NDT X-Ray Testing
Weld X-ray Testing
Geometric unsharpness is the fuzziness of the permanent image on film or digital image. The easiest way to observe this is to take a flash light and place it over your hand with your hand 2 inches away from a table and the flash light at 12 inches away. Then move your hand to eight inch from the table keeping the flashlight pointed at your hand, and notice how fuzzy the shadow becomes. This simple exercise will make it clear that you want your x-ray source (x-ray tube, Gamma ray source) away from the part and the part to be in intimate contact with your film (object to film distance) in order to reduce geometric unsharpness. Another crucial factor in geometric unsharpness is the size of the x-ray source. You can observe this principle with a focusing flash light such as a maglight. The more focused you make the light or the smaller the actual light producing area the sharper the image will become.
Film may be processed manually or automatically with a film processor just like camera film. The film itself is a very critical part of the process. Just like photographic film speeds x-ray film speed affect the quality of the image. The slower the film and the finer the grains on the film the better the image. A good radiographer is capable of selecting the appropriate film and shot time to achieve a desired definition, sensitivity and resolution of the image they will also be capable of ensuring that the film meets a specific Class and be artifact, scratch and crimp mark free. Each film manufacturer has their own Film Speed. The most common Film manufacturers for NDT Radiography testing in the U.S. are Fuji and Agfa you may click on each of the links for information on their film speed and classifications.
NDT Training and Services X-ray films are often augmented by filters and screens. These filters and screen reduce scatter radiation, intensify and can take away from the image when used improperly. Most codes specify the thickness of intensifying screens required for a specific energy of radiation. The thicknesses are determined by the amount of intensification or absorption which the screens provide for the specific energy.
Industrial radiography is quickly being replaced by phased array ultrasonic nondestructive testing and GPR Ground penetration radar. Phased array is a safe alternative with adequate material penetration and internal mapping capabilities allowing the inspector to pinpoint the exact internal location of flaws without having to clear the area of people. So imagine doing an inspection in a busy office building. If you could use ultrasound or GPR and let everyone work around you; would you? or would you choose to clear three floors of people to take an x-ray shot.
Work Around Industrial Radiographers
When working around industrial radiographers your safety is important. The most important thing to observe is to ensure that you obey the yellow and magenta ropes and the radiation signs to keep yourself in the safe zone (low radiation zone). The x-ray technicians should have attended a radiation safety course and state requirements require the ropes and signs. Obey them for your safety. We strongly recommend keeping children and pregnant woman completely away from the area. If you are near industrial radiographers and they do not have the restricted/radiation area roped off I would contact your safety representative and have them ask questions.
X-Ray Technicians Safety
X-ray Technicians keep themselves safe by keeping distance between themselves and the X-ray generation device which they are using. If you observe a technician they should have a film badge attached to their bodies usually on the waist or chest and a small tubular item called a dosimeter in their pocket or attached to their body. The other safety item that they use is a small handheld radiation detection device called a survey meter. If they are working with a live source they will also be wearing a little metal box on their hips called an alarm rate meter. All of these items are required to keep the inspectors and the public safe. The survey meter measures radiation rate or how much radiation the technician would get if he stood in that one spot for one hour. The film badge records absorbed radiation dose by the inspector and gets sent out for processing on a monthly basis to make sure the individual has not been accidentally exposed to radiation throughout the month. The Dosimeter is read at the end of the day for a radiation Roentgen measurement received that day and the alarm rate measures in absorbed dose rate and is designed to make a loud piercing sound if you are in a very dangerous radiation area.
If you are a quality assurance manager or a company outsourcing NDT you should ensure that the facility providing your services has not reduced code requirements. You can ensure this by requesting the personnel records of the technician doing the work and verifying them with the applicable standard. This is a normal practice and on request the contractor should provide you with the information fairly quickly. If they do not, you should question their services and perhaps hire a third party ASNT Level III to provide an onsite audit of their facility. Common mistakes found on certification paperwork include not enough training or experience hours, training facility and person that provided the training not listed, and method or technique not listed.
NDT Level III PT, MT, ET, UT, RT, VT