Level Measurement Multiple Choice Questions
Question 1
Suppose a storage vessel holds a liquid of unpredictable density. Identify which level measurement technology will not maintain accurate measurement of liquid height in the vessel as the liquid density changes:
(A) Differential pressure transmitter
(B) Guided-wave radar
(C) Ultrasonic
(D) Float and tape
(E) Sightglass
Answer : A
Question 2
The main advantage of a “dip tube” or “bubbler” system for level measurement is that:
(A) It isolates the pressure transmitter from the process fluid
(B) It always elevates and never suppresses the calibration range
(C) It is less expensive to operate than a direct-connected transmitter
(D) It compensates for changes in liquid density
(E) It can measure both solid and liquid levels
Answer : A
Question 3
If the specific gravity of the liquid inside the vessel increases, what aspects of the transmitter’s calibration will we need to change in order to maintain accurate liquid level measurement?
(A) We will need to change the transmitter’s LRV and linearity
(B) We will need to change the transmitter’s linearity and span
(C) We will need to change the transmitter’s LRV and URV
(D) We will need to change the transmitter’s linearity and zero
(E) We will need to change the transmitter from linear to square-root characterization, and adjust the zero
Answer : C
Question 4
A displacer-type level transmitter has a cylindrical displacer 30 inches long and 2.5 inches in diameter. When fully submerged in a petroleum fuel (Gf = 0.82), how much buoyant force will the displacer generate?
(A) 5.320 pounds
(B) 6.488 pounds
(C) 4.363 pounds
(D) 17.45 pounds
(E) 2.792 pounds
Answer : C
Question 5
Calculate the LRV and URV for this ΔP-based liquid level measurement system:
(A) LRV = 0” H2O ; URV = 444” H2O
(B) LRV = 84” H2O ; URV = 444” H2O
(C) LRV = 7” H2O ; URV = 37” H2O
(D) LRV = 444” H2O ; URV = 0” H2O
(E) LRV = 0” H2O ; URV = 360” H2O
Answer : B
Question 6
A d/p cell used to measure liquid level has a “suppressed zero.” This means:
(A) The transmitter is located above the 0% liquid level mark
(B) The transmitter uses filter circuits to suppress noise to a zero level
(C) The liquid is less dense than water
(D) The transmitter is located below the 0% liquid level mark
(E) The elevation of the vessel is below sea level
Answer : D
Question 7
Which of the following level-measurement technologies cannot be adapted to measure solid (powder) level in a vessel?
(A) Displacer
(B) Float and tape
(C) Radar
(D) Ultrasonic
(E) Load cell
Answer : A
Question 8
A guided-wave radar transmitter is able to measure liquid interface levels based on differences of between the two liquids.
(A) Ionization potential
(B) Density
(C) Speed of light
(D) Temperature
(E) Dielectric constant
Answer : E
Question 9
The following liquid level switch will only function with liquids that are .
(A) Electrically conductive
(B) Denser than water
(C) Absolutely pure (i.e. not a solution)
(D) In a state of laminar flow
(E) Optically transparent
Answer : A
Question 10
Calculate the hydrostatic pressure at the bottom of a vessel holding 17 vertical feet of liquid with a density of 55 lb/ft3.
(A) 33.8 PSI
(B) 8.36 PSI
(C) 21.2 PSI
(D) 6.49 PSI
(E) 5.90 PSI
Answer : D
Credits : by Tony R. Kuphaldt
My Answer against Question 1 :
first of all such tank with such type of liquid can be called a Blending type i.e. for example we have Gasoline tank of different Density from reformer unit ,if we want to achieve accurate level measurement using for example Level measurement type (D) and regardless the other types also can be use and whether the others can give accurate level measurement or not and even for my selection (D) ,all types can not first measure the density together with level ,only level with accuracy related to any side effect during filling the tank or evacuate using pumps .
yes, here the level measurement can be changed from type to type,but to measure or sense the density if we have different sections(Unpredictable density ) on the assumption that we have Blending Tank as i mention above or other tanks for Kerosene also receive slop of density approach to Kerosene density and so on for Gas-Oil as well.
So we can measure the density of the blend product by using what so called Density on line meter and can be install together with the level or away from level transmitter but on same line of O/P port of tank and can read the density for each section and we can sense where is the density change for example Gasoline of density (0.71-0.77 kg/L or 719 KG/M3 ) this means different ranges of density or maybe we have slop (mixed product ) its density approach to Gasoline density (by the way slop comes from loading arms for tankers and usually pumped from slop tanks to main tanks products if the chemist after doing chemical test on its density decide to which tank should be pump .the density meter shall have a read unit inside the control room or even outside of Exd type the operator can watch the change in density .
Therefore and In general we do not have a level measurement tool or devise used to measure both Level and density despite the mathematical relationship between (HEIGHT -DENSITY-PRESSURE )
So the most successful measurement for a tank have Unpredictable Density to measure its level or accurate level is to use the above even the last one but for Density we need to install what so called ON Line density meter( 4-20 mA ) Output like On line viscosity meter to viscous liquids ,what is for level should be use and what is for density also should be use there is no common equipment use 2 in 1 i.e. even if we have different section or density no level measurement can sense accurately and read the level during the change of density for each section again despite the relationship between Height /Pressure /Density on mathematical model .
Thank you Mr. George Ibraheem Yokhana, for sharing your knowledge & experience with us.
Mr Reddy : As a matter of fact i worked in North refineries Depot /Baiji refinery -Iraq between 1985-1989 so we have tank farm of 10 tanks each of capacity 27000 M3 for different types of white hydrocarbon product (Naphtha-Gasoline-Kerosene -Gas Oil ) (please note i put here the sequence of products according to program of pumping i.e. if u want to pump all products on same pipe line ,this means u have to start with Naphtha-Gasoline-Kerosene-Gas Oil and vise versa Gas Oil -Kerosene- Gasoline-Naphtha the reason for this is the density of each product and the section or Area between the two products normally called the slop ,which means here the product has no specific density to incline toward specific product i.e. it is not Gasoline nor Naphtha in between for this i mentioned before we can not measure the density once we have Unpredictable Density especially when u are working in Blending
to solve and controls the major problem which is the possibility of CONTAMINATION we used ON LINE DENSITY METER to avoid any contamination especially in Receive the product from main pump house i.e. from refineries to depots or from main depots to another ,for this the on line density meter usually in receiving station installed about 500 Meter away from main entry point this is for Alarm issue if we have contaminated product in order to let the product go to slop tanks not main tanks and avoid contamination(especially if we have loading and non loading arms for Tankers and then for domestic use while in main pump house yes we need density this is also for contamination i.e. not to pump contaminated product to another depots ,so this is the benefits of using On line density meters and are better than use DP transmitter and the most famous manufacturer is Schlumburger (Solartron Brand ) for both Density and Viscosity On,line measurement for any Hydrocarbon product whether it was liquid or Gas ,of curse there are other brands of same rank
Please provide justification against answers which will help to understand & clear the concept.