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The flow meter measurement is not accurate, ask you what to do? Try these tricks!

Aspect 01 electromagnetic flowmeter is not allowed

1. The liquid contains bubbles;

2. Non-full tube causes measurement inaccuracy;

3. Electromagnetic flowmeter electrode corrosion causes measurement inaccuracy;

4. The conductivity of the measured medium is too low, resulting in inaccurate measurement;

5. Electromagnetic flowmeter electrode fouling and electrode short circuit lead to inaccurate measurement;

6. The deformation of the electromagnetic flowmeter lining leads to inaccurate measurement;

7. The external strong electric field causes the measurement to be inaccurate;

8. The grounding effect of the electromagnetic flowmeter is not good;

9. The installation position of the electromagnetic flowmeter does not meet the requirements.

Aspect 02 Turbine flow meter is not allowed

1. The pulsation of the water source affects the flow volatility.
Solution: Increase the straight pipe distance between the pump and the flow meter to stabilize the flow.

2. The installation position of the turbine flowmeter is too close to the position of the valve or the elbow. When the raw material passes through the valve or the bent pipe, the flow fluctuates.
Solution: At this time, it should be away from the valve and elbow position to ensure that a certain straight pipe section is a good way to solve the problem.

3. There are motor, inverter, strong current and other sources of interference near the turbine flowmeter.
Solution: Ground the meter meter or add a filter capacitor. If the problem still cannot be solved, the best way is to stay away from the source of interference.

4, turbine flowmeter no flow display: first check the line for problems, such as signal line off, there are broken lines. Separate the sensor from the signal amplifier, connect the signal amplifier to the meter, and use the ferrous metal to swipe back and forth at a distance of 2~3mm from the bottom of the amplifier that takes the signal. If the meter has a display, the display part has no problem.
Solution: Remove the flow sensor from the pipe and check if the flowmeter impeller is entangled or the impeller is damaged.

5. The flow meter shows that the flow rate is smaller than the actual flow rate: the general cause of this problem is that the impeller rotates not smoothly or the blade breaks.
Solution: Remove the flowmeter from the pipe and check if the flowmeter is entangled or damaged.

6. The flowmeter display error is relatively large: first check whether the flow sensor coefficient, ie, the K value and other parameters of the instrument are set correctly; if there are conditions, use the electronic scale to perform actual calibration and calibration.
Solution: If the flow is not repeatable or cannot be calibrated at all, contact the supplier.

Watch 03 vortex flowmeter is not allowed

1. The vortex flowmeter is connected to the power supply, the valve is not open, and there is a signal output.
Solution: 1 sensor (or detection component) output signal shielding or grounding is poor, attracting external electromagnetic interference; 2 instrument is too close to high-voltage equipment or high-frequency equipment, space electromagnetic radiation interference, affecting the instrument; 3 installation pipeline There is strong vibration; the sensitivity of the 4 converter is too high, and the interference signal is too sensitive; the measures to be taken are to strengthen the shielding and grounding, eliminate the vibration of the pipeline, and adjust the sensitivity of the converter.

2. The vortex flowmeter in intermittent working state, the power supply is not broken, the valve is closed, and the output signal does not return to zero; the main reason may be the influence of pipeline oscillation and external electromagnetic interference.
Solution: The sensitivity of the converter should be lowered to increase the trigger level of the shaping circuit, which can suppress noise and overcome false triggers during the interval.

3. In the power-on state, the downstream valve is turned off, the output does not return to zero, and the upstream valve output returns to zero. This is mainly caused by the fluid pulsation pressure upstream of the disaster flow meter. If the vortex flowmeter is installed on a T-branch and the upstream main pipe has pressure pulsation, or if there is a pulsating power source upstream of the vortex flowmeter (such as a piston pump or a Roots blower), the pulsating pressure causes vortex flow. The fake signal.
Solution: Install the downstream valve upstream of the vortex flowmeter and close the upstream valve during shutdown to isolate the effects of pulsating pressure. However, when installing, the upstream valve should be as far away as possible from the vortex flowmeter and ensure sufficient straight pipe length.

4. In the power-on state, the output of the upstream valve is not returned to zero, only the output of the downstream valve is returned to zero. This fault is caused by the fluid disturbance in the pipe, and the disturbance comes from the downstream pipeline of the vortex flow meter. In the pipe network, if the straight pipe section downstream of the vortex flowmeter is short and the outlet is close to the valves of other pipes in the pipe network, the fluid disturbance in these pipes (such as the valves in the other downstream pipes open, close, and adjust the valve frequently) Action) Passed to the vortex flowmeter detection component, causing a false signal.
Solution: Lengthen the downstream straight pipe section to reduce the impact of fluid disturbance.

5. After power-on and through-flow, the output (or indication) signal of the vortex flowmeter does not change with the flow rate. Due to the poor grounding of the shielding layer of the signal line or the improper selection of the grounding point, the external electromagnetic interference is very serious (for example, 50Hz power frequency interference). The weak vortex signal is completely suppressed, and the output signal is completely submerged by noise interference. At this time, adjusting the valve opening degree and the gain of the meter are useless. The connection between the detecting component and the converter is broken, the input end of the preamplifier is open, or the detecting component has a signal line shorted to the ground, causing serious imbalance of the preamplifier input, and the common mode interference is down, and the vortex street The signal is suppressed by noise interference and the output is completely controlled by interference. The gain of the preamplifier is too high, causing self-oscillation and the output is locked at the self-excited frequency.
Solution: The above is a fault caused by electrical reasons. Only by strengthening the shielding and grounding, reasoning the wiring, reducing or eliminating the interference, the instrument can recover normally.

6. Strong vibration of the pipeline (or environment). When the vibration direction is consistent with the sensitive direction of the instrument detection component, the vibration completely suppresses the vortex signal, and the output signal is the vibration frequency signal. Adjusting the valve opening does not change the output. solution
Solution: Use vibration-damping measures (plus pipe anti-vibration seat, fixed pipe), clarify the direction of vibration, turn the sensor of the vortex flowmeter around the pipe axis by 90 °C, adjust the sensitive direction of the detecting component to the direction of vibration. Vertically, the influence of the vibration can be reduced or the gain and trigger sensitivity of the preamplifier can be appropriately reduced. Take the above measures to eliminate the effects of vibration.

7. The “locking” of the pulsating flow to the vortex signal. Without the effective suppression of the pulsating flow, the pulsating flow can not underestimate the vortex stable separation. If the pulsation frequency matches the vortex signal frequency, it may be vortex. The signal is "locked" near this frequency, at which point the valve and meter sensitivity are adjusted and the output signal frequency does not change.
Solution: Take measures to absorb or reduce fluid pulsation during the design and construction of the installation piping of the instrument.

8. When the meter exceeds the verification period, the meter coefficient K changes; the set parameters (such as the inner diameter of the measuring tube, the standard state density and the meter factor) are incorrect; the zero drift or range adjustment of the analog conversion circuit is incorrect; the power supply is excessively deviated. The rating or ripple is too large.
Solution: Quickly send the meter for inspection, check the set parameters in time, and regularly adjust the zero and range of the meter to maintain the integrity of the meter.

9. The vortex flowmeter transmits a abnormal whistling sound: (1) the flow rate is too high, causing the body or the detecting component to vibrate; (2) cavitation occurs in the pipe; (3) the generating body or the detecting component is loose .
Solution: In order to avoid damage to the generating body or detecting component, first adjust the valve to reduce the flow rate and reduce the flow rate, and further find out the cause.

10. Problems with selection. Some vortex sensors have a large selection of specifications on the caliber selection or after design selection, so the actual selection should be as small as possible to improve the measurement accuracy. For example, a vortex pipeline is designed for use by several equipment. Because some of the equipment is not used sometimes, the actual actual flow is reduced. The actual design results in too large an original design, which is equivalent to an increase in measurable flow. The lower limit, when the process pipe is small, the indication is not guaranteed. When the flow is large, it can be used, because it is sometimes too difficult to rebuild. Changes in process conditions are only temporary.
Solution: The parameter can be re-tuned to improve the indication accuracy.

11, the reason for the direction of the parameter setting. The instrument is incorrectly indicated due to a parameter error. The parameter error makes the secondary meter full frequency calculation error. The full-scale frequency is similar to the indication that the long-term inaccuracy is indicated. The full-scale frequency of the actual full-scale frequency calculation indicates that the range is fluctuating and cannot be read. The inconsistency of the parameters on the data affects the final determination of the parameters.
Solution: Finally, the problem was solved by recalibrating and determining the parameters by comparing with each other.

12. The secondary instrument is faulty. There are many faults in this part, including: when the instrument board is disconnected, the range setting has individual bit display bad, and the K coefficient setting has individual bit display bad, which makes it impossible to determine the range setting and K factor setting.
Solution: The problem can be solved by fixing the corresponding fault.

13, four-way line connection problem. On the surface of some circuits, the line connection is very good. Careful inspection, some connectors are actually loose and the circuit is interrupted. Some connectors are tightly connected, but the fastening screws are fastened to the wire sheath due to the secondary line problem, which also makes the circuit Interrupted.
Solution: Rewire.

14. The circuit always has no indication due to the failure of the secondary instrument flat-axle cable. Due to long-term operation, coupled with the impact of dust, flat-panel cable failure.
Solution: The problem is solved by cleaning or replacing the flat shaft wires.

15. Use environmental issues. Especially in the sensor part installed in the well, the circuit board is damp due to the high humidity.
Solution: Through the corresponding technical improvement measures, the sensor part with large humidity is re-disposed to separate the probe part and the conversion part, and the separate type sensor is used. Therefore, the working environment is good, and the instrument has been running well.

16. Due to the poor adjustment of the site, or due to the actual changes after the adjustment. Due to the on-site vibration and noise balance adjustment and sensitivity adjustment is not good. Or the indication of the problem caused by the change of the situation on the spot after running for a period of time after the adjustment.
Solution: Use an oscilloscope, plus the combined process operation, re-adjust.

Watch 04 orifice flowmeter is not allowed

1. The differential pressure pipeline is blocked, and the differential pressure pipeline is dredged;

2. Differential pressure gauge failure, check differential pressure gauge;

3. The differential pressure transmitter indicates a significant deviation, and the scale value should be checked;

4. The installation direction of the throttling element is incorrect, and the throttling element is reinstalled;

5. The parameters of the measured medium condition are inconsistent with the parameters used in designing the throttling device, and are corrected according to the relevant formula. If necessary, the differential pressure value should be recalculated;

6. The length of the straight pipe section before and after the throttling device is not enough, and the length of the straight pipe section should be adjusted;

7. The inner diameter of the straight pipe section is out of tolerance, the inner diameter of the straight pipe section is measured, and the maximum flow rate is recalculated;

8. The throttle aperture is out of tolerance, the measured throttle aperture is recalculated, and the maximum flow is recalculated;

9. The throttling element is deformed and the throttling element is replaced;

10. There are attachments on the throttling element, and the throttling element is cleaned and replaced;

11. The sharp side of the orifice plate should face the fluid flow direction as the inlet end, and the flared side is the outlet end. If it is reversed, the display will be much smaller.
Solution: Check the installation direction of the orifice plate and install the orifice plate correctly.

12. The entrance edge of the orifice plate is worn. If the orifice plate is used for a long time, especially when the measured medium is mixed with solid particles and other impurities, the geometry and size of the orifice plate will change, and if the opening is enlarged, Or the edge of the opening becomes dull, the measured pressure difference will become smaller, and the flow rate display will be lower.
Solution: Rework the orifice plate.

13. Transmitter zero drift: If the usage time is long, the zero point of the transmitter may drift. If it is negative drift, the display pressure difference will decrease and the displayed flow rate will also decrease.
Solution: Correct the zero point of the transmitter.

14. The length of the upstream and downstream straight pipe sections is not enough. If the upstream and downstream straight pipe sections are not long enough, the gas will not be fully developed, which will cause a large error in the measurement results. If there are multiple elbows in the upstream straight pipe section, the metering will be made. The result is low.
Solution: Renovate the steam pipeline, which is the length of the upstream and downstream straight pipe sections. A rectifier is added in front of the throttling device.

15. The three-valve of the differential pressure transmitter leaks. If the high-pressure valve of the three-valve group leaks, the differential pressure will be reduced and the measurement result will be low.
Solution: If the high pressure valve in the three valve group leaks, tighten the valve and replace if necessary. If the balance valve in the three valve group leaks inside, tighten the valve and replace if necessary.

Aspect 05 Rotameter is not allowed

1. The reason why the pointer does not move when the system is turned on: the medium contains impurities, which makes the rotor jam; the working pressure of the system is too small, causing the meter to not work properly.
Solution: Remove foreign matter; increase magnetic filter to increase system working pressure.

2. The reason why the pointer does not recover is that the medium contains impurities, which makes the rotor jam; the instrument selection is not suitable, and the instrument is too small.
Solution: remove foreign matter and increase the magnetic filter;

3, the reason that the pointer fluctuation is too large: can not accurately read, the cause: the system working pressure is unstable; the medium has pulsating flow or two-phase flow phenomenon; the pipe diameter change at the inlet and outlet of the instrument leads to pressure change or pressure loss increase.
Solution: Check your system; eliminate pulsating flow and two-phase flow. Reduce pressure loss.

4. The reason why the pointer does not return to zero: the pointer is displaced due to the fluctuation of the meter; the parts in the measuring tube are bent and deformed due to the up and down impact of the meter.
Solution: Loosen the small screw at the pointer to restore the pointer to the inoperative state; it is recommended to return it for repair or replacement.

5, the remote transmission is not accurate Cause: the ambient temperature exceeds the working requirements; the transmitter drifts.
Solution: Use as required; adjust the potentiometer or adjustment screw in the transmitter to restore normal.

6. No display when the fluid is flowing normally, the total number of counters does not increase: check the power cord, fuse, function selection switch and signal line for open circuit or poor contact; check the internal printing plate of the display, contact parts, etc. for poor contact; Check the detection coil; check the internal fault of the sensor. The above 1-3 items are all confirmed to be normal or have been eliminated, but there is still a fault phenomenon, indicating that the fault is inside the sensor flow channel, and it can be checked whether the impeller touches the inner wall of the sensor, and whether there is a foreign matter card. Live, shaft and bearing are free of debris or breakage.
Solution: Use ohmmeter to check the fault point; print board fault check can replace the "alternate version" method, replace the fault board and make a detailed inspection; do the position mark of the detection coil on the sensor body, unscrew the test head, use The iron piece moves quickly under the detecting head. If the number of counters does not increase, the coil should be inspected for broken wires and solder joints. The foreign matter is removed, and the damaged parts are cleaned or replaced. After the recovery, the air blows or the hand moves the impeller. No friction sound, after re-calibrating parts such as bearings, re-verify and obtain a new meter factor.

7. The flow operation is not reduced, but the flow display is gradually decreased: whether the filter is clogged, if the filter differential pressure increases, indicating that the debris has been blocked; the valve on the flow sensor pipe section has a loose spool, and the valve opening is automatic. Reduced; the sensor impeller is obstructed by debris or the bearing gap enters the foreign object, the resistance increases and the deceleration slows down.
Solution: Eliminate the filter; judge from the valve handwheel whether it is adjusted effectively, and then repair or replace it after confirming; remove the sensor to clear and re-verify if necessary.

8, the fluid does not flow, flow display

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