Ultrasonic flowmeter in line
This sensor can be used to measure continuous flow with high accuracy, without the need for change and maintenance and maximum independence from the Reynolds number and other process conditions. Measuring equipment is permanently installed in the pipeline.
Design arrangements based on Apimpms 5 standard:
To design the flow meter, the maximum and minimum flow rates of temperature and pressure must be considered. In addition, the physical properties of the fluid must be considered as expensive on the relative density of vapor pressure and corrosion. The performance of the flowmeter in the linear range of ultrasonic equipment is optimal.
To accurately measure the flow, it is necessary to install thermometers and pressure gauges and equip a density detector. The best place for them is right next to the flow meter and downstream.
Ultrasonic flowmeters generally do not need to use a filter due to the lack of a moving part and not being affected by fluid occupations. Strainers may be used to use flow meters against the effects of equipment such as pumps.
If there is air or steam inside the fluid, the eliminator should be used to remove it. It must be ensured that the flowmeter is recorded in a place where the pipe is always filled with liquid. For this purpose, you can refer to the appropriate arrangements for installation.
The pressure at which the flowmeter operates must be sufficiently higher than the vapor pressure. The following equation may be used to calculate the pressure behind the equipment. To calculate the amount of pressure drop caused by the sensor can be done as the method mentioned in the magnetic flow meter and according to the manufacturer’s catalogs.
where in :
Pb = minimum back pressure of the equipment
p∆ = pressure drop on the flowmeter
P e = equilibrium vapor pressure
Ultrasonic flowmeter installation:
Correct measurement occurs when the pipeline is full of fluid. The formation and aggregation of air strands or gas bubbles in the measuring duct is effective in increasing the measurement error, especially in the flowmeter type of passing time. Therefore, the installation of flow meters should be avoided in the following situations:
- The highest point of the pipeline due to the risk of air accumulation there
- Directly upstream of the free outlet of the pipe in the passage
The use of a tube limiter or perforated plates with a logic surface smaller than the nominal diameter of the tube can prevent the tube from emptying during the measurement.
Execution of input and output in the clamp model:
If possible, the sensor should be installed somewhere other than assemblies such as valves, T-shaped parts and elbows. If there are several obstacles in the path, the highest input and output performance should be considered. It is recommended to meet the following requirements to implement the inlet and outlet of the pipeline in order to achieve accurate measurements.
Run input and output based on Endress + Hauser:
If possible, the sensor should be installed in a place other than assemblies such as valves, T-shaped parts and elbows. If there are several obstacles in the way, the highest input and output performance should be considered. According to the standard, the direct length of the pipe upstream of the flow meter should be 10 times its diameter or more, taking into account the flow attenuator. If no sedative is used, this amount increases to 20 times the diameter of the pipe. Downstream, this value is enough to 5 times the diameter of the pipe. If the manufacturer has specified a specific method and size, he must act accordingly. It is recommended to meet the following requirements for the implementation of pipe inlet and outlet in order to achieve accurate measurements for the company’s equipment.
Advantages and disadvantages of ultrasonic flowmeter are:
- Suitable for large diameter pipes
- No obstruction without pressure drop
- No long life animated player
- quick answer
- Can be installed on an existing system
- They are not affected by fluid properties.
- Its accuracy depends on the fluid flow
- The fluid should be clear relative to the sound
- Clogging occurs in the error tube
- Only possible for limited applications
- The pipeline must be fluid-filled
Turbulence or even torsion of process fluid can affect ultrasonic signals. In common applications, the flow needs to be stable to achieve good fluid measurement, and generally a sufficient amount of straight pipe upstream and downstream allows this. The direct distribution of the pipe should be 10 to 20 times the diameter of the pipe upstream and 5 times its diameter downstream.
The ultrasonic signals in the flowmeter of the passage time type must pass through the width of the fluid in the tube so the liquid must be free of solids and air bubbles. Anything with a different density than the process fluid can affect the ultrasonic signal.
Ultrasonic flowmeter summary:
Most ultrasonic flow meters are installed outside the tube and therefore work without contact with the fluid. This type of equipment, in addition to not being a barrier to fluid flow, is not affected by wear and expensive corrosion. Most ultrasonic flowmeters are two-way and detect fluid flow in both directions.
Doppler flowmeters are not very accurate and do not have high performance, but they provide a non-expensive form of flow monitoring. Independent of the acoustic characteristics, ultrasonic flowmeters are dependent on the flow rate of the fluid and are affected by changes in temperature and density.