X-ray tubes are generally designed to function properly under the most demanding conditions. Where tubes for benchtop systems would not have to be replaced during the entire system lifetime, the lifespan of an X-ray tube for floor standing systems can range from 1 to 30 years. This is mainly determined by the way of use and maintenance. So, here is an overview of the main recommendations for optimal tube usage, based on X-ray tube physics.
- X-ray tubes like to be warm. In that way, the internal getter remains active and the vacuum remains good. Therefore, tubes should not be left unused for too long, in any case not for more than 6 months.
- The power supply to the tube should be steady. In addition, in standby setting, the power -and especially the emission current- should not be too high, as this costs lifetime.
- A high kV setting during standby is no problem, it helps the tube to remain stable against flashes.
- Make sure that no substance ever comes into contact with the windows, and never touch the windows under any circumstance. Not even for cleaning.
- Cooling water is always critical (chemical and physical composition, temperature, flow), as the tube at full power operates on the edge of its physical limitations (temperatures, melting points etc.).
- Cold water does not cool better than (luke) warm water. Optimum water-in temperature for tubes is 20-25 °C. In very warm and humid conditions, 25-30 °C is recommended. It is best to be always above dew point (dew point can be lowered by e.g. climate control in the surroundings).
- Tidy sample preparation is an essential processing step for good analysis anyway. On top of that, it helps to retain your tube’s lifespan.
- Regular preventive maintenance does wonders! A tube is like a car in a way: you cannot drive at top speed all the time and never pause for maintenance.
Tips for tube cooling maintenance
- Clean and uninterrupted flow of cooling water is as important as the cooling water itself. Therefore, the tube’s cooling circuit must be checked and cleaned regularly.
- Never cool with pure de-ionized water, as this is acid and chemically aggressive.
- Always make sure that the slit cooler is placed in the correct way.
- If you experience an unusually fast intensity degradation, it is almost certain that the tube is not properly cooled.
Tips for tube in on, off and standby settings
- When the tube will not be used for more than a few hours, it is advised to put it on standby settings. This saves lifetime.
- When the tube will not be used for more than 24 hours, it is advised to switch it off completely.
- When the tube is switched off completely, always switch off the water flow completely within 1-2 minutes. NEVER let the water flow for more than 2 minutes after power off. Otherwise, condensation of water inside the tube shield can occur.
- Also, NEVER switch off the water flow first (inducing an automatic power off), as this can kill the tube instantly.
Tips to enhance the stability and lifetime of the tube
Every tube is designed to be operated at its maximum power rating. Applying maximum power is absolutely no problem. There is, however, no denying that every X-ray tube will undergo physical and chemical ageing. These ageing processes are driven mainly by high temperatures and high-temperature gradients inside the tube.
- At maximum power, the physical and chemical ageing processes inside the tube go faster than at lower power. Therefore, it is advised to avoid maximum power if your application does not need it.
- Driving at 80-90% of the maximum power already has a significant positive effect on the stability and lifetime of the tube.
If you unexpectedly do need a new X-ray tube, Malvern Panalytical, being the only major analytical equipment supplier with its own tube factory, offers X-ray diffraction and X-ray fluorescence tubes, as well as X-ray tubes for industrial and non-destructive testing.