7F2C Vortex Flowmeter Overview
The 7F2C is a universal multifunctional flowmeter equipped with wet steam detection capability, delivering the highest measurement accuracy. It is particularly suitable for measuring wet steam, saturated steam, superheated steam, gases, and liquids (as well as cryogenic media), and has been optimized for steam measurement to improve accuracy.
The flowmeter features high integration, with built-in temperature and pressure measurement devices for steam and gases, and includes straight pipe section compensation, saving installation space. It is the vortex flowmeter with the best linearity, and its measurement accuracy remains constant when the Reynolds number is not less than Re10000.
Core Advantages and Features
- High Accuracy: Best linearity, measurement accuracy unaffected by Reynolds number (Re≥10000).
- Multifunctional: Supports measurement of wet steam, saturated steam, superheated steam, gases, and liquids.
- Integrated Compensation: Built-in temperature and pressure measurement, with straight pipe section compensation, saving space.
- Rugged and Safe: Dual-compartment housing, sturdy and durable, with high safety.
- Comprehensive Certifications: Passed multiple international certifications, such as burst test, vibration resistance test, and thermal shock test (150 K/s thermal shock).
- Maintenance-Free: No moving parts, no long-term drift or zero drift.
- Smart Functions: With heartbeat verification function, supports data transmission.
Measurement Principle
The 7F2C measures based on the Karman vortex street principle. When fluid passes a bluff body, vortices are alternately generated on both sides with opposite rotation directions. Each vortex creates a low-pressure zone, and the sensor detects pressure changes and converts them into electrical pulse signals.
Within the allowable range of the flowmeter, vortices are generated regularly, so the vortex frequency is proportional to the volumetric flow rate. The calibration coefficient (K-factor) is the proportionality constant, defined as pulses per volume unit. The K-factor depends only on the geometric structure of the flowmeter and is determined by calibration before delivery, so there is no long-term drift or zero drift.
Sensor and Materials
The vortex flowmeter uses a capacitive sensor, which has passed burst test, vibration resistance test, and thermal shock test, ensuring measurement performance, reliability, and structural stability.
Temperature measurement uses a Pt1000 temperature sensor, installed on the DSC sensor shaft, directly contacting the measured liquid.
For volumetric flow measurement, the materials of the DSC sensor and measuring tube can be 316L or Alloy C22, and can withstand high temperatures. For mass flow measurement, temperature measurement is built-in, i.e., temperature compensation.
Selection and Function Options
Only HART-type instruments can select the mass flow option with built-in pressure/temperature measurement. The selection code is steam mass flow or gas/liquid mass flow. Devices with this option can measure fluid pressure and temperature.
Pressure measurement is performed directly near the bluff body in the instrument. The pressure tap location should allow simultaneous measurement of pressure and temperature, ensuring high-accuracy fluid density and/or energy compensation based on pressure and temperature. The pressure measurement value is slightly lower than the pipeline pressure, so Endress+Hauser provides pipeline pressure correction (built into the device).
Calibration and Stability
After recalibration, the measuring device still maintains high stability, fully consistent with factory calibration. The parameter values after recalibration are within the specified measurement accuracy range of the flowmeter, applicable to volumetric flow measurement values, i.e., the main measurement variable of the device.
Straight Pipe Section Requirements and Compensation
The upstream straight pipe section length correction function can shorten the required upstream straight pipe section length, requiring only that the upstream straight pipe section length is not less than 10×DN. If the upstream straight pipe section is too short, the flowmeter can correct the resulting measurement error, but it depends on the degree of change in flow field morphology caused by throttling devices installed in the upstream pipeline.
Gas Measurement and Energy Calculation
The measuring device can calculate the density and energy of air and industrial gases based on proven standard calculation methods. Pressure and temperature effects can be automatically compensated via external or constant values, and it can measure single, mixed, and air, etc. It can also calculate chemical properties of natural gas, such as gross calorific value, net calorific value, etc.
Transmitter and Sensor
A device consists of a transmitter and a sensor. The integrated type has the transmitter and sensor as a single mechanical unit; the separate type has the transmitter and sensor installed separately. Below are schematic diagrams of the transmitter and sensor.
Transmitter
Sensor
There are many options for transmitters and sensors, which will not be detailed here.