QotW: How do container scanners work?
Julia Ravey set out to address this scanner snag from listener Alaster: "The electricals in my car stopped working after it was transported from Cape Town to the UK. I think there was a fault in the scanner in Cape Town. My question is, how does a car scanner work? Can it damage the electrical components within cars?"
Julia - An interesting question. If your car was transported overseas, then it would’ve been done through a shipping cargo scanner at the port. So how do those scanners work? Here with us is Roger Worrall from the security company Westminster Group PLC who has a few points to help us understand how these scanners work.
Roger - The scanners used to scan the contents of cargo containers are X-ray scanners, meaning we can compare them to the scanners used in airports. Your hand baggage is sent through an X-Ray baggage scanner which have two x-ray generators, typically 180 kV each. Your hand luggage can contain your mobile phone, camera, laptop, iPad, Kindle which all go through the scanner unaffected. Your hold luggage goes through a larger size physical size X-Ray scanner or a CT scanner, again there is no effect to electronic devices.
Julia - X-ray scanners work by sending out X-rays from a generator, towards the object inside. These rays are then absorbed at different rates depending on the materials within the object. A detector on the other side then picks up the X-rays that aren’t absorbed and displays the image based on the radiation that passed through.
Roger - Sea freight containers are X-Ray scanned using a 6 Mev or a 7.5 Mev x-ray generator, that’s over 33,000 times more volts than the airport hand luggage scanners mentioned earlier. And yet in these cargo containers, electronic devices should still receive no damage.
Julia - That’s because the increase in power doesn’t affect the wavelength of an X-ray. X-rays have a very short wavelength, which is what allows them to travel between molecules.
Roger - When scanning a whole vehicle, the driver first leaves the vehicle and the scanning system runs on rails and passes over the truck cab and container. Mobile Scanners extend an arm out that contains the x-ray receivers, the driver then drives the arm over cars, trucks and containers to see what’s inside.
Julia - So Alaster, it seems that the scanner may not be the cause of the electrical faults in the cars. X-rays aren’t designed to affect electronic equipment. We do hope you’re able to find the answers for how this happened to your car in the insurance investigation. Next week, we’re figuring out this function of fridges, from listener Josie
Josie - Why can't I immediately open my fridge door after closing it? It feels like air pressure is keeping it closed. Is this the case?