the end of this test the meter must still be accurate to +/- 1% at 10% through 100% of capacity.
101
21. List the six precautions that should be taken when installing a rotary meter.
Piping stress, gas conditions, meter placement, Check for rotation, slowly pressurize and snap on-off Loads
102
List the four main maintenance items needed for Rotary meters.
Oil Level and Color, Differential Pressure Testing, Field Prover Tests and Temperature Compensated Cycle Test
103
The addition of a transmitter to an electronic meter corrector or flow computer allows the meter to measure______________________________ on its own.
Flow rate, differential pressure, metering (line) pressure and flowing temperature
