Introduction
Steel Blow-off induced Vortex-shedding Flowmeter is a flow measurement method which has been widely used in steel mills and other industrial plants. It uses the Bernoulli equation and the principle of a cavity to measure the volumetric flowrate through a pipe. This method is particularly appealing because it is simple and accurate, requiring little maintenance or calibration.
Background Information
The Steel Blow-off induced Vortex-shedding Flowmeter is based on the principle of fluid flow in pipes and the Bernoulli equation. The Bernoulli equation is an equation defining the static and dynamic pressures in a system with viscous flow, which involves the parameters of density, velocity and pressure of the fluid, as well as energy per unit mass of the flow. The pressure of the flowing fluid is decreased as the velocity increases. This decrease in pressure creates a negative pressure area in the tube, with the pressure gradient being proportional to the velocity of the fluid. This pressure decrease is known as the pressure difference, which causes the formation of a cavity behind the leading edge.
Description
The Steel Blow-off induced Vortex-shedding Flowmeter works by using the Bernoulli equation and the principle of a cavity. The cavity is created by the blowing of air from the inner wall of the pipe at a predetermined rate. As the air enters the pipe, the air causes a stir in the fluid, which causes the fluid flow to increase. This increase in fluid flow causes a decrease in pressure, which in turn causes the formation of a cavity in the pipe. This cavity is then used to measure the volumetric flowrate of the fluid.
The measurement is accomplished by taking the difference between the static pressure before the cavity and the dynamic pressure after the cavity. The static pressure is measured by a pressure sensor before the cavity, and the dynamic pressure is measured by a pressure sensor at the end of the cavity. This difference in pressure is then used to calculate the volumetric flowrate.
Advantages
The Steel Blow-off induced Vortex-shedding Flowmeter is a very user-friendly method of flow measurement. It does not require complex instrumentation and can be easily installed in existing pipes, using a wide range of diameters. The method also does not require extensive maintenance, as the cavity is created and maintained by the flow of air. The accuracy of this method is also very high, with typical accuracy levels of +/- 0.5%.
Disadvantages
The major disadvantage of this method is that the air pressure used to create the cavity can be affected by the process conditions, such as the composition of the gas, temperature and pressure. This can lead to errors in the measured flowrate. Additionally, this method is not suitable for measuring the flowrate of slurries or highly viscous fluids, as these can disrupt the formation of the cavity.
Conclusion
The Steel Blow-off induced Vortex-shedding Flowmeter is a widely used method for measuring the volumetric flowrate of gases and liquids in pipes. This method is convenient and economical, requiring few maintenance or calibration steps. It is best suited for measuring low viscosity process gases and liquids, although it may not be suitable for measuring the flowrate of slurries or highly viscous fluids. Despite the potential for errors due to process conditions, this method is a reliable and accurate means of volumetric flowrate measurement.
