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The maintenance procedures of Electromagnetic flow meter
Dec 17, 2018

The maintenance procedures of Electromagnetic flowmeter 


1 General

1.1 Subject content and practical scope

This regulation specifies the specific technical requirements and implementation procedures for the maintenance, overhaul, commissioning and safety precautions of electromagnetic flowmeters.

This procedure is applicable to the 3000 electromagnetic flowmeter (hereinafter referred to as the instrument) used in the chemical equipment online. Other instruments of the same type should also be used as reference.

1.2 basic working principle

The meter works on the principle of electromagnetic induction.

1.3 composition and function shown in Figure 1.

The meter consists of two parts: the sensor and the converter. The sensor will change the liquid flow signal into an induced electromotive force that is a function of it. The converter converts the potential signal (mV) from the sensor into a uniform 4-20mADC signal and displays the flow by the digital panel.

1.4 Main technical performance and specifications

1.4.1 Performance Indicators

Basic error ±0.5%

1.4.2 Specifications

Flow rate range: 0.3~1.0m/s to 1.0~9.999m/s

Output signal: 4 ~ 20mA

Power supply: 100 ~ 120VAC

Ambient humidity: & not; 10 ~ 50 ° C

Relative humidity: 40% to 80%

Liquid conductivity: 300μS/m

Pulse output: 0 ~ 17HZ

Scale range: 0 ~ 4m & sup3;

Pipe diameter: 25mm, 50mm, 100mm

1.5 Basic requirements for maintenance personnel

a. Maintenance personnel should have the following conditions:

b. Familiar with the relevant technical documents such as this regulation and the corresponding product manual;

c. Understand the process flow and the role of the instrument in it;

d. Master the basic theoretical knowledge of the opposite aspects of electrical engineering, electronic technology, chemical measurement instruments and maintenance;

e. Master the basic functions of maintenance, overhaul, commissioning and common fault handling of the instrument;

f. Master the use of commonly used test instruments and related standard instruments.

The maintenance procedures of Electromagnetic flowmeter

2 Good condition

2.1 Complete parts and meet technical requirements. which is:

a. The brand name should be cleaned correctly;

b. Parts should be complete and standardized;

c. Fasteners shall not be loose;

d. The connector should be in good contact;

e. Terminal wiring should be secure;

f. The seal should be free of leaks;

h. The protection and insulation facilities are intact;

2.2 The normal operation meets the requirements, namely:

a. When operating, the meter should meet the specified performance indicators;

b. Under normal working conditions, the instrument should indicate that the value should be more than one third of the full scale.

2.3 The equipment and environment are neat, clean and meet the working requirements, namely:

a. The whole machine should be clean, free of rust, the paint layer should be smooth, bright, and not falling off;

b. The scale should be clear and the font should be regular;

c. The instrument line should be laid neatly;

d. The line label should be complete, clear and accurate.

2.4 The technical information is complete and accurate, and meets the management requirements, namely:

a. The specification, certificate of conformity, and certificate of entry into the factory shall be complete;

b. Operation records, fault handling records, maintenance records, calibration records, and parts replacement records shall be accurate;

c. The system schematic diagram and wiring diagram should be complete and accurate;

d. The meter constant and its change record should be complete and accurate.

3 Maintenance

3.1 Routine maintenance

3.1.1 Circuit inspection

At least two inspections per shift, including:

a. Know the operation of the instrument to the on-duty process personnel;

b. Check if the meter indication is normal;

c. Check if the power supply of the instrument is normal;

d. Check the watch body (connecting pipes, lines) for leaks, damage, and corrosion;

e. Identify problems and deal with them in a timely manner.

3.1.2 Regular maintenance

Regular maintenance includes:

a. Maintenance records of each class's operation;

b. Perform instrument cleaning once a week;

c. Perform a damping check on the operation of the instrument once a month;

d. Perform instrument zero calibration every three months;

e. Perform sensor electrode cleaning every six months.

3.2 Regular calibration

3.2.1 Calibration cycle

The calibration cycle is 12

3.2.2 Calibration instrument

Calibrated tributary ammeter: 0 ~ 30mA, 0.1 level

Standard AC ammeter: 0 ~ 50mA, 0.1 level

Precision digital voltmeter: 4 digits

Precision resistor: 1Ω, 0.1

Oscilloscope

3.2.3 Calibration wiring

Calibration wiring is shown in Figure 2.

3.2.4 Conversion Zero Adjustment

Turn on the meter power supply, preheat for 10 minutes, then fill the sensor pipeline with water. At this time, the current value should be 4mA. Otherwise, adjust the zero potentiometer so that the current indication is 4mA, and the meter LED is displayed as “0.00”.

3.2.5 Damping adjustment

When the output fluctuates, the damping trimmer capacitor can be adjusted, and the damping time constant can be selected between 1 and 10 seconds.

3.2.6 Sensor excitation current adjustment

The sensor excitation current adjustment wiring is shown in Figure 3.

Observe the waveform on the oscilloscope. The positive and negative directions should be symmetrical, otherwise check it. Then remove the 1Ω resistor and adjust the excitation current to trim the capacitor so that the current is 24mA.

3.2.7 full-scale flow rate setting

Find the instrument constant K according to the maximum flow rate and the instrument flow path: UFS=A•K

 Where: UFS—the meter passes the maximum flow rate;

A—the flow diameter of the instrument;

K-constant

With the range setting switch UFS value, the meter can work according to the set range.

3.2.8 Calibration quality standards

The calibrated meter shall meet the performance specifications specified in 1.4.1.

3.3 Troubleshooting

Symptom Cause Remedy

Indicates that the overrange circuit is open in the negative direction, the terminal is loose or the power is off. Check the terminal block, power supply.

There is no measured medium in the measuring pipeline. Check the pipeline for medium, so that the pipeline is filled with process medium.

The electrode is covered by an insulator. The cleaning electrode

Indicates that there is a sword in the liquid containing high conductivity in the liquid. Use 5 seconds to attenuate or

Electrode has a cleaning electrode

Indication of irregular changes, the electrode is completely insulated, cleaning the electrode

Large fluid flow pulsation

Electrode leaks liquid, detector is damp

Make the insulation between the electrode and the ground low. Disassemble the cleaning electrode and dry the electrode.

The maintenance procedures of Electromagnetic flowmeter

4 Overhaul

4.1 Maintenance cycle

The instrument is serviced every 12 months and is usually synchronized with the annual overhaul of the plant.

4.2 Repair content

4.2.1 Remove contaminants and oxides from the fuse tubes and sockets.

4.2.2 Remove the dust inside the converter.

4.2.3 Check the contact condition of each connector to ensure reliable contact.

4.2.4 Clean the sensor electrodes.

4.2.5 Calibrate the meter in accordance with Article 3.2 of the Articles of Association.

4.2.6 The instrument after inspection shall be verified according to the national (department) measurement verification procedures.

4.3 Maintenance quality standards

The instrument after inspection shall meet the conditions as stipulated in Chapter 2.

5 Commissioning

5.1 Preparation before commissioning

5.1.1 Check if the power supply of the instrument is normal.

5.1.2 Check if the pressure pipe joint of the instrument is firm.

5.1.3 Check whether the setting parameters of the instrument are correct.

5.2 commissioning steps

5.2.1 Turn on the meter power.

5.2.2 Preheat for 15 minutes.

5.2.3 When the pipe is filled with a stationary liquid, the digital display should show “0.00%” and the output current is 4 mA.

5.2.4 If the flow rate shows large fluctuations, adjust the damping to make it stable.

5.3 Acceptance

5.3.1 Check the completion of the maintenance items one by one.

5.3.2 Check whether the instrument meets the quality standards for maintenance.

5.2.3 After the instrument has been in normal operation for 72 hours, it will be signed by the relevant technical supervisor.

6 Safety precautions

6.1 Maintenance Safety Precautions

6.1.1 Maintenance must be performed by two or more people.

6.1.2 For work that can cause fluctuations in process parameters, prior approval must be obtained from the process personnel.

6.1.3 After the sensor is repaired, lock the cover to prevent the instrument from getting wet.

6.2 Inspection safety precautions

6.2.1 Inspection and repair work tickets must be handled for the maintenance of the operating instrument.

6.2.2 Do not take electricity or pressure to disassemble the instrument.

6.2.3 Do not use unsuitable tools to prevent damage to instrument components.

6.2.4 Unqualified parts are not allowed to be used.

6.2.5 When cleaning instrument parts and printed circuit boards, a suitable cleaning agent must be used.

6.2.6 The sensor should be discharged and relieved before disassembly.

6.3 Operation safety precautions

6.3.1 The operation must be performed by two or more people.

6.3.2 Before the operation, it is necessary to contact the craftsman and obtain the assistance and cooperation of the craftsman.

6.3.3 After the instrument is put into operation, the operation of the instrument and the related process parameters should be closely monitored. After confirming the normal operation of the instrument, the operation can be considered completed.