Flowmeter problem

This is the most common flow technology, including orifice plate, venturi tube and sonic nozzle. DP flowmeter can be used to measure the flow velocity of most liquids, gases and vapors. DP flowmeter has no moving parts, which is widely used and convenient to use. However, pressure loss will occur after plugging, which will affect the accuracy. The accuracy of flow measurement depends on the accuracy of pressure gauge.

Volumetric flowmeter

PD flowmeter is used to measure the volume flow of liquid or gas. It introduces fluid into the metering space and counts the number of revolutions. Impeller, gear, piston or orifice plate are used to transfer fluid. PD flowmeter has high accuracy and is one of several methods to measure viscous liquid. But it will also produce unrecoverable pressure error, so it is necessary to equip with moving parts.

turbine flowmeter

When the fluid flows through the turbine flowmeter, the fluid makes the rotor rotate. The rotational speed of the rotor is related to the speed of the fluid. According to the average speed of the fluid sensed by the rotor, the flow rate or total amount is deduced. Turbine flowmeter can accurately measure clean liquid and gas. Like PD flowmeter, turbine flowmeter will produce unrecoverable pressure error and need moving parts.

Electromagnetic flowmeter

When a conductive fluid flows through an electromagnetic field, the velocity of the fluid can be obtained by measuring the voltage. Electromagnetic flowmeter has no moving parts and is not affected by fluid. When the tube is full, the accuracy of measuring conductive liquid is very high. Electromagnetic flowmeter can be used to measure the velocity of mud fluid.

supersonic flowmeter

Ultrasonic flowmeter usually uses propagation time method and Doppler effect method to measure the average velocity of fluid. Like other speedometers, it is an instrument for measuring volume flow. This is an unobstructed flowmeter. If the ultrasonic transmitter is installed outside the pipeline, it does not need to be inserted. It is suitable for almost all liquids, including mud, and has high precision. But the dirty pipeline will affect the accuracy.

vortex shedding flowmeter

Vortex flowmeter is to place a streamlined vortex generator in the fluid, and the speed of vortex is proportional to the speed of fluid, thus calculating the volume flow. Vortex flowmeter is suitable for measuring liquid, gas or steam. It has no moving parts and no dirt problem. Vortex flowmeter will produce noise, and it needs high velocity of fluid to produce vortex.

Thermal mass flowmeter

The fluid velocity is measured by measuring the increase of the fluid temperature or the decrease of the thermal sensor. Thermal mass flowmeter has no moving parts or holes, so it can accurately measure gas flow. Thermal mass flowmeter is one of the few technologies that can measure mass flow, and it is also one of the few technologies used to measure large-caliber gas flow.

Coriolis flowmeter

This kind of flowmeter is measured by using the deflection of vibrating fluid tube corresponding to mass flow. Coriolis flowmeter can be used to measure the mass flow of liquid, mud, gas or steam. High accuracy. However, the pipeline wall should be maintained regularly to prevent corrosion.

Electromagnetic flowmeter

Measurement principle: Faraday's law of electromagnetic induction proves that the movement of a conductor in a magnetic field induces an electric potential. According to the principle of electromagnetic measurement, fluid is a moving conductor. The induced potential is proportional to the flow rate and is detected by two measuring electrodes. Then the transmitter amplifies it and calculates the flow according to the cross-sectional area of the pipeline. The constant magnetic field is generated by replacing the changing switching DC current with magnetic poles.

The measuring system consists of a transmitter and a sensor.

It has two models: integrated type, in which the transmitter and sensor form a complete mechanical unit; Separate type, transmitter and sensor are installed separately.

Transmitter: Promag50 (operated by buttons and displayed in two lines) Sensor: PROMAGW (DN25...2000)

technical parameter

Measurement variable: flow.

Measurement range of input variable: typical v=0. 1 ... 10m/s, with specified measurement accuracy.

Operating flow range: exceeding 1000: 1.

Input signal status input (auxiliary input): U=3…30vDC, Ri = 5kΩ, electrically isolated. Configurable: cumulative reset, measured value suppression and error information reset. Current input (Promag 53 only): active/passive optional, electrical isolation resolution: 2μA Active: 4. . . 20mA, ri ≤150Ω, Uout=24V DC, current short-circuit resistance.

Passive: 0/4. . . 20mA，Ri≤ 150ω，Umax=30V DC .

Output variable

Output signal current output: active/passive optional, electrically isolated, time constant optional (0.05... 100s), full-scale value optional, temperature coefficient: 0.005%o.r./℃ typical; Resolution: 0.5 μA

Active: 0/4...20ma, RL

Passive: 4...20ma, maximum 30VDC, RI ≤150Ω.

Pulse/frequency output:

Passive, open collector 30 VDC, 250 mA, electrically insulated.

Frequency output: the full-scale frequency is 2 ...1000 Hz (f max =1250 Hz), and the on/off ratio is 1: 1.

Pulse width: max. 10。

Pulse output: the pulse value and polarity can be selected, the maximum pulse width (0.05...2s) can be set, and the maximum pulse frequency can be selected from the shell of the material transmitter. The integrated shell: powder spray coating cast aluminum; Wall-mounted shell: cast aluminum

Sensor shell, DN25...300: powder spray coating cast aluminum; DN350...2000: coated steel

Model specification: 50W9h-UD0A 1K2C4 AW (DN 900), 50W is 50 series; 9H represents a diameter of 900 mm (DN 900); U represents that the base material is polyurethane; D indicates that the process connection/material is PN 10 DIN 250L and ST37-2 flange (applicable to DN 200-DN 2000); 0 indicates that the electrode material (all electrodes) is 1.4435/3 16L stainless steel; A stands for 0.5%.3 point calibration; 1 means that no special authentication is required; The second a means there is no riot requirement; K indicates that the protection level of the enclosure is IP68, separated and wall mounted; 2 stands for separated self-contained 10m cable;

Environmental conditions: ambient temperature -20...+60℃ (sensor, transmitter), installed in the dark, avoid direct sunlight, especially in warm climate areas.

The reference conditions of measurement accuracy: DIN 19200 and VDI/VDE 264l, medium temperature: +28℃ K, ambient temperature: +22℃ K, preheating time: 30min,

During installation, it should be noted that accurate measurement can only be obtained when the pipeline is full, and the following installation positions should be avoided:

Installed at the highest point of the pipeline (easy to accumulate bubbles)

Directly installed in front of the opening and outlet of the downward pipeline.

Be careful not to install the flow tube on the inlet side of the pump, so as not to damage the flow tube lining due to pump pressure. When using reciprocating pump, diaphragm pump or plunger pump, it is necessary to install pulse throttle valve.

When the length of the downward pipeline exceeds 5m, install a siphon or a bleeder valve behind the sensor. So as to avoid possible damage to the inner wall of the measuring tube caused by low pressure. Make sure the pipe is full and reduce the gas content.

Installation direction: the most suitable direction helps to avoid gas accumulation and residue accumulation in the measuring tube.

Vertical installation; This orientation is ideal for the pipeline system which is easy to self-empty, and the empty pipe detection electrode may not be added.

Horizontal installation: the plane of the measuring electrode must be horizontal, which can prevent the electrode from being insulated for a short time due to air bubbles. Note: the empty pipe detection function can only work normally when the measuring device is installed horizontally and the transmitter shell is facing up. If the vibration is very severe, the sensor and transmitter should be installed separately.

Pedestal and bracket: If the nominal diameter DN≥350, install the transmitter on the pedestal that can bear enough load. Please note that the external frame is not allowed to support the weight of the sensor. This will deform the external frame and damage the internal excitation coil. If possible, it is best to avoid valves, tees and elbows when installing sensors.

Ensure the following required inlet and outlet straight pipe sections to ensure the measurement accuracy: inlet length >; 10 × DN outlet length >: 5 × DN sensor and transmitter grounding sensor are in the center of the pipeline.

Grounding: The sensor and the medium must have the same potential to ensure the measurement accuracy and avoid electrode corrosion damage. Equipotential is ensured by installing a grounding reference electrode in the sensor. If the medium flows in an unlined and grounded metal tube, the grounding requirements can be met by connecting to the transmitter housing. For individual grounding, the same as above.

Note: If you are not sure whether the medium is properly grounded, you should install a grounding ring.

Fault diagnosis:

Electromagnetic flowmeter

If a fault occurs after startup or during operation, it is usually diagnosed according to the following checklist to directly find the cause of the problem and the corresponding solution.

Inspection shows

No display and no output signal: 1, check the power supply terminal 1, 2; 2. Check the fuse.

No display but signal output: 1. Check whether the cable connection of the display module is correctly inserted into the amplifier board; 2. The display module is damaged; 3. The measuring electrode is damaged.

Foreign language display text: Turn off the power, press and hold the+/-key at the same time, and power on the instrument. The display text is English (default), with the maximum display contrast.

The measured value is displayed, but there is no current or pulse output signal: the measuring electrode is damaged.

Display fault:

Faults during debugging or measurement will be displayed immediately.

The fault information will contain some symbols with the following meanings: S= fault information P= process fault.

= Fault information! = Warning message Empty pipe = Fault type, that is, the measuring pipe is partially full or completely empty.

03: 00: 05 = failure time, hours/minutes/seconds #40 1= failure code.

Current output: the minimum current is 4-20ma (25ma) → 2ma, and the output signal corresponds to zero flow;

Maximum current, 4-20ma (25ma) → 25ma.

Note: System or process failures defined as "warning messages" have no impact on input/output.