What’s an Orifice plate flow meter？
The orifice flow meter is a differential pressure flowmeter. It is the most widely used flowmeter. We combine the standard orifice plate with a multi-parameter differential pressure transmitter (or differential pressure transmitter, temperature transmitter, and pressure transmitter) to form a differential pressure flow device with a high range ratio. You can use it to measure the flow of gas, steam, liquid.
The throttling device is also known as a differential pressure flow meter. It comprises a primary detection device (throttle) and a secondary device (differential pressure transmitter and flow indicator). You can use it in the flow measurement of gases, steam, and liquids. It is simple in construction, easy to maintain and stable in performance.
The fluid that fills the pipe flows through a throttling device inside the tube. It causes a local constriction near the throttle, which increases the flow rate. It creates a static pressure difference between its upstream and downstream sides.
You can use the orifice plate flow meter for process control and measurement in petroleum, chemical, metallurgy, electric power, heating, water supply, and other fields.
What are the types of orifice flowmeters?
The development of orifice flowmeters has a long history. Nowadays, it is one of the most used flow meter types in flow measurement. There are six types of orifice flow meters that we commonly use today. They are standard orifice plate flowmeter, ring orifice plate flowmeter, round lack of orifice plate flowmeter, wear-resistant orifice plate flowmeter, eccentric orifice plate flowmeter, and limited flow orifice plate flowmeter. These types of flowmeters are often used in industrial production. They are also available in large quantities. They have the features of stable function, accurate measurement, long service life, and large range ratio. They can also measure liquids, gases, steam, and other media. Therefore, they are widely used in petroleum, chemical, metallurgy, light industry, coal mining, and other industrial sectors.
The orifice plate flow meter is a device for measuring the flow of fluids in pipes. We can use it to measure the flow rate of various media such as gases and liquids. Nowadays, to meet the needs of different industries, there are also many kinds of orifice plate flowmeters on the market. The different types of orifice plates also have other functions.
How to distinguish between these types of orifice plate flowmeters?
Standard orifice plate flowmeter
The standard orifice plate flow meter is a high-range ratio differential pressure flow device consisting of a standard orifice plate and a multi-reference differential pressure transmitter (or differential pressure transmitter integrated with an orifice plate flowmeter temperature transmitter and pressure transmitter). We can use it to measure the flow of gas, steam, liquid, and natural gas.
The standard orifice flowmeter is stable and reliable, and long service life. It has a low price and is commonly used in industry to measure the flow rate of the exterior. It is fully machined and uses international standards. It is subjected to a serious calibration check. The user can use it with confidence after purchase. We use the flowmeter in a wide range of applications. We can measure all single-phase flow rates and measure some mixed-phase flows with this flowmeter. This orifice plate flowmeter can be used without actual flow calibration.
However, it has some minor drawbacks. It is not very accurate, and its accuracy is medium in flow meters. It is because it is susceptible to the influence of many factors, making it difficult to improve the accuracy.
It is also more prone to fouling and abrasion when applied. It can lead to a change in the coefficient of media flow. It can lead to certain measurement errors. Therefore, to reduce the measurement error, we need to improve the edge wear of the throttle and clean it regularly.
Circular orifice plate flowmeter
The open hole of the circular notched orifice plate flow meter is a part of a circle (circular notched part). The diameter of this circle is 98% of the diameter of the pipe. The center of the circular part of the opening should be precisely positioned to be concentric with the line. It ensures that the tube and the gaskets do not cover the opening at the ends or due to the eccentricity of the pipe. The circular shortage orifice flowmeter is suitable for measuring dirty media such as wet gas. It can avoid the dirt in the orifice plate before and after the siltation. Therefore, it is widely used to measure all kinds of gas and dirty fluids.
The orifice plate flow meter is suitable for measuring full steam, compressed air, gas, furnace exhaust gas, cooling water, condensate, corrosive chemical solutions, and fluid media. It does not require long straight pipe sections. It can also be operated in harsh pipeline conditions. It is suitable for the measurement of dirty and corrosive fluids. It is highly accurate and has good reliability.
However, the circular orifice flow meter is only suitable for horizontal or inclined pipes installation. Therefore, we cannot use it on vertical pipes.
Wear-resistant orifice flow meter
The wear-resistant orifice plate flowmeter has excellent abrasion resistance, so there is no sharp edge abrasion. It can be designed for in-line pressurized installation and in-line pressurized maintenance. It can be adapted to dirty media such as gas. The pressure relief tube can be withdrawn for maintenance in-line. The throttle device is integrated into the differential pressure transmitter and the pressure and temperature transmitter. It saves installation and maintenance work and costs. It is highly adaptable, with primary components of the same construction. It is suitable for all conventional media except for hygienic and highly corrosive requirements. In addition, it has a relatively stable measurement performance and high accuracy.
Ring orifice plate flowmeter
The annular orifice plate is suitable for fluid (gas, steam, liquid) media. It is an economical flow sensor developed based on the standard orifice plate. Because it uses the annular channel structure, the measurement of various dirty media in the orifice plate and the pipe between the annular gap can easily pass. Thus the ring orifice flowmeter can be widely used in the flow measurement of dirty media. It is connected by flange or welding.
The annular orifice plate throttling device is the same as the standard orifice plate. It is based on the basic principles of the fluid continuity equation and Bernoulli’s equation. We install the annular orifice plate in a circular tube, and when the liquid flows through the throttling device, a pressure difference is created between its upstream and downstream sides.
It can measure liquids or gases that are rich in solid particles. It can also operate in harsh piping conditions. It is suitable for measuring plentiful steam, compressed air, gas, furnace exhaust gas, cooling water, condensate, various corrosive chemical solutions, and various fluid media.
The annular orifice plate flowmeter works more reliably than the circular orifice plate and eccentric orifice plate. It is more accurate in its measurement. It is more easily adapted to the flow measurement of high-temperature and high-pressure fluids. It can also be made into a corrosion-resistant type at a lower cost, thus measuring the flow of corrosive liquids.
It automatically resolves upstream flow disturbances and effectively avoids the flow meter’s non-axisymmetric distribution. So there is no need to worry about contamination of the throttle.
Eccentric orifice flowmeter
The opening of the eccentric orifice plate flowmeter is part of the circle. The eccentric orifice plate flow meter is a throttling flow sensor developed based on the standard orifice plate. It uses a circular channel structure so that a variety of dirty media through the orifice plate and the pipe between the ring between the slit easily through. Therefore the eccentric orifice plate flow meter is widely used for flow measurement of dirty media. It can avoid the dirt in the orifice plate before and after the siltation. The eccentric orifice plate is suitable for measuring wet steam, flue gas, coke oven gas, and other media. To improve the accuracy of the eccentric orifice plate, we can use a straight section or flange connection above and below the straight pipe section structure form.
The eccentric orifice plate is only suitable for horizontal or inclined pipelines installation. It cannot be used on vertical pipes. If the fluid to be measured contains solid particles, the notch should be below. If there is gas in the liquid, we should place the notch above.
Limiting orifice flowmeters
The limiting orifice plate is a throttling element. The limiting orifice plate can reduce the pressure and limit the flow of the fluid conveying process. It has the advantages of simple structure, easy processing, low manufacturing cost, easy installation, etc. Under the premise of meeting the process requirements, we use the restriction orifice plate instead of regulating valve to limit the flow or reduce the pressure. Therefore, it will greatly reduce the investment and operation and maintenance costs. Consequently, it has been widely used in process installations abroad. It plays an essential role in the safe operation of the plant.
The limiting orifice flowmeter can be used as a flow measurement element and a throttling element to limit the flow and reduce pressure. When there is a pressure difference between the front and rear of the orifice plate, the fluid flows through the orifice plate. The flow rate through the orifice plate increases for a certain aperture as the pressure difference increases. However, when the differential pressure exceeds a specific value (known as the critical pressure difference), the flow rate of fluid through the orifice plate will reach the speed of sound (not all media flow through the restricted orifice plate flow rate reaches the speed of sound). For gases through the orifice plate limit speed is the speed of sound. However, the principle of the restriction orifice flowmeter is that, given the differential pressure and orifice diameter before and after the orifice plate, there is an upper limit to the flow rate of either liquid or gas through the orifice plate. Therefore, no matter how the differential pressure increases, as long as the pressure upstream of the orifice plate maintains a certain, the flow through the orifice plate will remain at a specific value and no longer increase. The flow restriction orifice flowmeter is based on this principle to limit fluid flow and reduce pressure.
Flow restriction orifice flowmeter is divided into single orifice plate and multi-hole plate according to the number of openings on the orifice plate. And it can be divided into single-stage and multi-stage according to the number of orifice plates.
A restricted flow orifice plate flowmeter can be used for process materials needed to reduce the pressure of the occasion.