Why is magnetic flow meter calibration necessary?
The accuracy of the magnetic flowmeter has been calibrated by the calibration line when it leaves the factory. However, at the use site, due to environmental conditions, fluid characteristics, and instrument damage such as component damage. It often causes instrument operation failures. Therefore, the electromagnetic flowmeter needs calibration. Ensuring accurate flow meter performance is an inestimable part of business planning and costing.
2 Magnetic flow meter calibration methods
At present, there are 2 solutions for Magnetic flow meter calibration: direct and indirect.
Direct Magnetic flow meter calibration is the excitation coil inspection method. This method is also known as the “dry standard” method of electromagnetic flowmeters. Indirect calibration is the external clamp-on ultrasonic flowmeter calibration method. Also known as the “non-contact measurement method”.
However, in the “dry standard” method, the standard coil is directly designed into the meter body of the flowmeter. The performance of its resistance and other indicators cannot be traced regularly.
As a result, it is impossible to determine whether the measurement characteristics of the standard coil change after a period of time. Therefore, “dry standard” is difficult to effectively realize the traceability of the value.
Compared with the “dry standard” method of detection. The external clamp ultrasonic flowmeter is capable of non-stop flow and non-cutting of pipes. The advantages of on-site Magnetic flow meter calibration are not affected by the temperature, pressure, and density of the fluid being measured.
Read more about: Digital Water Flow Meters
Magnetic flow meter calibration procedure
Clamp-on ultrasonic flowmeter calibration electromagnetic flowmeter
Calibration method: non-contact measurement method. That is, the external ultrasonic flowmeter is clamped on the pipe of the measured flowmeter. By comparing the cumulative flow error of the two flowmeters. Determine the measurement characteristics of the flowmeter being inspected.
The external ultrasonic flowmeter calibration method is used for on-site calibration. The inspector should first check whether the input of the key parameters that affect the accuracy of the measurement built in the flowmeter converter is correct.
Ask the staff about the daily flow rate, and observe and calculate the average flow rate of the flowmeter over a period of time.
Big data compared with standard equipment in the laboratory according to the standard table. Enter the pipe diameter of the standard meter and the flow meter to be inspected. Calibration coefficients, outer diameter, wall thickness and other parameters similar to the flow rate. According to the flowmeter’s online operating instructions on-site actual measurement input.
The cumulative flow method is used when calculating the indication error. Read the cumulative value of the flow of the standard meter and the meter under inspection for a certain period of time in three times. As the standard value of the measurement standard meter and the displayed value of the tested flow meter. Each measurement time is 30min.
Conditions permit or when the flow rate changes significantly within a day. Three flow points with obvious differences can be measured.
Real flow calibration electromagnetic flowmeter
How do you calibrate a magnetic flow meter?
- Select the corresponding pump according to the pipe diameter and flow rate for the verification test;
- If the system uses compressed air power. Turn on the air compressor to reach the air source pressure required by the system. To ensure the rapid switching of the commutator and the normal operation of the clamp meter;
- After the flowmeter is correctly installed and connected. It should be energized and preheated for about 30 minutes under the requirements of the verification regulations;
- If the high tank water source is used, check whether the overflow signal of the stabilized water tower appears.
- Before the formal test. According to the requirements of the verification regulations, use the verification medium to circulate the time in the pipeline system. At the same time, check whether there is any leakage in the sealing parts of the pipeline;
- Before starting the formal verification, the verification medium should be filled with the flowmeter sensor to be tested. Then turn off the downstream valve to adjust the zero position;
- When starting the verification, first open the valve at the front of the pipeline. Slowly open the valve behind the flow meter under test to adjust the flow at the verification point.
- During the calibration process, the flow stability of each flow point should be within the 1% ~ 2%-flow method, while the total amount law can be within 5%. When completing the verification process of a flow point, the temperature change of the verification medium should not exceed 1℃. When completing all the verification processes, it should not exceed 5℃. The pressure downstream of the inspected flowmeter should be high enough to ensure that no flashing and cavitation occur in the flow pipeline (especially in the reduced diameter);
- After each test, the valve at the front end of the test pipeline should be closed first. And then the pump should be stopped to avoid emptying the voltage stabilizing facility. At the same time, empty the remaining verification medium in the test pipeline. Then turn off the control system and the air compressor.
Magnetic flow meter calibration frequency
The verification period for flowmeters with accuracy grades of 0.2 and better than 0.2 is 1 year. For flowmeters with accuracy grades lower than 0.2 and using quoted errors, the verification period is 2 years.
The electromagnetic flowmeter is a flowmeter that calculates the flow rate by setting a magnetic field perpendicular to the flow direction in a closed pipeline. By measuring the induced electromotive force generated by the movement of the conductive liquid in the magnetic field.
The National Metrological Verification Regulations of the People’s Republic of China JJG 1033-2007 “Electromagnetic Flowmeter” 7.4 The verification period stipulates: The verification period of the flowmeter accuracy level of 0.2 and better than 0.2 is 1 year. For the accuracy level less than 0.2 The maximum verification period for the current level and usage reference error is 2 years.
Extended reading: Ultrasonic Insertion Flow Meter for Lined/Large Pipes
Do magnetic flow meters require calibration?
Mainly depends on your working conditions. If the measurement requirements are high. There are more impurities and dirt in the fluid and poor environmental conditions. Electrode fouling affects the measurement. The measurement is inaccurate after cleaning and repair. It can be verified. If the working conditions are good, the long-term use is normal. No verification is necessary.
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Sino-Inst flow calibration device and electromagnetic flowmeter production test standard
The manufacture of high-quality electromagnetic flowmeters is inseparable from high-precision flow calibration devices. The flow calibration device is the standard equipment for measurement departments and flowmeter manufacturers for value transmission, traceability and verification testing.
The Sino-Inst team has developed and built a set of high-level water towers as a voltage stabilization source. The static mass method is combined with the standard meter method, and is dedicated to the calibration device of the electromagnetic flowmeter.
The device uncertainty is better than the first-class fluid flow device level of 0.05%. It has passed the appraisal and audit of the Shaanxi Metrology Institute.
The 35-meter-high, 200-cubic-volume water tower is designed with a special overflow device. The fluctuation of the water level and liquid level during calibration measurement does not exceed 8mm. A high stability of better than 0.01% is achieved.
The production of MFE needs to go through various performance tests in a standard laboratory by an authoritative engineer before it can be put on the market.
Electromagnetic compatibility test
Electrostatic discharge (ESD) immunity GB/T 17626.2/ICE 61000-4-2
Electrical fast transient/pulse group (EFT/B) immunity GB/T 17626.4/ICE 61000-4-4
Surge (lightning strike) immunity GB/T 17626.5/ICE 61000-4-5
Power frequency magnetic field immunity GB/T 17626.8/ICE 61000-4-8
High and low-temperature cyclic impact test GB/T2423.1 GB/T2423.2
Salt spray test GB/T2423.17 GB/T6458
Vibration and shock test GB/T2423.10
Hazardous Substance Testing (RoHS): X-ray fluorescence spectroscopy testing IEC62321
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