September_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | S E P T E M B E R 2 0 1 9 2 1 radioactive sources, such as securing boundary areas to minimize radiation exposure, as well as permits and regu- lations that apply in many states. The responsibility falls on the radiographer to be able to produce a quality image. The most common sources of ra- diation for gamma-ray radiography are shown in Table 2 with their respective half-lives and penetrating power [5] . The term “going hot” directly relates to the source being active during exposures. Figure 5 shows a camera that holds a radiation source. The camera is “hot” compared with the environment due to heat generation from the source. When the source is cranked out, the area is hot. RADIOGRAPHIC INSPECTION OF ELECTRICAL GENERATORS Generators can be under constant cyclic thermal and electrical stresses. The changes in grid demand coupled with required operating conditions to maximize profitability can cause strain in the internal components, which already experience vibrations, core looseness, and degradation over time. The ability to inspect components with minimal disassembly enables deter- mination of these effects in some of the critical components in the genera- tor. Additionally, degradation resulting from normal wear and tear can also be inspected during outages. Siemens Energy developed pro- cesses to inspect insulated generator components [patent pending], without the need to strip insulation from com- ponents to visually inspect them pri- or to assessing serviceability and need for repair (Fig. 6). Combinations of x-ray and gamma ray techniques were used to develop parameters necessary to complete inspection both during man- ufacturing and in short duration outag- es in the field. As with any radiographic inspec- tion, the application of these tech- niques requires the necessary safety procedures, equipment and two-sided access to create the exposures of the components inspected. The technique Fig. 5 — Thermographic image from radiation source camera showing that the camera is “hot” compared with the environment due to heat generation from the gamma-radiation source. Fig. 6 — Generator insulated end winding.