Men, I searched and searched...to no avail. Does anyone have any input on performing UT on storage tanks that are full of liquids? Specifically, water, fuel oil and sulfuric acid.
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.
This is solely for the purpose of gathering thickness data on walls. The tanks have been in service for many years and are part of a continuous process. The cost and trouble involved in emptying these tanks would be borderline absurd simply for the purpose of UT. We have a required internal inspection at a given time frame with UT readings required at the midpoint of that time.
Are these tanks pressurized? If so then they will most likely need to be proof tested and then wall thickness inspected and NDT inspected for defects.
If not required, then the above comments are correct. UT wall check wont be affected with liquids internally.
These are very common inspections that should be no problem for the avarage NDE outfit...if they can deal with a rental but the bigger ones like Team Industrial or Acuren would provide you with a tank crawler Link with a probe on it that feeds back readings to the UT set below. Typically 4 points or 8 if requested up each course to the top angle. The great thing is its a continuous scan and areas of interest could be investigated on the fly but this is of course dependent on your surface condition and you may need to settle for spot readings.
The crawler can also be used on cone roofs(and yes some old riveted ones too) with an unknown thickness to get some data feedback if it's safe for access if any additional UT would be requested later on. Finish up with UT nozzle necks, chine thickness points, bottom shell 12" scan points. This obviously already includes a full visual inspection and a settlement survey could also be done in a day with a two man crew.
![[evil]](/data/assets/smilies/evil.gif "[evil] [evil]")
Does anyone have any input on performing UT on storage tanks that are full of liquids? Specifically, water, fuel oil and sulfuric acid.