Level and Density Measurement Objective Questions
1. An open tank contains a liquid of varying density and the level within the tank must be accurately measured. The best choice of measurements system would be:
a. Bubble tube
b. Diaphragm box
c. Float and cable
d. Head type with differential pressure transmitter
Answer: c
2. A chain-suspended diaphragm box and pressure instrument are used to measure liquid level in a tank which is 10 feet in diameter and 15 feet deep. The tank contains a liquid that has a specific gravity of 0.9 at ambient temperature. The span of the pressure instrument required is approximate
a. 10 psi
b. 25 psi
c. 5 psi
d. 15 psi
Answer: c
3. A pressurized tank contains a líquid, SG = 1.0, and the level measuring pressure taps are 100 inches apart. A pneumatic differential pressure transmitter is used to measure level. The leg that connects the top of the tank to the transmitter is filled with tank líquid. The top tap should be connected to:
a. The low-pressure tap on the transmitter.
b. The high-pressure tap on the transmitter.
c. Either the high- or the low-pressure tap.
d. The high-pressure tap but through a seal chamber
Answer: a
4. In Question 3, the bottom connection is made to the low-pressure tap on the transmitter and the top is made to the high-pressure tap. The signal output, if the transmitter is calibrated 0 to 100 inches, when the tank is full will be:
a. Top scale value
b. Bottom scale value
c. 0
d. A measure of density
Answer: b
5. A plant has a water tower mounted on top of an 80-foot platform. The tank is 30 feet high. What is the height of water in the tank if a pressure gauge on the second floor, height 15 feet, reads 40 psi.
a. Full
b. 12.42 feet
c. 4.74 feet
d. 27.42 feet
Answer: d
6. A displacer is 5 inches in diameter and 30 inches long. If it is submerged to a depth of 20 inches in líquid sa = 0.8, what force will it exert on the top works?
a. 11.3 pound
b. 426.3 pounds
c. 35.5 pounds
d. 1.47 pounds
Answer: a
7. A closed tank level (Sa = 0.83) is measured with a differential pressure transmitter.The level may vary from 10 to 100 inches.The high-pressure tap is 10 inches above the transmitter and a water seal fluid is used. A pressure repeater is used for the top tank pressure. The differential pressure transmitter should be calibrated
a. 10 to 100 inches
b. 10 to 84.7 inches
c. 8.3 to 74.7 inches
d. 8.3 to 98.3 inches
Answer: b
8. To resist the corrosive effects of a very unusual, highly explosive chemical, a storaget ank is lead-lined.L evel measuremenist difficult because the material also solid if lies once it enter a measuring tap. To measure the level with accuracy the best choice would be:
a. Weigh the tank and its contents and zero out the tare weight of the tank.
b. Use a radioactive level measurement.
c. Install a conductivity level measurement.
d. Use a thermal conductivity level detector
Answer: a
9. A displacer 48 inches long and 1% inches in diameter is used to measure density on a 4 to 20 mA dc transmitter.Its total submerged weights hanges from 1.42 pounds to 5.7 pounds. If the density is checked and determined to be 0.4 when the output is 4 mA dc, the density at an output of 12 mA dc is:
a. 0.6
b. 0.8
c. 1.0
d. 1.6
Answer: c
10. A density measuring system is set up as shown in Figure. The H distance is 100 inches and the lower transmitter is calibrated to a 120-inch span. If the transmitter is pneumatic and delivering a 12-psi signal, the specific gravity of the tank’s contents is:
Fig : In an open or closed tank with varying level and/or pressure where seal fluid or purge is not suitable, a pressure repeater can be used.
a. 1.0
b. 0.83
c. 0.9
d. 1.2
Answer: c