What is the accuracy of an orifice plate flow meter?
The accuracy of an orifice plate differential pressure flowmeter that is fabricated and installed per applicable standards can be on the order of 0.60 percent of rate.
What is bore diameter in orifice plate?
The orifice plate has a typical bore diameter that ranges from 30% to 75% of the inside diameter of the pipe work in which it is installed. A beta ratio of 0.4 signifies that the orifice bore diameter is 40% of the pipe inside diameter.
How is orifice bore diameter calculated?
Divide the flow of the liquid by the velocity of the liquid to determine the area of the orifice in square feet. In the above example, you would divide 8 by 2. The total area of the orifice would be 4 square feet.
How thick should an orifice plate be?
The thickness ‘E’ of the plate shall be between ‘e’ and 0.05 D. However, when 50 mm ≤ D ≤ 64 mm, a thickness ‘E’ up to 3.2 mm is acceptable.
Does orifice size affect flow rate?
A reduction in orifice size results in decreased flow as only so much liquid can pass through the orifice. In all of the above cases, the inlet pressure is constant and the outlet pressure is, effectively, zero (atmospheric) as there is nothing to restrict flow on the exit side of the orifice.
How do you inspect an orifice plate?
Check whether the inside diameter of the orifice plate bore matches the size stamped on the plate using a calibrated micrometre. Ensure the bore edges are free of any gouges or nicks. Also, ensure the edge of the plate is sharp by running your fingernail across it.
Is standard for orifice plate?
The relevant standards are BS 1042 and the equivalent ISO 5167. One of the principle advantages of orifice plates manufactured and installed following these standards is that they do not require calibration. This means that orifice plates are very cost effective on larger line sizes.
How do I choose an orifice plate?
Design Considerations of Orifice Plate
- Square Root Relationship.
- Density.
- Beta (β) Ratio. β ratio < 0.2 Means: β ratio > 0.7 Means:
- Reynolds Number.
- Selection of Differential Pressure Transmitter Range.
- Location of Pressure Taps. Flange Taps: Venacontractra & Radius Taps: Corner Taps:
- Installation.
Do orifice plates reduce flow?
In flow control applications, orifice plates are used as restriction devices to regulate fluid flow or reduce the flowing pressure downstream of the orifice plate. The use of a fixed restriction orifice can be beneficial and economic by reducing the demands on other flow system components.
What is orifice coefficient?
The coefficient of discharge for orifices in pipes varies from 0.60 to 0.80 and varies with the diameter ratio. For flow nozzles in pipelines, the coefficient varies from 0.96 to 1.2 for turbulent flow and varies with the diameter ratio.
How does orifice size affect flow rate?
Why bevel is used in orifice plate?
A beveled orifice should form an angle of::
The orifice plate inserted in the line causes an increase in flow velocity and a corresponding decrease in pressure. The flow pattern shows an effective decrease in the cross section beyond the orifice plate, with a maximum velocity and minimum pressure at the vena contracta.
What are the disadvantages of orifice plate?
Disadvantages
- Relatively high permanent pressure drop.
- Their characteristic may change due to erosion and corrosion.
- It may cause clogs in slurries. Not good with fluid having high viscosity.
- The fluid must be in single phase and homogeneous.
- Square root characteristics.
How is orifice plate calculated?
To calculate the flow rate of fluid passing through an orifice: Multiply the gravitational constant g with the mean centerline H . Multiply the produce with 2 . Find the square root of the product.
What happens if the edge of the orifice is square?
Square-edged Orifice Plates
The purpose of having a square edge on the hole in an orifice plate is to minimize contact with the fast-moving moving fluid stream going through the hole. Ideally, this edge will be knife-sharp.
Does orifice plate reduce pressure?
An orifice plate is a device used for measuring flow rate, for reducing pressure or for restricting flow (in the latter two cases it is often called a restriction plate ).
Which is better Venturi or orifice?
The pressure loss in venturi meter is 10% while in the orifice meter the pressure loss is 50-60%. The coefficient of discharge in the venturi meter is 0.98 while in orifice meter it is 0.6. The turn down ratio of venturi meter is 10:1 while in orifice meter it is 5:1.
How do orifice plates reduce pressure?
The typical orifice plate has a concentric, sharp-edged opening. Because of the smaller area, the fluid velocity increases to cause a corresponding decrease in pressure. The flow rate can be calculated from the measured pressure drop across the orifice plate.
How is orifice DP calculated?
To estimate the orifice flow rate:
- Insert the diameter of the orifice, d = 50 mm .
- The calculator will now estimate the area of orifice, A .
- Enter the coefficient of discharge, Cd = 0.8 .
- Enter the value of the mean center line, H = 200 mm .
- The acceleration due to gravity, g is filled in as 9.81 m/s2 .
How does orifice size affect pressure?
The orifice size of the nozzle determines the operating pressure of your machine. As a rule of thumb, the smaller the orifice, the greater the restriction of water flowing through the machine. This causes the pressure to increase. Choosing a nozzle with too large of an orifice will reduce operating pressure.
What is the disadvantage of orifice plate?
Disadvantages of orifice meter:
It requires the flow of axial velocity vectors. It causes a pressure drop in the fluid. Its accuracy is affected by the density, pressure and viscosity of the fluid. The range of measurement of viscosity limits of fluids.
Why head loss is more in orifice meter?
In the venturi meter, there is a gradual contraction between the inlet and throat because of that the head loss is less in the case of the venturi meter. In the orifice meter there is a sudden contraction of the area between inlet and throat because of that there is more loss of head in the case of the orifice meter.
Does an orifice plate reduce flow?
Which is the main disadvantage of orifice meter?