Why X-Ray Tubes Fail

X-ray tubes are subject to significant thermal and electrical stress throughout their operating life. The cathode assembly can reach temperatures of approximately 450°C, while the anode may reach about 1100°C. Repeated heating and cooling cycles gradually affect the insert, insulating materials and cooling system.

Insulating oil performs two important functions: high-voltage insulation and heat removal from the insert. Over time, exposure to high temperatures can degrade the oil and reduce its dielectric properties, increasing the risk of high-voltage instability.

Vacuum conditions inside the insert can also deteriorate with age. Thermal cycling of metal-glass seals and other joints, together with the release of residual gases from internal materials, can increase gas pressure inside the insert. This may result in unstable tube operation and high-voltage arcs or spits.

Another important ageing mechanism is the gradual evaporation of material from the anode and cathode. Conductive material can be deposited on internal insulating surfaces, reducing their ability to withstand high voltage and eventually contributing to arc discharges.

X-ray tubes rarely fail without warning. Changes in tube behaviour, recurring arcs or spits, emission problems and information contained in CT error logs can provide early indications of developing problems. Identifying these signs in time may allow the tube to be evaluated and, in some cases, repaired before complete failure.