Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
61 Cards in this Set
- Front
- Back
|
What two ways does level indication occur? |
Point level detection and Continuous level detection |
|
|
What is level control? |
The prescribed readings dealing with indication, alarming and control level |
|
|
What does LAL stand for? |
Level Alarm Low, it's found by a point detection indicator |
|
|
What are some examples of point level indicators? |
-Conductivity Probes -Ultrasonic sensor -Capacitance probe -Radiometrics |
|
|
What two ways can both continuous and point level indication be measured? |
The direct method and the indirect/inferential method |
|
|
What's a sight glass? |
A device that provides visual indication of level in a vessel through a glass tube connected to the tank |
|
|
What's the sight glass also known as? |
The gauge glass |
|
|
What's the simplest method of detecting level? |
Conductive level detection (Only used for point level detection) |
|
|
What's Capacitance level detection? |
A detector that works on the principle of capacitance that two plates will change as the dielectric between them changes due to changing levels |
|
|
What type of level indicator is Capacitance level detection? |
Both point and continuous level detection |
|
|
What are advantages to using a float switch? |
-simple and effective point indication -minimal maintenance -Simple to install |
|
|
What affects the quality of level indicators? |
-Dust -steam -Pressure -temperature -The composition of gases above the reflecting surface |
|
|
What are advantages to using a bubbler as a level indicator? |
-No need to tap the tank -Process fluid does not have contact with the sensor |
|
|
What is a disadvantage of using a bubbler as a level indicator? |
Affected by S.G |
|
|
What's an advantage of using a buoyancy level indicator? |
Being unaffected by pressure |
|
|
What's a disadvantage of using a buoyancy level indicator? |
Affected by specific gravity |
|
|
What are some advantages to using a capacitance level indicator? |
-Simple and rugged -Insensitive to build up |
|
|
What are some advantages to using a conductive level indicator? |
-Good with aggressive liquids -Unaffected by pressure changes |
|
|
What are some disadvantages to using a capacitance level indicator? |
-Can be affected by condensation -RH of bulk solids -Not suitable with semi-conductive fluids |
|
|
What are some disadvantages to using a conductive level indicator? |
-Point detection only -Minimum conductivity of fluid required |
|
|
What are some advantages to using a gauge glass as a level indicator? |
-Simple -Inexpensive |
|
|
What are some disadvantages to using a gauge glass level indicator? |
-Dirt build up -Clear liquids are hard to see -No re-transmission of information |
|
|
What does LAH stand for? |
Level alarm high |
|
|
What are some advantages to using a gauging rod? |
-Simple -Very inexpensive |
|
|
What are some disadvantages to using a gauging rod? |
-Manuel system -Not practical for engineering applications -Requires manpower |
|
|
What are some advantages to using a float method? |
-Relatively simple -suitable for various products -Very accurate |
|
|
What are some disadvantages to using a float method? |
Requires a certain amount of liquid especially in pressure vessels |
|
|
What are some examples of level indication? |
-Float -Displacer -Gauging rod/dip stick -gauge glass/ sight glass |
|
|
What are some advantages to point level control of level? |
-On/Off switches -limit level detection |
|
|
What are some advantages to radiometric level detection? |
-Suitable for a variety of products -mounted on the outside of the tank |
|
|
What are some disadvantages to radiometric level detection? |
-Expensive -Special safety measures are required for gamma system |
|
|
What are some examples of continous level measurement? |
-Hydrostatic -Buoyancy -Capacitance -Microwave -Radiometric -Ultrasonic -Strain gauge |
|
|
What are some advantages to ultrasonic vibration as a level indicator? |
-Non contact -Suitable for solids and liquids |
|
|
What are some disadvantages to ultrasonic vibration as a level indicator? |
-Product cannot product too much foam or be sound absorbent -Not suitable for high pressure/ vaccum |
|
|
What are some advantages to rotation suppression? |
-Simple -Requires no adjustments |
|
|
What are some disadvantages to rotation suppression as a level indicator? |
-Subject to wear -No suitable light for very dense products |
|
|
What are some advantages to vibration dampening as a level indicator? |
-Universal application -No adjustments required -Relatively inexpensive |
|
|
What are some disadvantages to vibration dampening as a level indicator? |
Not suitable for suspended solids <10mm because particles can be trapped between the lines |
|
|
What are some advantages to using a pressure vented level indicator? |
-it's simple -Easy Installation |
|
|
What are some disadvantages to using a pressure level indicator? |
-Is affected by specific gravity -Is affected by the transmitter position -Can't used on a pressurized system |
|
|
What are some advantages to using a pressure dry leg as a level indicator? |
-Unaffected by pressure changes or transmitter position |
|
|
What are some disadvantages to using a pressure dry leg as a level indicator? |
-Is affected by specific gravity -Not suitable with condensable gases |
|
|
When does a thermocouple form? |
When two disimilar metals join together to form a junction |
|
|
How do you complete a thermocouple circuit? |
By joining the two disimilar ends to form another junction |
|
|
How does current flow in a thermocouple? |
By the junctions being at two different temperatures |
|
|
Why is a thermocouple only useful over a certain range of temperature? |
Because of the non-linear shape of the curve |
|
|
What type of thermocouple is only used for lower range temperatures? |
Copper/Constantan |
|
|
What type of thermocouple is used for higher temperature ranges? |
Platinum-rhobidum |
|
|
What are difference thermocouples? |
A pair of thermocouples connected together to measure the temperature difference between two objects |
|
|
What's a thermophile? |
An electrical thermometer consisting of several thermocouples in series to provide a higher voltage output |
|
|
What can a thermophile be used for? |
To measure extremely small temperature differences. |
|
|
What are thermowells used for? |
To protect thermocouples from harsh and corrosive enviroments |
|
|
What are some drawbacks to using thermowells? |
The long response time |
|
|
What is latent heat? |
The heat that is added but doesn't change the temperature |
|
|
What are the three most commonly used sensors for temperature measurements? |
thermocouples, RTDs and thermistors. |
|
|
What are some pros to using RTD's? |
Very rugged, and accurate |
|
|
What are some pros to using thermocouples? |
Wide range, fast response, passive, inexpensive |
|
|
What are some pros to using thermistors? |
Very repeatable, fine resolution, low current, fast response |
|
|
What are some cons to using thermistors? |
They require excitation, have a narrow range, and are non-linear |
|
|
What are some cons to using thermocouples? |
They're only linear in certain regions |
|
|
What are some cons to using RTS's? |
They have a slow response time, require excitation, lead resistance, and are linear. |
