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Vortex flowmeter initial installation precautions introduction

Vortex flowmeter initial installation precautions
(1) vortex flowmeter on-site installation completed power supply and pre-flow inspection
1) There should be no leakage in the flanges, valves, pressure measuring holes, temperature measuring holes and joints on the main pipe and the bypass pipe;
2) Whether the pipe vibration condition meets the requirements of the specification;
3) Is the sensor installed correctly? Is the electrical connection of each part good?
(2) Power on static debugging
The converter should have no output when the current is not flowing, the instantaneous flow indication is zero, and the cumulative flow does not change. Otherwise, first check whether the interference signal is introduced due to poor signal line shielding or grounding, or strong pipeline vibration. If it is not the above reasons, the potentiometer in the converter can be adjusted to reduce the amplifier gain or increase the trigger level of the shaping circuit until the output is zero.
(3) Dynamic debugging of flow through
The bypass valve is closed to open the upstream and downstream valves. After the flow is stabilized, the converter outputs a continuous pulse with uniform pulse width. The flow indication is stable and there is no jump, the valve opening is adjusted, and the output changes accordingly. Otherwise, the potentiometer should be carefully checked and adjusted until the meter output is false and no leakage. If the instrument is faulty, please refer to Table 7.
(4) Meter coefficient correction

The meter coefficient of the vortex flowmeter is verified under laboratory conditions. The working conditions at the time of use deviate from the laboratory conditions to correct the meter factor.
KVO=f/qv pulse number/m3 (16)
KV=EtEREDKVO(17)
Where KVO, KV-- are the instrument parameters under laboratory conditions and field working conditions, respectively;
Et--temperature correction factor;
ER--Reynolds number correction factor;
ED--tube diameter correction factor.
The rest of the symbols are the same as before.
Temperature correction factor Et
Et=1/[1+(2αb+αx)(t-to)] (18)
Where αb,αx-- are the linear expansion coefficients of the sensor body and the vortex generator, respectively (oC·mm)-1;
t, to - are the operating temperature and calibration temperature, oC.
Reynolds number correction factor ER
When expanding the measurement range, when the measurement exceeds the specified lower limit Reynolds number, the Reynolds number correction should be performed on the meter factor. Table 6 is the data provided by a factory (since the vortex generator is not standardized, the data in each plug may be different).
Table 6 Reynolds number correction factor ER
Reynolds number range
ER
Reynolds number range
ER
5×103<Re<6×103
6×103<Re<7×103
7×103<Re<8×103
8×103<Re<9×103
1.12
1.08
1.065
1.065
9×103<Re<104
104<Re<1.2×104
1.2×104<Re<1.5×104
1.5×104<Re<4×104
1.047
1.036
1.023
1.011
Pipe diameter correction factor ED
The diameter of the piping should meet the specified range. At this time, the actual deviation of the inner diameter of the piping and the sensor body can be corrected by the diameter correction factor ED.
ED=(DN/D)2 (19)
Where DN--the actual inner diameter of the sensor body, mm;
D--pipe inner diameter, mm.
(5) Fault phenomenon, cause and troubleshooting
There are many detection methods for vortex flowmeters. The difference between sensors and measurement circuits is also large. However, common faults of instruments have commonalities. Several instrument faults and countermeasures are listed in Table 7.
Fault phenomenon
possible reason
Approach
Output signal when there is no flow after power-on
1) Input shielding or poor grounding, introducing electromagnetic interference
2) The instrument is close to strong electric equipment or high frequency pulse interference source

3) The pipeline has strong vibration

4) Converter sensitivity is too high
1) Improve shielding and grounding, and eliminate electromagnetic interference
2) Keep away from interference sources and take isolation measures to enhance power supply filtering
3) Take shock absorption measures, strengthen signal filtering and reduce amplifier sensitivity
4) Reduce sensitivity and increase trigger level
No output signal after power-on
1) The power supply has failed
2) Input signal line is broken
3) A certain level of amplifier is faulty
4) Detection component damage

5) No flow or too small flow
6) The pipe is blocked or the sensor is stuck
1) Check the power and ground
2) Check signal lines and terminals
3) Check the working point and check the components
4) Check the sensing element and lead, check the valve, increase the flow or reduce the diameter
5) Check the cleaning pipe and clean the sensor
Output signal is not stable
1) Strong electrical interference signal
2) The sensor is stained or damp, and the sensitivity is lowered.
3) Sensor sensitivity is too high
4) Damaged sensor or poor lead contact
5) Two-phase flow or pulsating flow

6) Influence of pipeline vibration
7) Unstable process
8) Sensor installation is different or the gasket protrudes into the tube
9) Upstream and downstream valve disturbance
10) Fluid is not filled with pipes
11) The body has a wrap
12) There is cavitation
1) Strengthen shielding and grounding
2) Clean or replace the sensor to increase the amplifier gain
3) Reduce the gain and increase the trigger level
4) Check the sensor and lead
5) Strengthen process management to eliminate two-phase flow or pulsating flow phenomenon
6) Take shock absorption measures
7) Adjust the installation location
8) Check the installation and correct the inner diameter of the gasket
9) Lengthen the straight pipe section or add a flow regulator
10) Replacement of flow sensor location and method
11) Elimination of wraps
12) Reduce the flow rate and increase the pressure inside the tube
Large measurement error
1) Insufficient length of straight pipe
2) Analog conversion circuit zero drift or full scale adjustment is wrong
3) The power supply voltage changes too much
4) The meter exceeds the verification period
5) The difference between the inner diameter of the sensor and the pipe is large
6) Install different hearts or seals into the tube
7) Sensor contamination or damage
8) There are two-phase flow or pulsating flow
9) Pipeline leakage
1) Lengthen straight pipe section or add flow regulator
2) Calibration zero and span scale
3) Check the power supply
4) timely inspection
5) Check the inner diameter of the pipe and correct the meter factor
6) Adjust the installation and trim the gasket
7) Cleaning and replacing the sensor
8) Eliminate two-phase flow or pulsating flow
9) Eliminate leaks
Measuring tube leak
1) The pressure inside the tube is too high
2) The nominal pressure is not correct.
3) Seal damage
4) The sensor is corroded
1) Adjust the tube pressure and change the installation position
2) Select high-grade nominal pressure sensor
3) Replace the seal
4) Take anti-corrosion and protection measures
The sensor makes an unusual howling
1) The flow rate is too high, causing strong vibration
2) cavitation
3) Body loosening
1) Adjust the flow or replace the meter with large diameter
2) Adjust the flow rate and increase the flow pressure
3) Fastening body

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