mmchugh2,
Are you speaking of a UT thickness inspection or weld inspection? Since there is liquid not air on the opposite side of the tank wall, you will not get 100% reflection of the ultrasound. In a thickness inspection the result is the return echo will be of diminished amplitude. The lower signal may not trigger a digital thickness gage to produce a reading. 'brimmer' is correct that the liquid will not affect the accuracy of the readings but a full a-scan instrument may be needed to trigger on the lower amplitude signal. If you are doing a weld inspection, particulary using angle beam, calibration points beyond half node will be invaled. As mentioned above, a portion of the sound will couple into the liquid. Unless a similar sitaution is present on the calibration block, calibration reflector reflections from the calibration block will be non-conservative. Angle beam inspections should be limited to half node.
JR97