In industries where knowing the flow or flow of a fluid is critical to maintaining the quality of a product, the use of flow meters and controllers is essential. The most simple and effective: The orifice plate.
What is a hole plate?
The orifice plate is a device that allows measuring the flow of a fluid that passes through a pipe. It consists of a disk with a hole in the center of it that is placed perpendicular to the pipe.
It is a primary measuring element, but it is widely used due to its ease of use, low price, low maintenance, and high efficiency.
Types of hole plates
There are four types of hole plates according to the desired application.
- Concentric orifice plates: In these plates, the orifice of the disc is in the center of it. Universal application for clean fluids.
- Conical concentric orifice plates: In this case the orifice, as well as the concentric plates, is in the center of the disc, but in this, the diameter of the orifice is reduced as the fluid passes through the disc. It is used for fluids that have a high Reynolds number, that is fluids that tend to behave turbulently.
- Eccentric hole plates: Are those in which the hole is not in the center of the disk but slightly down. It is used for small diameter pipes.
- Segmented concentric orifice plates: Here the difference with the other concentric plates is that the orifice is not a circle but is segmented, forming a semicircle. It is used to measure fluids that contain particles.
How does a hole plate work?
The operation of an orifice plate is based on the Venturi effect. This consists of a phenomenon that reduces the pressure of a fluid that crosses a pipe, and this increases its speed due to a decrease in the diameter of the pipe.
Therefore, to measure the flow of the fluid, two shots are placed one before the plate and the other after, which capture the differential pressure that is generated due to the increase in speed. Then, through Bernoulli’s principle, the pressure difference is proportional to the square of the flow rate.
Applications of a hole plate
Being a flow measurement element, the orifice plate has thousands of applications and most are industrial.
- Chemical industries
- Water and gas treatment and distribution
- Beverage industries
- In productive processes where it is necessary to know the flow rate of a fluid
Parts of a hole plate
- A solid disk
- A hole in the disk through which the fluid is passed.
Features of a hole plate
- It can withstand temperatures up to 800ºC
- Can work with fluids at pressures up to 400 Bar
- It has an accuracy of 0.5% of the flow measurement
Difference between hole plate and Venturi tube
The Venturi tube and the orifice plate are both used for flow measurement. They change only the operation they use to achieve this measurement. The difference of the Venturi tube with the orifice plate is that the decrease in the section of the tube is made directly by the same tube.
In other words, the Venturi tube is a special tube that has a decrease in the section at one point while the orifice plate is what is placed in a common tube to know the flow of the fluid that passes through it.