Innovation & Science
The use of digital radiography in health care
The long-term conservation of value and the maintenance of instruments and equipment in hospitals is an indispensable elementary condition for maintaining and restoring people's health.
Those responsible for the technical maintenance of hospital equipment have to keep it functioning with ever smaller budgets. Any likely failure of the appliances must be recognized early enough so that the components which need to be replaced can be ordered in good time. Even components which at first glance may not look impressive can be very important in this context. A potential failure of cooling or heating water pipes is no direct danger, but it can negatively affect the functioning of much more important components and in the worst case lead to the breakdown of complete systems.
Early detection systems
The company VAMED KMB which is responsible for maintenance and repairs at the Vienna General Hospital is continuously on the lookout for methods or inspection systems which can detect damage very early. Corrosion damage on the outside of insulated cold water pipes is particularly difficult to detect and can have far-reaching consequences. The early detection system desired should be capable of locating and evaluating quantitatively corrosions on the surface of pipes without the need to break the vapour barrier which would otherwise be unavoidable. The Division for Material and Welding Technology of TÜV Austria suggested the use of digital radiography. This innovative process used industrially in Austria by TÜV Austria since 2001 allows the examination of pipe sections which might be affected without the need of first removing the existing vapour barrier or insulation.
The experts of TÜV Austria can look back on many years of experience and more than 5 000 examinations performed and evaluated when applying and interpreting the results. An Ir 192 - isotope radiator is used as radiation source like for the classical radiographic examination with film technology, but instead of an X-ray film phosphorus memory foils are being exposed. The information on the phosphorus memory foils is then digitalized with a laser scanner and transformed into an analyzable image via a PC and the appropriate software. The position and size of any existing corrosions can now be measured (see illustration 1 and 2).
The suitability of digital radiography as a monitoring instrument for determining the state of corrosion was confirmed through previous trial pictures and subsequent visual assessment and verification by the Technical Test and Research Institute of TU Vienna (TVFA).
VAMED KMB then selected representative pipe sections for further examination or analysis by means of digital radiography. Although the evaluation of the pictures indicated sporadically a need for action, it confirmed that the pipe sections examined were in a tenable state as a whole, as had been expected.
Planable and conserving resources
The cooperation with the company VAMED KMB described above also shows clearly the necessary procedure for the use of digital radiography. The operator of the plant must first define the necessity or the problem exactly. Where it appears necessary this can be followed by a process evaluation in the form of reference pictures with subsequent verification of the results through alternative inspection methods.
Finally the operator of the plant in cooperation with TÜV Austria selects the spots for inspection with regard to the necessity (know-how of the operator) and the feasibility (know-how of TÜV Austria). The advantages of the use of digital radiography for the operator of the plant are obvious. Pipes or fittings can be checked without damaging the vapour barrier or insulation during operation.
There is no need any longer for switching off components or the entire plant, removing the insulation, emptying, restauration of the vapour barrier or insulation and re-commissioning, which all cost time and money. In the case of recurring inspections at regular intervals it is even possible to document damage mechanisms in relation to time and to use the results for optimizing the process.
Targeted use
It must however be emphasized that digital radiography is no substitute for the classical radiation inspection (e.g. weld seam testing), but should rather be seen as supplement or additional instrument of non-destructive testing, with the detection of corrosions, erosions and operational damage to components as its main field of application.
Autoren:
Ing. Gerd Kunes
and
Ing. Günter Balas sen.