Diagnosis method for common faults of the hottest

2022-07-23
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Diagnostic methods for common faults of sequential X-ray fluorescence spectrometer

in the future, the environmental protection policy of titanium dioxide industry will continue to be tightened. The spectrometer is a scanning instrument. When the instrument is running, many components are moving, such as goniometer, crystal converter, collimator, etc. the frequently moving components are prone to problems. In addition, the electronic circuit board that controls and detects the action of each component may also have problems

the new X-ray fluorescence spectrometer is equipped with fault diagnosis software. The sensors distributed in each part of the instrument transmit the status signal of the instrument to the computer for the instrument operator and maintenance engineer to judge whether the instrument is normal and find the fault location However, some problems in the measurement process can not be found by the diagnostic software, and the diagnostic software only prompts the occurrence of the fault. To find the cause of the fault, the maintenance personnel are required to be familiar with the structure of the instrument and have some maintenance experience This paper introduces the causes and treatment methods of five common faults

1 fault symptom 1

x-ray generator high voltage cannot be switched on

fault analysis:

this is a common fault of the X-ray fluorescence spectrometer. It usually occurs when the instrument is turned on and occasionally occurs when the instrument is running The causes of faults can be analyzed from three aspects: 1. X-ray protection system; 2. Internal water circulating cooling system; 3. High voltage generator and X-ray tube

1.1 X-ray protection system

in order to prevent X-ray leakage, the high-voltage generator can only be started when the X-ray protection system is normal Whether the ray protection system is normal or not, mainly check the following two parts:

1, clarify the division of labor and whether the position of the time schedule requirements panel is normal Metal also has its shortcomings. The X-ray fluorescence spectrometer is a closed system, and the panel is the outermost ray protection device. If one panel is not in place, the instrument may leak rays Therefore, there is a position contact sensor on each panel. The panel is not fully closed and the high voltage cannot be opened

2, whether the X-ray warning signs are normal The national standard [1] stipulates that the X-ray fluorescence spectrometer must be equipped with a red warning signal lamp and linked with the corresponding switch. Therefore, if the signal lamp fails, the high voltage cannot be turned on

there is a simple method to judge whether the failure of high voltage startup is caused by the ray protection system, that is, set the instrument status to maintenance status and shield the ray protection system. If the high voltage can be turned on at this time, it can be determined that the failure is caused by the problem of the ray protection system

1.2 internal water circulating cooling system

the output power of the high-voltage generator is generally 3KW or 4kw. After the high pressure is added to the X-ray tube, except for a small part used to generate x-rays, most of it is converted into heat energy and taken away by the internal water circulating cooling system The internal circulating water is used to cool the light tube head near the anode target. Therefore, the internal circulating water is required to be deionized water with very low conductivity to prevent high-voltage breakdown The conductivity of the internal circulating water is reduced through the deionized resin column inside the instrument. The resin in the deionized resin column will be invalid for a long time. Therefore, when the high pressure cannot be started, check the conductivity of the internal circulating water. If the conductivity cannot be reduced, consider replacing the resin In addition, the water level of internal circulating water is too low, which will also cause the high pressure to fail to open

there is also a fault phenomenon that the high pressure switches on for a few minutes and then jumps off. The cause of this fault may be that the flow of internal circulating water is too small The flow of internal circulating water is measured by the flowmeter, and the water flows through the flowmeter to drive the impeller in the flowmeter. The impeller cuts the magnetic line of force and generates an electrical signal If the impeller rotates in the water for a long time, it may be rusted, which will slow down the rotation speed of the impeller and weaken the electrical signal of the flowmeter, so that the instrument mistakenly believes that the water flow is too small, resulting in high-pressure tripping In addition, the filtration blockage of internal circulating water will reduce the water flow and cause high-pressure tripping

1.3 high voltage generator and X-ray tube itself

high voltage generator and X-ray tube are the most valuable components in the instrument, and generally will not cause problems Check the high-voltage generator. Open the high-voltage generator. According to the circuit diagram, check whether each switch is in the normal position, and check whether the fuse is blown. Further inspection is best done by a professional maintenance engineer The X-ray tube is a closed part. Once it is damaged, it can only be replaced, not repaired Check the X-ray tube to check whether the connection between the X-ray tube and the high-voltage cable is normal and whether the high-voltage cable is damaged

2 fault phenomenon 2

the vacuum in the spectrum chamber and the sample chamber fails to reach the specified value

fault analysis:

x-ray fluorescence spectrometry usually works under the condition of vacuum light path, but many parts of the spectrum chamber and sample chamber are connected to the outside, and many parts may leak When checking the vacuum fault, artificially divide the possible problems into three parts: vacuum pump, sample room and spectrum room. Check these three parts one by one to narrow the scope

2.1 vacuum pump

remove the interface between the vacuum pump and the spectrum chamber and the sample chamber, plug it with a rubber stopper, and then vacuum. If the specified value can be reached within a few seconds, the possibility of failure of the vacuum pump can be eliminated If the specified value can be pumped for a long time, the efficiency of the vacuum pump may be reduced. This usually happens on the instrument that often analyzes the tablet pressing samples and oil products. The powder or oil is sucked into the vacuum pump oil, which changes the viscosity of the oil. At this time, the vacuum pump oil needs to be replaced

2.2 sample chamber

the most common air leakage position in the sample chamber is the sealing ring on the sample rotation device. The sample usually rotates at the speed of 0.5 RPM during measurement. After several years of operation, the sealing ring at the sample rotation is worn and the sealing effect becomes worse

2.3 spectrum room

the most common air leakage position in the spectrum room is the gas flow counter. The gas flow counter is installed in the spectrum room. There is an air inlet pipe and an air outlet pipe connected with the outside world. The window film of the gas flow counter is very thin. If the window film leaks, the vacuum of the spectrum room will be affected Inspection method: connect the air inlet pipe and air outlet pipe with a hose to isolate the air flow counter from the outside, and then vacuum

check the vacuum fault. During disassembly and installation, be careful not to let ash or hair fall on the sealing ring to avoid new air leakage points. During installation, apply a little vacuum grease on the sealing part

3 fault symptom III

the counting rate is unstable

fault analysis:

x-ray fluorescence spectrometer has two common detectors: flow counter and scintillation counter The scintillation counter is very stable, and the problem often occurs on the gas flow counter

the window film of the gas flow counter is composed of a piece of polyester film, HOSTAPHAN film or polypropylene film coated with a very thin (about 30nm) aluminum film. As the window film bears atmospheric pressure, after a period of time, with the extension of the matrix material, the aluminum film may crack, thus weakening the conductivity. This situation has little effect on the pulse height distribution, but will make the counting rate unstable New models of X-ray fluorescence spectrometers are generally installed with 1 m or even 0.6 m window film instead of 6 m window film. Therefore, it is more likely that the conductivity of the window film of the flow counter will decrease

inspection method [2]: under the condition of low X-ray tube power, select a sample with a k k counting rate of about 2000cps, measure the counting rate, then replace the original sample with a sample with high potassium content, adjust the light tube to full power, keep it for 2 minutes, then reduce the X-ray tube power to the original value, measure the first sample, if the window film conductivity is normal, the original counting rate will be obtained, if the window film conductivity becomes poor, the counting rate will be found to be reduced, and then slowly rise to the initial value, At this time, the window membrane should be replaced

4 fault phenomenon 4

2 during scanning, it is found that the peak shape is not smooth and there are small sawtooth shapes

fault analysis:

crystal is the most vulnerable component in the instrument. Try not to touch the diffraction surface with your hands. If your hands or other things touch the diffraction surface of the crystal, it will pollute the crystal. Sweat or other substances on your hands will seep into the surface of the crystal, changing the lattice spacing on the surface of the crystal. However, X-ray fluorescence diffraction mainly occurs on the surface of the crystal, so the peak shape of 2-scan is not smooth It is difficult to eliminate this kind of fault at the moment. Reference [3] introduces the surface treatment method of the crystal by querying the data of No. 18, but it is generally not clean

5 fault phenomenon V

2 only noise signal appears during scanning, and there is no peak position signal

fault analysis:

there are two possible reasons:

5.1 the preamplifier circuit of the detector is faulty, and the noise signal is circuit noise, not X-ray signal

5.2 the and 2 coupling relationship of the goniometer is confused. Usually, the data in the CMOS controlling the and 2 coupling relationship is lost due to battery leakage and other reasons. At this time, it is necessary to re align the light

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