The development of the rotating anode X-ray tube greatly improved the quality of diagnostic images; however, it also brought along the challenge of accepting a certain level of noise.The rotating anode design requires the use of ball bearings to support the assembly and required tolerances in order to maintain an accurate focal spot. X-ray tube anodes rotate at a speed of approximately 9,000 RPM, which results in an audible sound. Bearings used in conventional applications, such as a car, are lubricated with oil or grease, allowing them to run smoothly and quietly. Due to internal construction constraints, typical lubricants are not usual in X-ray tubes. Instead, a thin coating of metal, typically lead or silver, is used as a lubricant. Silver coatings can withstand higher temperatures, but are not as quiet at lead coatings. The thickness and composition of the lubricant has a direct effect on the sound.Noise is also dependent on the tube position. The mechanical structure of the bearing assembly results in placing pressure in different directions as the X-ray tube is rotated. In the case of CT scanners, gantry rotational speed will also change the bearing pressure and resulting sound.
It is important to note that a change in the noise level typically does not affect tube quality or life. In some instances, a tube may initially have a higher sound level, then quiet down after a few weeks of use. If you notice the noise continuously increasing in level or pitch, then service may soon be required.
Our Technical Support Team is available 24 x 7 at 800.238.3780 to answer any further questions you may have.