A vortex flowmeter is a common industrial flow measurement instrument used to measure the flow of various media, including liquids, gases, and steam. How should a vortex flowmeter be selected? The following are some selection recommendations:
1. Measured Media
Vortex flowmeters are generally suitable for media such as gases, liquids, and steam. However, the following media are not suitable for vortex flowmeter measurement:
1. Fluids containing a large number of solid particles or suspended matter;
2. Media with excessive kinematic viscosity under operating conditions, such as some high-viscosity oils (e.g., heavy oil).
3. When specifying the measured medium, if the medium is steam, indicate whether it is saturated steam or superheated steam.
2. Flow Range
1. The normal flow rate should be controlled within the upper-middle range of the vortex flowmeter's measurable range. Since measurements of the lower limit flow rate of a vortex flowmeter are easily affected by pipeline vibration, measurements at the lower limit should be avoided as much as possible. 2. When the flow range exceeds the measurable range of a vortex flowmeter, a reduction or expansion method can be used, but the following should be noted:
- The instrument's reduction or expansion should not be too large. Reduction increases the flow velocity, increasing resistance and backpressure, while expansion is more likely to cause cavitation.
- If a straight pipe section is available, a "reducer + straight pipe section" combination should be selected to ensure stable flow measurement.
- The flow range selection should also consider whether the Reynolds number is within the normal range.
3. Vortex flowmeters are not suitable for measuring pulsating flows: Powerful mechanical equipment such as Roots blowers and reciprocating pumps in the piping system will generate strong pulsation. If the pulsation frequency is within the vortex frequency band, measurement errors will occur. Severe pulsation may even prevent the formation of a Karman vortex.
III. Pipe Diameter
Vortex flowmeters can be installed in-line or in-line, depending on the installation method.
1. For in-line flowmeters, the pipe diameter is the same as most other flowmeters, with a minimum diameter of DN15 and a maximum diameter of DN300. 2. If a larger diameter is required, an insert-type installation can be selected. The standard diameter range is up to DN2000, and diameters above DN2000 are available upon agreement.
IV. Measurement Accuracy
Vortex flowmeters have several levels of accuracy, each categorized by the medium being measured.
1. For pipeline-type vortex flowmeters, the measurement accuracy can reach Class 1.0 for liquids and Class 1.5 for gases.
2. For insert-type vortex flowmeters, the accuracy can reach Class 1.5 and Class 2.5.
V. Medium Temperature
Generally speaking, there are three temperature ranges: ambient, medium, and high.
1. The temperature ranges are -40°C to 100°C (ambient), 100°C to 250°C (medium), and 100°C to 320°C (high).
2. If the medium temperature on site is higher, such as superheated steam, an orifice plate flowmeter can be used for measurement. VI. Nominal Pressure
Primarily categorized by installation method, the market primarily demands the following types:
Flange-mounted (2.5MPa), flange-connected (1.0/1.6/2.5MPa), and plug-in (1.6MPa/2.5MPa/4.0MPa).
VII. Installation Environment
The vortex signal output method is selected based on the intended use of the vortex flowmeter. There are several main options:
1. When the measured medium is a compressible fluid and the temperature and pressure of the medium on-site fluctuate significantly, it is recommended to use a vortex sensor with remote pulse signal transmission, along with a flow integrator, pressure transmitter, and temperature transmitter with temperature and pressure compensation.
2. When the flowmeter is installed indoors in a relatively good environment and remote signal transmission is not required, only flow readings are required on-site. Furthermore, if the flowmeter is installed in a convenient location for operation and data reading, it is recommended that users choose a digital vortex flowmeter.
3. When the flowmeter's installation environment is poor, the installation location is inconvenient for on-site flow reading, or when centralized management is required, it is recommended to use a pulse output sensor with a flow totalizer or a vortex transmitter with a 4-20mA standard current output.
4. When on-site flow measurement and remote signal transmission are required, a digital vortex transmitter with a 4-20mA output is recommended.
5. When on-site flow reading is not required and only standard signal transmission is required, a vortex transmitter with a 4-20mA standard current output is recommended.
VIII. Protection Ratings
Common IP ratings for vortex sensors include IP65, IP67, and IP68.
1. IP65 represents protection against dust intrusion and water jets;
2. IP67 represents protection against dust intrusion and temporary submersion;
3. IP68 represents protection against dust intrusion and continuous submersion. In general, the appropriate IP rating should be selected based on the vortex flowmeter's installation location:
- For indoor installations, IP65 is sufficient;
- For outdoor installations above ground level, select an IP rating of IP65 or higher;
- For installations below ground level in a ditch, select IP68 and a separate amplifier to prevent damage from rainwater soaking.
- For flammable and explosive environments, an explosion-proof vortex flowmeter should be used.