Fault analysis of pyrology 3370EX fluorescence spe

2022-08-16
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Failure analysis and treatment of RIKEN 3370e X-ray fluorescence spectrum analyzer

3370ex fluorescence spectrum analyzer is a product of Japan RIKEN Corporation in the late 1980s. It is mainly used to analyze the chemical composition of steel, alloy, various mineral products, slag, chemical products, food, agricultural products, biology and environmental protection samples. The instrument was introduced into our hospital in 1989 and has been used for more than ten years. During its operation, some faults have occurred successively. Now several circuit faults and treatment methods are introduced as follows:

1 high voltage generator fault

1.1 fault phenomenon

Press 7 Please read the instructions carefully and start the machine according to the normal procedure. When the high voltage of the X-ray tube is gradually increased, the instrument gives a snort. At the same time, it is observed that the voltmeter and current on the control panel of the high voltage generator are all zero, and the X-ray indicator light is off, indicating that there is no high voltage output from the high voltage generator

1.2 fault analysis

immediately turn off the power supply of the high-voltage generator and the main power supply of the instrument. Open the control box of the high-voltage generator, visually check and find that the fuse F1 of the main circuit is burnt out, and detect and determine the open circuit of the fuse. The working principle of the main circuit of the high-voltage generator is that the output voltage can be adjusted by changing the conduction angle of the thyristor K1 and K2. The boosting process must be carried out step by step with a certain time interval. The reasons for the overcurrent protection action of the fuse are analyzed as follows:

A) the error code of the control signal output by the control circuit is wrong, resulting in the sudden full conduction of the thyristor

b) sudden short-circuit damage of silicon can be controlled, which is similar to sudden full conduction

c) internal components of high voltage generator are damaged and short circuit occurs

d) X-ray tube is broken and short circuit occurs

after inspection and test, the control signal output by the control circuit is correct, the thyristors K1 and K2 are intact, the X-ray tube is intact, and no abnormality is found at the input end of the high-voltage transformer box. There should be a problem inside the high-voltage transformer box

1.3 troubleshooting

the high-voltage transformer box is a high-voltage transformer immersed in the high-voltage transformer oil, a high-voltage rectifier filter, a filament power supply and a measuring circuit

first remove the high-voltage cable, power line and control line, and remove the high-voltage transformer box from the instrument; Then open the box cover and take out the high-voltage transformer and rectifier filter circuit; When the oil dries slightly, check the devices one by one, find out the short circuit of the high-voltage filter capacitor, and determine that the cause of the fault is the damage of the high-voltage capacitor. Replace with a new high-voltage capacitor, restore the rectifier filter circuit and high-voltage transformer box, put it back into the instrument, connect the connecting cable, and replace with a new fuse F1. Check and confirm that there is no error, turn on the power supply of the instrument and the high-voltage generator, set the high-voltage step by step, and the rated value of the voltmeter is correct. The high-voltage generator was repaired and the instrument returned to normal operation

it should be noted that special attention should be paid in this maintenance work: (1) after turning off the power supply, when disassembling the high-voltage generator, it is necessary to wait for a period of time to fully discharge the high-voltage circuit to ensure safety; (2) The transformer needs to be tested for performance. If it is unqualified, it must be replaced; (3) The high-voltage transformer and rectifier filter circuit should be slowly put back into the oil, and bubbles should be avoided as far as possible to reduce the insulation performance of the oil

2 fault of cleaning f-pc counter center wire

2.1 fault phenomenon

f-pc counter center wire cleaning process: when f-pc counter center is cleaned, the instrument sends an alarm message: there is no cleaning current. Then do PAH (pulse height analyzer) adjustment, and the f-pc counter does not count. Check the f-pc counter and find that the center wire is seriously over-current and burnt out

2.2 fault analysis

f-pc counter center wire cleaning process: f-pc counter rotates to the cleaning position, the center wire is connected to the cleaning circuit through the contact piece, and the cleaning current is automatically controlled to be connected, and it is maintained for a certain time, so that the center wire is heated to a higher temperature, and the pollutants on its surface are burned to achieve the purpose of cleaning. According to the original analysis of f-pc counter center wire cleaning circuit, the possible causes of center wire failure are:

A) current limiting resistance R is damaged

b) the cleaning voltage is too high

c) there is a problem with the time control circuit, and the power on time is too long

because the burning of the central wire is caused by overcurrent, it tends to cause a and B. Actual inspection; The current limiting resistance R, cleaning voltage and time control circuits are normal. Therefore, the dynamic inspection is carried out, and the resistance to ground of the contact point is 0 when the central wire is turned to the cleaning position. If the above problems can be solved at this time, adding the rated cleaning voltage will inevitably cause the center wire to burn out due to overcurrent; However, there is no current through the current limiting resistor R, so there is no cleaning current for the instrument alarm. It is found that the contact piece of the cleaning position is loose. When the contact on the counter is pressed, it will be in short contact with the wall of the spectroscopic chamber. It needs to be connected to the baby's nose, mouth or vein, causing wire burning failure. Fasten the contact piece, reinstall the center wire, and install the f-pc counter. After power on inspection, the automatic cleaning function of the f-pc counter center wire of the instrument is normal

3 heating circuit failure

3.1 therefore, it is understood that the failure phenomenon

the instrument starts normally, the data is abnormal when doing standardization, the temperature is lower than normal when touching the instrument shell, check the heating circuit, and find that the heater is not heated, and the fan does not turn

3.2 fault analysis

the internal temperature of the instrument is controlled at 371 ℃, and its heating circuit principle. The voltage between the test points is 200V AC (the power supply of the instrument is Japanese standard), and at this time, the fan does not rotate, which should be the fan is broken. Observe that the heating indicator light D is on, indicating that there is a heating signal. The voltage between the detection points is 200V AC, indicating that the driving part works normally. Further check that the temperature fuse resistance Rt is open and the heater is in good condition. The analysis shows that due to long-term operation, the fan is damaged, causing the heater to overheat, making the temperature protection resistance Rt act, disconnecting the heating circuit and stopping the heater

3.3 troubleshooting

replace the fan and temperature fuse resistor. Restart the machine, and the fan and heater work normally

4 vacuum detection circuit fault

4.1 fault phenomenon

start the machine according to the correct degree. Because the vacuum degree of the analysis room is always stable at a certain value, it cannot reach the required value, and the instrument stagnates in the vacuum pumping state of power on self-test, so it cannot enter the normal working state

4.2 fault analysis and treatment

first, check the sealing of all joints of the vacuum system, and there is no problem. Secondly, check the vacuum detection circuit. Using the same characteristics of the vacuum detection circuit in the analysis room and the sample room, exchange the vacuum detection circuit and the detector respectively for inspection. When the same state is found, the vacuum of the analysis chamber and the measured value of the output of the detection circuit are low. Therefore, without knowing the circuit parameters, the voltage and electrical parameters of the circuit are tested by comparison in sections, and finally the problem point is found, and the device with poor performance: electrolytic capacitor is found. Due to the decrease of insulation and the increase of leakage, the potential at this point is low, resulting in the vacuum measurement value lower than the actual value. After replacing the device, the power on self-test passed smoothly, and the instrument returned to normal operation

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