The flowmeter is one of the most commonly used instruments in the industry. It masters the troubleshooting methods of common flowmeters in order to judge and solve the problems encountered in the production process in a timely manner. Flowmeter classification
★ There are many kinds of flow measurement methods and instruments, and there are many classification methods. So far, there are more than 60 types of flow meters available for industrial use.
★ There are two types of closed pipes and open channels according to the measuring objects.
★ According to the purpose of measurement can be divided into total measurement and flow measurement, the instrument is called the total volume and flowmeter.
★ According to the principle of measurement divided into mechanical principles, thermal principles, acoustic principles, electrical principles, optical principles, principles of atomic physics.
★ According to the current most popular and extensive classification, it can be divided into volumetric flowmeter, differential pressure flowmeter, floater flowmeter, turbine flowmeter, electromagnetic flowmeter, vortex flowmeter, mass flowmeter and ultrasonic flow. Meters and so on.
Common flowmeter faults and treatment methods
Volumetric flowmeter
Waist wheel flow meter
phenomenon
the reason
Treatment measures
Waist wheel does not turn
1. Dirty material stuck in the pipe.
2. The measured liquid solidifies.
1. Clean the pipe, filter and flow meter.
2. Dissolve the liquid.
The waist wheel rotates and the pointer does not move or when it stops
1. The head fork disconnected.
The head gearbox enters the dirt.
2. The pointer or counter stuck.
3. There is a disconnection in the transmission.
Remove the watch head, turn the fork by hand, and the meter rotates. Then the head and shaft are out of contact; if not, check it step by step.
Steering seal shaft leak oil
Seal packing wear
Tighten the gland or replace the packing.
Device offset compensation and small flow error
The waist wheel collides with the housing due to wear of the bearing or displacement of the fixed drive gear body.
Replace the bearing, check the drive gear, whether the wheel body is rotating, and whether the screw fixing the gear is loose.
Large variation in error
1. The fluid pulsates more.
2. Contains gas.
1. Reduce pulsation.
2. Add an air eliminator.
Oval gear flow meter
phenomenon
the reason
Treatment measures
Rotor does not rotate
1. The filter is clogged.
2. Impurities enter the flowmeter and cause the rotor to jam.
1. Clean the filter.
2. Inspect the filter for damage and clean the inside of the flowmeter.
The rotor rotates normally and the counter does not count
1. Gear change gear meshing bad.
2. The riveting or pinning off of each connecting part.
1. Remove the counter and check the transmissions and counters at all levels.
2. Do not subject the magnetic coupling to excessive torque, otherwise it will demagnetize due to the wrong polarity.
Steering seal shaft leak oil
Seal packing wear
Tighten the gland or replace the packing.
Mechanical seal coupling leak
1. The gland is too loose.
2. Filler wear.
Replace the packing and fill it with seal oil.
The indicated value is less than the actual value
1. Flow exceeds the specified range.
2. Medium viscosity is too small.
3. The rotor and other rotating parts are not flexible.
1. Make the flow within the specified range or change the flow meter specification.
2. Recalibrate and replace the adjustment gear to correct it.
3. Check the rotor, bearings, drive gears, etc., and replace worn parts.
The indicated value is greater than the actual value
1. The flow has large pulsations.
2. The medium is mixed with gas.
3. Medium viscosity is too large.
1. Reduce the pulsation of the flow in the pipeline.
2. Install degasifier.
3. Recalibrate, replace the adjustment gear pair and correct it.
2 differential pressure flowmeter
phenomenon
the reason
Treatment measures
Indicates zero or small movement
1. The balance valve is not fully closed or leaking.
2. Throttle device roots high and low pressure valves are not open.
3. The throttling device to the differential pressure gauge valve, pipeline blockage.
4. The vapor pressure tube is not completely condensed.
5. The gasket between throttling device and process piping is not tight.
6. Differential pressure gauge internal failure.
1. Close the balance valve and repair or replace it.
2. Open the high and low pressure valves.
3. Flush the tubing, repair or change valve.
4. Open the watch after it is completely condensed.
5. Tighten the bolts or replace the pads.
6. Check, repair.
The indication is below zero
1 high and low pressure pipeline reverse connection.
2. The signal line is reversed.
3. Severe leakage or rupture of the high pressure side piping.
1-2. Check and connect properly.
3. Change parts or change pipes.
Low indication
1. The high pressure side piping is not tight.
2. The balance valve is loose or not closed.
3. The high pressure side piping air is not drained.
4. Differential pressure meter or secondary instrument zero offset or displacement.
5. The throttling device and differential pressure gauge are not equipped and do not meet the design requirements.
1. Check and eliminate leaks.
2. Check, close or repair.
3. Drain the air.
4. Check and adjust.
5. Replace the supporting differential pressure gauge.
High indication
1. The low pressure side piping is not tight.
2. Air is accumulated in the low pressure side piping.
3. The vapor pressure is lower than the design value.
4. Differential pressure gauge zero drift.
5. The throttling device and differential pressure gauge are not suitable.
1. Check and eliminate leaks.
2. Drain the air.
3. Correct the actual density.
4. Check and adjust.
5. Replace the differential pressure gauge.
Indicating large fluctuations
1. The flow parameter itself fluctuates too much.
2. The load cell is sensitive to parameter fluctuations.
1. The high and low pressure valves are closed properly.
2. Adjust the damping effect properly.
Indication does not move
1. Failure of anti-freeze facility, hydraulic freezing in differential pressure gauge and pressure guiding pipe.
2. The high and low pressure valves are not open.
1. Strengthen the effectiveness of antifreeze facilities.
2. Open the high and low pressure valves.
3 metal float flowmeter
phenomenon
the reason
Treatment measures
Float meter pointer jitter
1. The media pulsates.
2. The pressure is unstable.
1. Increase the damping.
2. The use of voltage regulator or steady flow device.
The pointer stops at a certain position
1. Open the valve too fast and the float stuck.
2. The float guide rod is not concentric with the stop ring.
1. Slow down valve opening speed.
2. Remove the meter adjustment.
Large measurement error
1. The installation does not meet the requirements.
2. The density of the liquid medium varies greatly.
3. Temperature and pressure effects are greater.
4. Pipe vibration.
1. The vertical or horizontal installation angle is not more than 20 degrees.
2. Calculate the error correction factor and multiply the reading by the actual flow rate.
3. Use warm pressure compensation.
4. Find a professional to adjust the position of the parts.
4 turbine flow meter
phenomenon
the reason
Treatment measures
No flow when fluid is flowing normally
1. Power lines, fuses, etc. have open circuit or poor contact.
2. The display has poor internal contact.
3. The coil is broken.
4. There is a problem inside the Sensor flow channel.
1. Use an ohmmeter to troubleshoot.
2. Check by replacing "backup" method.
3. Check whether the coil is broken or soldered off.
4. Remove sensor foreign objects and clean or replace damaged parts.
Flow shows a gradual decline
1. The filter is clogged.
2. The valve spool on the sensor spool is loose and the valve opening is reduced.
3. The resistance of the sensor impeller is impeded by debris or the clearance of the bearing enters the foreign material, and the resistance increases.
1. Clean the filter.
2. From the valve handwheel adjustment is effective judge whether the spool is loose.
3. Remove the sensor to remove debris and recheck if necessary.
Fluid does not flow, flow is not displayed as zero
1. The shield of the transmission line is badly grounded.
2. The pipeline vibrates and the impeller shakes.
3. The shutoff valve is not closed.
4. The internal circuit boards or the electronic components of the display are deteriorating.
1. Check for good grounding.
2. Reinforce the pipeline, or install brackets before and after the sensor to prevent vibration.
3. Check or replace the valve.
4. Take a "short-circuit method" or item-by-item inspection to determine the source of the interference and identify the point of failure.
Significant difference between display instrumentation and experience evaluation
1. Sensor internal flow channel internal failure.
2. The back pressure of the sensor is insufficient, and air pockets occur, affecting the rotation of the impeller.
3. Reasons for pipeline flow.
4. The internal fault of the display.
5. Permanent magnetic material elements in the detector are deactivated during aging.
6. The actual flow rate of the sensor has exceeded the specified range.
1-4. Find the cause of the problem and find a solution to the specific cause.
5. Replace the loss of magnetic components.
6. Replace the appropriate sensor.
5 electromagnetic flowmeter
phenomenon
the reason
Treatment measures
Instrument no-flow signal output
1. The meter power supply is abnormal.
2. The cable connection is abnormal.
3. Liquid flow conditions do not meet the requirements.
4. The sensor components are damaged or there is an adhesive layer on the inner wall.
5. The converter components are damaged.
1. Check whether the output voltage of the power circuit board is normal.
2. Connect the cables correctly.
3. Check the direction of liquid flow and whether the liquid in the tube is full.
4. Periodically clean up the covered liquid layer.
5. Replace damaged components.
Fluctuation of output value
1. Electromagnetic interference from external stray currents.
2. The pipe is not full of liquid or contains bubbles in the liquid.
3. The power board of the flowmeter is loose.
1. Check whether there is a large electric appliance or electric welding machine at work in the instrument operating environment.
2. Make the liquid full or bubble flat.
3. Disassemble the flowmeter and re-fix the circuit board.
Flow measurement does not match actual value
1. Transmitter board failure.
2. The liquid flow rate is too low and contains tiny bubbles.
3. The signal cable connection is not good.
4. The converter's parameter settings are inaccurate.
1. Check that the transmitter circuit board is intact.
2. Ensure that the flow rate of the measured liquid in the pipeline is above the minimum flow limit.
3. Check that the signal cable connection and the cable insulation are intact.
4. Set the converter setpoint again and verify the zero and span values ​​of the converter.
Output signal overrange
1. There is an error in the signal cable connection.
2. The converter's parameter settings are incorrect.
3. The converter and sensor model are not matched.
1. Check the signal loop connection.
2. Check if each parameter setting and zero point and full scale of the converter meet the requirements.
3. Reverse the transducer and sensor model.
6 vortex flowmeter
phenomenon
the reason
Treatment measures
Pipe flow meter without output
Instrument no display no output
1. The power supply has failed.
2. The power supply is not connected.
3. The connection cable is broken or the boundary is wrong.
1. Reapply power or replace the power supply.
2. Turn on the power.
3. Reconnect the wiring and check the cable.
Instrument shows no output
1. The flow rate is too low to enter the measurement range.
2. There is something wrong with the amplifier board.
3. The probe body is damaged.
4. The pipe is blocked or the sensor is stuck.
1. Increase the flow or reselect the flow meter.
2. Replace the motherboard.
3. Replace the probe.
4. Reinstall the meter.
phenomenon
the reason
Treatment measures
No flow after power on but output
The output signal is stable
1. The output frequency is 50 Hz power frequency interference.
2. The amplifier board is damaged and generates self-excitation.
1. Use a shielded cable and reconnect according to the regulations.
2. Replace the amplifier.
Output signal changes
1. There are strong electric devices or high frequency interference near the flow meter.
2. The pipeline has a strong turbulence.
3. The magnification or trigger sensitivity of the amplifier board is too high.
4. The pipeline valve is not completely closed and there is leakage flow.
1. Select the installation location again.
2. Reinforce the piping of the flowmeter installation section.
3. Decrease the magnification (GB) or sensitivity (SB) counterclockwise.
4. Check the valve.
phenomenon
the reason
Treatment measures
Unstable flow output
Selection installation is extremely piping reason
1, there is a strong electrical interference signal, the instrument is not grounded, flow and interference signal superposition.
2. The straight pipe section is not enough or the inner diameter of the pipe is inconsistent with the inner diameter of the meter.
3, the impact of pipeline vibration.
4, flow meter installation of different hearts.
5, the fluid is full.
6. The flow rate is lower than the lower limit or exceeds the upper limit.
7. There is cavitation in the fluid.
1. Reconnect the shielded ground.
2. Replace the installation location again.
3. Reinforce the pipe to reduce vibration.
4. Reinstall the meter.
5. Check fluid flow is extremely instrument mounting position.
6. Increase the decrease flow or adjust the amplification board filter parameters.
7. Install downstream valves on the instrument to increase back pressure.
Instrument reason
1, the instrument menu settings are wrong.
2, the motherboard is damaged.
1. Re-set the menu as required.
2. Replace the motherboard.
7 mass flow meters
phenomenon
the reason
Treatment measures
Instantaneous flow rate constant maximum
1. The cable is disconnected or the sensor is damaged.
2. The fuse in the transmitter burns out.
3. The sensor measuring tube is blocked
1. Replace the cable or replace the sensor.
2. Replace the fuse.
3. After dredging, tapping the sensor housing and measuring the AC and DC voltages is still unsuccessful, then the mounting stress is too great to reinstall.
Flow indicator increases negatively when flow increases
The flow direction of the sensor is opposite to the flow direction indicated by the housing, and the signal line is reversed.
Change the mounting direction and change the signal line connection.
When the fluid flows, the flow shows positive and negative jerk, the jerk range is large and sometimes the negative value is maintained
1. The AC/DC shielded wire grounding is greater than 4Ω.
2. Pipeline vibration.
3. The fluid has gas-liquid two-phase components.
4. There is a strong magnetic field or radio frequency interference around the transmitter.
1. Ground again.
2. Change the connecting pipe to the flow meter to the metal hose connection.
3. Make a hole in the pipe above the flowmeter and install a valve to discharge the gas phase components.
4. Change the environment around the transmitter.
8 ultrasonic flowmeter
phenomenon
the reason
Treatment measures
Flow rate shows drastic changes in data
The sensor is installed in places where the pipeline is vibrating or it is installed downstream of the regulating valve, pump, and orifice.
Mount the sensor away from vibrations or move upstream of the changing flow device.
The sensor is good but the flow rate is low or there is no flow rate
1. Paint and rust are not removed from the pipe.
2. The surface of the pipe is uneven or installed at the weld seam.
3. The coupling between the sensor and the pipeline is not good, the coupling surface has gaps or bubbles.
4. The sensor mounted on the sleeve weakens the ultrasonic signal.
1. Clear the pipe again and install the sensor.
2. Mount the sensor with the pipe flat or away from the weld.
3. Reinstall the couplant.
4. Move the sensor to the unsleeved pipe section.
Incorrect reading
1. The sensor is mounted on the top and bottom of the horizontal pipe, and the sediment interferes with the ultrasonic signal.
2. The sensor is mounted on a pipe with water flowing down and the pipe is not filled with fluid.
1. Install the sensor on both sides of the pipe.
2. Install the sensor on a fluid-filled pipe section.
The flowmeter works normally and suddenly the flowmeter no longer measures flow
1. The measured medium changes.
2. The measured medium is gasified due to excessive temperature.
3. The temperature of the measured medium exceeds the limit temperature of the sensor.
4. The couplant under the sensor is aging or depleted.
5. Due to high frequency interference, the meter exceeds its own filter value.
6. Number of computers
It is lost.
7. Computer crashes.
1. Change the measurement method.
2. Cool down.
3. Cool down.
4. Recoat the coupling agent.
5. Keep away from sources of interference.
6. Enter the value again.
7. Restart the meter
Computer.
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