Instrumentation Jobs questions flow measurement
What
are the primary elements used for flow measurement?
The primary elements used
for flow measurement are:
·
Orifice
Plate.
·
Venturi tube.
·
Pitot tube.
·
Annubars.
·
Flow Nozzle.
·
Weir & Flumes.
What are the different types of orifice
plates and state their uses?
The different types of
orifice plates are:
·
Concentric.
·
Segmental.
·
Eccentric.
·
Quadrant Edge.
Concentric: (Centered)
The concentric orifice plate is used for ideal liquid as well as gases and steam service. This orifice plate beta ratio falls between of 0.15 to 0.75 for liquids and 0.20 to 0.70 for gases and steam. Best results occur between value of 0.4 and 0.6, beta ratio means ratio of the orifice bore to the internal pipe diameters.
45º beveled edges are often used to minimize
Friction resistance to flowing fluid)
Eccentric:
The eccentric orifice plate has a hole eccentric. Used for measuring containing solids, oil containing water and wet steam. Eccentric plates can use either flange or vena contracta taps, but the tap must be at 180º or 90º to the eccentric opening.
Eccentric orifices have the bore offset from center to
Minimize problems in services of solids-containing
Materials.
Segmental:
The segmental orifice place has the hole in the form segment of a circle. This is used for colloidal and slurry flow measurement. For best accuracy, the tap location should be 180º from the center of tangency.
Segmental orifices provide another version of plates
Used for solids containing materials. Quadrant Edge:
It common use in Europe and are particularly useful for pipe sizes less than 2 inches.
Quadrant edge orifices produce a relatively constant
Coefficient of discharge for services with low
Reynolds numbers in the range from 100,000 down
to 5,000.