Troxler 3430 - Page 60

4-12
EXAMPLE
Given the following values:
Bottom Density (DB) = 135 pcf (2162 kg/m
3
)
Overlay Thickness = 1.2 inches (30 mm)
DT =
K (from Table 4-1) = 0.38235
Density read by gauge (WD) = 142.0 pcf (2275 kg/m
3
)
142.0 – (135 × 0.38235)
1 – 0.38235
DT = 146.3 pcf
or,
DT =
2275 – (2162 × 0.38235)
1 – 0.38235
DT = 2345 kg/m
3
NOTE
The majority of the backscattered gamma rays reaching
the detectors are the result of interactions in the top 3.3
inches (84 mm) of the overlay. In applications where the
overlay thickness is greater than 3.3 inches (84 mm), use
(0) for the k value or use the actual gauge readings
(WD).