Features of Orifice plates
Design Pressure: No limitation. Limited by DP transmitter
Design Temperature: No limitation. Limited by DP transmitter
Sizes: Maximum size is pipe size
Flow range: limited only by pipe size.
Fluids/ Applications: Cryogenic / clean gases & liquids/ Steam (saturated/superheated)
MOC: No limitation (Steel/Monel/nickel/ haste alloy)
Accuracy: It varies from ±0.25% to ±0. 5% of actual flow. The accuracy of DP transmitter varies from ±0.1% to ±0. 3% of full scale error.
Rangeability is 3:1 to 5:1.
Upstream length/ Downstream straight length is 20 / 5
Advantages of Orifice plates
Easily installed between flanges.
Fabrication simple and inexpensive.
No limitations on the materials of construction, line size and flow rate
Cost relatively independent of pipe diameter since cost of DPT is fixed.
No process interruption for exchange of DP transmitter.
Disadvantages of Orifice plates
High permanent pressure loss & hence high energy consumption to overcome pressure loss.
Impractical for systems with low static pressure.
Measuring range to about 3:1 to 5:1.
Accuracies decrease with Beta ratios above approximately 0.7.
Subject to damage by water hammer and foreign objects.