Question

Flow measurement (rotameter)

1. If a rotameter is not level, is the reading it provides too high or too low? Why?

2. Why is it important to submerge the tubing end before taking the initial rotameter reading?

3. What is one disadvantage of a rotameter?

4. What should you do periodically to maintain the accuracy of a rotameter.

Answer 1

1. Actually, it can go either way. The reading would be too high since the gravity effect on the bob would be less and buoyancy force and drag force will dominate.

In another case, if there is friction acting on the bob then it may also give too low reading. But this case can be neglected because we assume the devices ideal (with no friction).

2.It is important to submerge the tubing end before because it allows us to calibrate the rotameter before taking measurements.

3. The major disadvantage is that rotameter should be placed vertically because gravity plays an important role here.

4. a.Always try to keep bob clean to avoid any friction.

b. Use flow conditioners to avoid flow disturbances and accurate readings.

c. Maintain constant temperature during the reading.

d. Keep the rotameter always vertically.