Here are some common faults of CT tubes sorted out for everyone
(1) Faults in high-voltage control circuits and high-voltage cables: including aging and oxidation of joints, poor contact, reduced insulation, overvoltage, undervoltage or breakdown that causes high voltage, short circuit of high-voltage transformers, and sparking or breakdown of high-voltage capacitors. This leads to a decline in imaging performance, an increase in snowflakes, image artifacts, and even the inability to form images.(2) Filament circuit failure: The uniformity of filament emission drops, the number of snowflake dots in the image increases, or the filament melts and opens the circuit, there is high-voltage tube current or large current fluctuation, resulting in no radiation and a marbled image. The reason is that the service life has ended and the filament has aged. In an emergency, it is advisable to consider swapping the circuits of the large and small filaments and adjusting the working parameters.
(3) Faults with the rotating anode: It does not rotate or rotates at a low speed, and the high-speed bearing makes a lot of noise. The reasons are: first, the rotating anode bearing is worn or there is too much debris on the target surface that gets stuck; second, the stator coil is open-circuited or there is a short circuit between turns inside, and there are faults with the rotating controller and inverter trigger.
(4) High-pressure sparking: It is divided into sparking inside the tube sleeve and sparking inside the tube core.
A. Sparking inside the pipe sleeve is caused by bubbles inside the pipe sleeve or A decline in the insulation properties of the insulating oil or local insulating materials within the pipe sleeve. The presence of bubbles inside the tube sleeve is due to the fact that the internal temperature of the ball tube is very high during operation, reaching up to 3000 degrees in an instant. Above c, the insulating oil inside the tube sleeve expands and contracts due to heat and cold, and the volume contraction of the insulating oil and the adjustment of the air bag inside the ball tube. If the oil circuit seal ages or loses its elasticity, air will enter and form bubbles. When the bubbles are small, a sparking sound can be heard. When the bubbles are large, the machine will stop and report overload.
B. The spark inside the die is caused by the drop in the vacuum degree of the die. The vacuum degree drop of the tube core is usually caused by reasons such as the tube being stored for too long, the release of various materials inside the tube core, the tube being frequently used under overload conditions, or poor manufacturing of the tube core. A drop in the vacuum degree of the die will cause overload, fail to expose or trip the high-voltage circuit breaker.
(5) Faults in the detection circuits for temperature and humidity control, high voltage kV, filament current mA, etc.
(6) Malfunction of the cooling circulation system: The oil pump or fan wears out and fails due to long-term operation, the temperature and pressure sensors malfunction, the switch gives false alarms, the heat exchanger is contaminated and affects the heat dissipation efficiency, and the heat cannot be distributed in time, causing the glass tube to overheat, contract and crack.
The general service life of a CT tube is 100,000 to 200,000 times. If it is carefully maintained, its lifespan can be increased by 50%. Therefore, the daily maintenance of CT tubes is of vital importance.
(1) Regularly check whether the oil circulation of the tubes is normal and clean the dust on the heat sinks regularly.
(2) Regularly test and monitor the power supply status, the phase and phase amplitude balance and stability of the three-phase power supply, no phase shift, the resistance value of the ground wire, whether the grounding is good, and the voltage must not exceed 15% of the rated value. The contact between the high-voltage cable and the hose should be good. Ensure that the silicone pad and high-voltage silicone grease of the high-voltage cable plug are intact and there are no impurities in the contact parts.
(3) Regularly test various working parameters of the tube, mainly including the correction and maintenance of tube current, tube voltage, exposure time, and overload protection installation. Do not exceed the anode heat capacity or heat dissipation ratio, and avoid overloading.
(4) Develop maintenance plans, keep records of maintenance work, and establish files for troubleshooting.