DR Brings Dual Energy Detection to the NDT Maintenance Field
By Ron Pincu, Ofra Kleinberger and Rachel Lieberman, Vidisco Ltd.
As stated earlier, the Security field has brought several of its substantial DR achievements to the NDT field including rapid setup, portability, excellent image quality, high POD, environmental friendliness and immediate imaging. One outstanding example is the current use of Dual Energy in NDT.
Vidisco originally introduced Dual Energy in its portable form to the world of Security X-ray in 2004. The essence of this technology is to differentiate between organic substances (indicated in orange coloring) and inorganic substances (light inorganic materials such as glass are shown in green hues, while hard inorganic materials such as metals are indicated in shades of blue). This differentiation is enabled by taking X-ray images at various energy levels (at least two, hence the name “Dual Energy”), and comparing density in order to deduct if a material seen in an X-ray image is organic or inorganic. This technology is used in every modern airport today in order to detect explosives and drugs, which can be traced as organic substances.
Vidisco brought this technology even further by enabling detection of organic material behind a metal external layer using the “probe function.”
Dual Energy X-ray of RPG: Before (left) and After (right) "Probe"
A common type of NDT inspection is the use of DR to detect water penetration in honeycomb structures. Water, which freezes and expands in high altitudes, causes separation of the structure, which leads to instability and lack of durability of the airborne aircraft. Following the detection of water in the damaged area, the “skin” is punctured in order to evaporate or drain the water. In the next stage, the damaged area is sealed with one of several types of epoxy, some organic and others inorganic. A repeat X-ray examination is then conducted to ensure no water remains in the repaired parts.
A problem arises in repeat assessments: In most cases the epoxy’s density is very similar to that of water. Thus, it is difficult to conclude whether the material being viewed is epoxy or water.
To resolve this problem, Vidisco has developed an algorithm based on Dual Energy techniques which is capable of distinguishing between water and a wide range of epoxy sealants. In the X-ray image, water clearly shows up in red (see image below), enabling differentiation between water and sealants.
The accumulation of over 20 years of experience and research in the area of Security Digital X-ray has produced top-quality devices initially developed for specific security needs. These devices and tools have already contributed significantly to several areas of NDT Digital radiography.
The X-ray inspection industry (both Security and NDT) is rapidly shifting towards DR and Portable DR. Today, the exchange of know-how and data is becoming increasingly reciprocal between the two fields. There is no doubt that the extensive expertise acquired in the area of security, with the constant competition between inspectors and hostile factors creating ever rising demands and appropriate responses respectively, can and will make even greater contributions in the future.
Water in dual energy