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Gasm 152 > Test 2 > Flashcards

Test 2 Flashcards

1
Q

T/F Coriolis flowmeters can only measure liquids.

A

False

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2
Q

T/F The density of a liquid is almost independent of the liquid conditions.

A

True

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3
Q

The density of a gas is dependent on what 3 things?

A

Pressure, temperature and, to a lesser extent, gas composition

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4
Q

Define the energy flow rate for volume and mass.

A

The volume flow rate multiplied by the energy content per unit of volume or mass flow rate multiplied by the energy content per unit mass.

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5
Q

T/F Coriolis flowmeters offer direct mass measurement.

A

True

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6
Q

T/F Due to how a Coriolis flowmeter operates (Coriolis force) changes in temperature, pressure, density, viscosity and flow profile have a large role when measuring flow.

A

False

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7
Q

A Coriolis flowmeter consists of a sensor, a transmitter and in many cases, peripheral devices. At a high level, the sensor in a Coriolis flow meter performs what function?

A

Flow rate, density and temperature

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8
Q

At a high level, the transmitter performs what function?

A

Provide sensor information as outputs, acting like the brain of the system to provide a display, basic menu access, and outputs to interface with other systems.

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9
Q

At a high level, peripheral devices perform what functions?

A

Provide monitoring and alarm or additional functionalities, such as batch control and enhanced density functions

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10
Q

List the key design aspects of the Coriolis flow tube.

A

The diameter, the tube wall thickness, the material of construction, the overall length, and the shape.

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11
Q

The different designs of the Coriolis flow tube incorporate different geometries. What is the purpose of the flow tube geometry?

A

The majority of designs try to employ a geometry that will magnify the effect of the Coriolis forces on the flow tubes to generate a larger signal.

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12
Q

List the 8 components of a Coriolis flowmeter.

A

Flow Tubes, casing, drive coil, flow detectors, temperature detector, flow splitter, processor/transmitter, flowmeter peripherals

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13
Q

The flow tubes carry the process fluid and are mostly constructed of what two materials?

A

Stainless steel or nickel alloy steel

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14
Q

What is the purpose of the casing on a Coriolis flowmeter?

A

Protects the electronics and wiring from external corrosion while providing a redundant(or secondary) containment of the process fluid.

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15
Q

T/F The drive coil is energized to keep the flow tubes vibrating at their natural frequency.

A

True

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16
Q

Flow detectors and their magnets are electromagnetic detectors located on each side of the flow tube. What role do the flow detectors play in determining the mass flow through the meter?

A

Produce a signal that represents the velocity and position at that point on the vibrating tube and measuring the phase difference between these signals, mass flow is determined.

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17
Q

The temperature detector is an RTD. What does RTD stand for?

A

Resistance Thermal Device

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18
Q

What is the purpose of the flow splitter?

A

It’s a component that is located in the inlet process connection and connected to the flow tubes. The flow splitter divides the process flow evenly between the two flow tubes.

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19
Q

The Coriolis drive coil, flow detector coils and RTD element is routed to the transmitter. What is another name for the transmitter?

A

Processor

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20
Q

Name seven things that flowmeter peripherals can provide from a Coriolis flowmeter.

A

Mass flow, temperature, density, volumetric flow data, mass or volume totals, alarm outputs and controls valves or other control components

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21
Q

T/F Coriolis flowmeters are not used to control valves or other control components in a system.

A

False

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22
Q
  1. A Coriolis meter is comprised of two main components, a _________________ and a _________________________.
A

sensor (primary element), transmitter (secondary element)

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23
Q

T/F Coriolis meters directly infer the gas mass flow rate by sensing the Coriolis effect on a vibrating tube(s).

A

True

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24
Q

T/F The direct relationship between the pressure drop and flow range with the actual flow area through a Coriolis meter means a Coriolis meter will typically be larger than a turbine or orifice meter having similar pressure drops at flowing pressures in the 300 ANSI class and above.

A

False

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25
Q

1-7 Left to Right

A

1.Process Connection Flange
2. Flow Tubes
3. Left Pickoff Coil and Magnet
4. Drive Coil and Magnet
5. Right Pickoff Coil and Magnet
6. RTD
7. Process Connection Flange

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26
Q

The twisting of the flow tubes created by the Coriolis force creates a ___________________ between the signals generated by the two pick-off coils.

A

phase shift

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27
Q

The vibration frequency of the flow tubes is proportional to the flowing _______________ of the fluid being measured.

A

density

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28
Q

The phase shift between the signals generated by the pick-off coils is directly proportional to ______________________________.

A

mass flow rate

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29
Q

T/F The “flowing” density measured by the Coriolis meter is used for gas flow measurement purposes.

A

False

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30
Q

Equations and methods for the conversion of mass to volume are documented in what two standard documents?

A

AGA Report Number 11, Measurement of Natural Gas by Coriolis Meter and AGA Report Number 8, Compressibility Factors for natural Gas and Other Hydrocarbon Gases

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31
Q

The typical operating temperature range of a Coriolis meter is ___________ to ___________________.

A

-400 F (-240 C), +400 F (+200 C)

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32
Q

T/F Flowing gas temperature is not required for the measurement of mass with a Coriolis meter.

A

True

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33
Q

The ______________________ of a Coriolis meter is caused by the stiffening of the Coriolis flow tubes as the fluid pressure in them increases.

A

flow pressure effect

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34
Q

T/F Due to the flow splitter and newer designs any rate of change concern is removed for Coriolis meters.

A

True

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35
Q

Erosion due to high velocity gas flow normally is not a concern for Coriolis meters, but can be an issue if__________________________ are present in the gas flow stream.

A

abrasive contaminants

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36
Q

Coriolis meters are sensitive to pulsations at the _____________________ of the meter’s flow tubes.

A

resonant frequency

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37
Q

Coriolis meters typically operate at resonant frequencies above ______ Hz.

A

100

38
Q

T/F An out of specification zero shift caused by the build-up of debris in the meter flow tubes impacts the entire flow range of a Coriolis meter.

A

False

39
Q

T/F Coriolis meters are bi-directional meters.

A

True

40
Q

T/F Based on independent testing, flow conditioning or minimum lengths of upstream/downstream straight pipe is not required for Coriolis meters.

A

True

41
Q

As a common practice most Coriolis manufacturers capitalize on the economics and high stability of a _____________ calibration.

A

water

42
Q

To inspect or re-zero a Coriolis meter, ______________________________ of the meter should be established.

A

thermal equilibrium

43
Q

Describe the Coriolis Effect as it applies to a Coriolis flowmeter and the flow of fluid through the flow tubes.

A

The substance to be measured runs through a tube that is caused to vibrate in a perpendicular direction to the flow. Fluid forces running through the tube interact with the vibration, causing it to twist (I.e. deflect): the greater the angle of the twist, the greater the flow.

44
Q

What relationship is used in a Coriolis flowmeter to compute the amount of flow?

A

The mount of twist in the tube proportional to the flow in the tube.

45
Q

Name the main components of a Coriolis flowmeter.

A

Flow tubes, a driving mechanism for oscillating the flow tubes, and flow detectors mounted on either side of the driving mechanism for measuring the time or phase difference between the two sides of the flow tubes. Flow Splitter

46
Q

T/F The tube sections between the inlet and the driving mechanism will always resist the driver and the tube sections between the driving mechanism and the outlet will always assist the driver.

A

True

47
Q

What force is used to cause the flow tubes in a Coriolis flowmeter to vibrate?

A

Magnetic attraction caused as alternating current energizes the coil which causes a pulsating attraction to the magnet

48
Q

T/F The detector coils and the magnets of the flow detectors are mounted on opposing flow tubes.

A

true

49
Q

As each coil moves through the uniform magnetic field of the adjacent magnet. The voltage generated creates a ____________________.

A

Sine Wave

50
Q

The sine waves generated by the flow detectors represent

A

Represent the motion of one tube relative to the other

51
Q

When there is no flow in the meter, the sine waves are in phase and there is no

A

Coriolis Effect, or twisting motion, imparted on the flow tubes.

52
Q

Explain how the Coriolis Effect works on the inlet and outlet legs of the meter when fluid is moving though the meter.

A

The mass flow moving through the inlet legs of the flow tubes generates a Coriolis force that resists the vibration of the flow tubes. As the mass flow moves through the outlet legs, the Coriolis force adds to the vibration of the flow tubes. It is the opposing direction of the Coriolis force between the inlet and outlet legs that results in the twisting motion that is used to measure mass flow rate.

53
Q

The time delay between the two sine waves caused by the twist in the flow tubes is called ___________ and is measured in ______________.

A

Delta - T, microseconds

54
Q

Fluid flow rate is ___________ proportional to Delta-T.

A

always directly

55
Q

Delta-T is a function of both ______________ and ___________________.

A

the phase difference, the frequency of the sine wave signals

56
Q

The flow calibration factor contains two components.

A

the first component is the proportionality constant between mass flow rate and measured Delta-T. The second component is a constant used to compensate automatically for changes in the temperature of the flow tubes.

57
Q

The flow tube temperature affects the _______________ of the tube material and is compensated for in the __________________ factor.

A

the stiffness, Flow Calibration

58
Q

T/F Volume flow measurement is accomplished by dividing the instantaneous flow measurement by the simultaneous density measurement.

A

True

59
Q

Density is defined as

A

mass per unit volume or mathematically as ρ = m/V
ρ (rho) is the density
m is the mass
V is the volume

60
Q

In a Coriolis flowmeter the volume of fluid in the flow tubes is constant. How is it that the mass of the fluid in the tubes changes?

A

The only way the mass of the fluid can change is if the density also changes.

61
Q
  1. T/F Tube period is the reciprocal of natural frequency.
A

True

62
Q

Coriolis flowmeters measure density by measuring _______________.

A

tube period in microseconds per cycle

63
Q

Fluid density is ___________ proportional to tube period.

A

directly

64
Q

When a Coriolis flowmeter is used to measure gas density it is called a ______________.

A

densitometer

65
Q

Density is often used interchangeably with ______________.

A

specific gravity

66
Q

Specific Gravity (SG) is defined as:

A

As the ratio of the molecular weight of a given sample to an equivalent volume of standard air. SG=D1/D2

67
Q

Measurements of density and specific gravity must be corrected for variations in _________________.

A

temperature

68
Q

As the mass of the process fluid increases, the natural frequency of the flow tubes _________________.

A

decreases

69
Q

As the mass of the process fluid decreases, the natural frequency of the flow tubes _________________.

A

increases

70
Q

Most Coriolis flow tube designs aim to magnify the Coriolis force by the design of ________________________________.

A

The geometrical form of the flow tubes.

71
Q

The larger the Coriolis Effect becomes the larger the __________________ making it easier to determine mass flow.

A

the time or phase difference (Delta-T)

72
Q

T/F The need for the magnification of the Coriolis Effect has disappeared due to the efficiency of today’s electronics.

A

True

73
Q

What impact does the compact tube design on tube oscillation frequencies and why is this an advantage in operating the meter?

A

Shortens the tube length. Higher oscillation frequencies have the advantage of a better decoupling performance from pipeline vibrations and and external disturbances, which are predominantly in the 50 Hz to 180 Hz range.

74
Q

The main reason for using bent tubes in a Coriolis flowmeter is for _______________________.

A

thermal expansion of the measuring tube

75
Q

Why do commercially available Coriolis flowmeters with straight tubes use materials other than stainless steel?

A

Titanium or zirconium materials offer a small temperature expansion coefficient. With these materials, even great temperature differences between the measuring tube and the casing results only small additional axial stress as well as higher stress limits vs stainless steel.

76
Q

T/F A well-designed flow profile is a requirement for the design/use of a Coriolis flowmeter.

A

False

77
Q

Why is it not a good idea to use the dual flow tube design?

A

They require flow splitters and are not recommended for applications with fluids that are prone to plugging

78
Q

The single-tube double loop design flowmeter provides the same advantages as the dual-tube design without employing flow splitters. List the disadvantages of this design.

A

Increased pressure loss and easy drainage of the instrument is impossible

79
Q

How many flow detectors does a Coriolis flowmeter require and where are they located on the flow tubes?

A

Two flow detectors located at the inlet and outlet sections.

80
Q

What are the advantages of the electrodynamic sensors used in todays flowmeters?

A

Very good phase accuracy and high reliability

81
Q

In a Coriolis flowmeter, one temperature sensor is used to measure the temperature of the process fluid. Why is a second temperature sensor needed?

A

Temperature difference between the flow tube and the casing results in an axial force so it is needed to adjust the flow meter reading for this effect.

82
Q

On a gas installation, why is the sensor mounted at a high point in the piping in a vertical (tube/flag up) configuration?

A

Allows any liquid in the flow stream to drain from the meter, ensuring proper operation.

83
Q

T/F Concentric alignment of companion pipe flanges with the sensor inlet/outlet process connections is important when installing a Coriolis flowmeter.

A

True

84
Q

T/F A gasket protrusion has no impact on a Coriolis flowmeter installation.

A

False

85
Q

Why should welding not be done in the immediate area of the sensor?

A

Prevents possible internal weld scale from entering the sensor which could cause plugging.

86
Q

T/F Coriolis flowmeters should be installed at least 3-4 feet from transformers, motors or other sources of electromagnetic induction.

A

True

87
Q

Why is it important to make sure the hazardous area specified on the sensor approval tag is suitable for the environment in which the sensor will be installed?

A

Failure to comply with the requirements for intrinsic safety in a hazardous area could result in an explosion.

88
Q

When are strainers or separator type filters needed when installing a Coriolis flowmeter?

A

Recommended when the presence of damaging foreign material in the gas stream can be anticipated.

89
Q

Name four things that can affect the accuracy of a Coriolis flowmeter.

A

Dirt and trash can accumulate in the piping, affecting flow conditions. The inputs into flow computers and other electronic devices can be changed by mistake, causing errors in measurement. Any change in density, viscosity, pressure or temperature can influence a shift in the number of pulses produced per unit volume. Field installation effects can affect the operation of the meter.

90
Q

What is the difference between a “primary” and “secondary” proving device.

A

A primary device is a volume device such as the bell or volume prover that has had its volume checked and verified against a standard such as NIST in the United States. A secondary device is a device that has been checked against a primary device and is often used to prove another meter.

91
Q

A transfer prover system consists of a _____________ with the field ____________ placed in _____________.

A

master meter, Coriolis meter, series

92
Q

T/F A transfer prover system can be used to calibrate field meters brought into a shop or the master meter prover can be taken to the field.

A

True

Gasm 152 (2 decks)

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