X-Ray Diffraction (XRD) systems analyze the structure of materials such as crystals and powders. The X-Ray Tube generates heat from the interaction of electrons in the cathode and the anode. The electrons emitted from the cathode (filament) are accelerated towards the anode – when the electrons hit the anode, they produce x-rays. Keep in mind that the focal “spot” on the anode is most commonly only 12×0.4mm rectangular. The full power of the generator is being dissipated in this tiny surface area. Without the built-in safety systems of the XRD machine, were the heat generated by this process not dissipated through circulated water cooling, the X-Ray Tube and the XRD system would certainly sustain damage. Consequently, water flow and cooling performance are critical to a healthy XRD system.
Water Cooling System Issues
The following are four main issues to watch out for:
1. Water leaks – Water leaks occur as a result of loose, damaged, or improperly connected water lines. Not only can water leaks cause damage to the X-Ray tube, but they can also damage other XRD system electronic components.
2. Insufficient water flow – When the water flow rate is too low, this can result in the overheating of the X-Ray tube, subsequently dropping the intensity of the X-Ray beam. Because the machine is constantly monitoring rate of flow, this issue results in water flow alarms and disruption of the XRD analysis.
3. Inconsistent water flow – Variance or inconsistency in water flow can lead to temperature fluctuation in the X-Ray tube. This can affect the quality of the x-ray beam and the integrity of the collected XRD data, especially in high-resolution applications.
4. Blockages in the water circuit – Blockages occur when there is a buildup of particulates (mineral buildup or debris) which reduce or completely block water flow. Again, this can reduce or block water flow resulting in flow rate faults and disruption to the operation of the XRD system.
Components to Inspect and Replace
To prevent water flow issues, it is critical to regularly maintain and inspect the water cooling system to ensure ongoing peak performance. As part of every annual Preventive Maintenance Service performed by KS Analytical Systems, the following components are inspected and replaced:
-Tube Stand O-Rings: The X-Ray tube stand secures/holds the X-Ray tube and isolates the x-ray emissions when the shutter is closed. As part of the cooling system, the tube stand contains several water pathways and connections to circulate water through the X-Ray tube to prevent overheating. The O-Rings are seals installed around the water connections to prevent leaks and achieve a tight fit between the tube stand and water connections. Over time, these O-rings can become brittle or misshapen (flattened out / warped). Whenever the X-Ray tube is removed, we always recommend inspecting these O-Rings.
-Water Flow Sensor O-Rings: The water flow sensor monitors the water flow of the XRD cooling system, plays a crucial role in the redundant safety systems of the machine, and supports consistent accuracy and reliability of the XRD data. The XRD system is programmed to alert the operator and shut down X-Ray generation in the event of a water flow rate reduction below a safe threshold–below roughly 3.6 liters per minute (some machines have a two-stage shut down process / some go into standby mode). Note that the target threshold rate of water flow is 4 liters per minute or above. Much like the tube stand O-Rings, over time these O-Rings can deteriorate / become brittle which can result in failure. Also, during the process of replacing the impeller wheel bushings (located inside of the water flow sensor) these O-Rings are very susceptible to damage when opening / installing the cover of the sensor. Like the other components on this list, we recommend replacing the Water Flow Sensor O-Rings annually.
-Water Flow Sensor Impeller Wheel Bushings: The Water Flow Sensor Impeller Wheel Bushings consist of two small components that are installed over the shafts of the impeller wheel. These bushings are very important to the rotation of the impeller wheel, and allow a smooth and frictionless rotation. Over time, these bushings can wear out due to the constant rotation of the impeller wheel as well as exposure to water and other particulates/contaminates. If the impeller wheel stops rotating smoothly, this can result in inaccurate readings from the water flow sensor, leading to overheating and potential damage to the X-Ray tube. We recommend replacing these bushings as-needed during PM service.
We Are Here to Help!
KS Analytical Systems provides full support for Siemens and Bruker XRD / WDXRF systems, and we are here to partner with our customers to ensure their machines are achieving optimal performance. We also support laboratories and facilities with fully integrated maintenance staff. As part of this effort, we offer a PM Kit containing all of the items summarized in this post. You can find the kit, which includes a specifically-designed Water Flow Sensor Disassembly Tool, at https://store.ksanalytical.com/ . Also, for an in-depth video tutorial for Siemens and Bruker XRD water circuit troubleshooting, visit https://www.youtube.com/watch?v=kn3LnA20i0c&t=1333s . Lastly, if you have any questions or run into any issues with your XRD / XRF system, don’t hesitate to reach out directly by calling (940) 453-8786 or emailing us at ksa@ksanalytical.com . Thank you for stopping by!
