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Guidance for performing
Dock Inspection and
Underwater Ultrasonic Thickness Surveys
When performing dock inspection using ultrasonics, readings should be made on cleaned metal free of rust. If a clean hard coating exists, readings may be taken through the coating without damaging it. It is as important that the diver observe the steel conditions, as it is that the instrument man observe the readings recorded. A reading taken on or near a severely pitted or holed surface should indicate as such. The diver should look for suspect areas and corrosion cells easily visible by their color. Pitted surfaces should be measure. Mud line readings should be taken slightly below the surface of the bottom 6 inches to 12 inches into the silt. If a corrosion pattern exists, attempt to comment on it at the site.
The severest corrosion generally exists at the top of the steel structure and just below the low water line. Attempt to establish the low water line at the beginning of inspection. Keys to finding this are:
- Knowing the tide range and measuring down from the high water mark stains.
- Cross bracing and fasteners are generally located as close as possible to low water (12 inches above).
- Heavy marine growth quite often begins at low water.
- Check for a tide board
At the completion of an inspection, immediately record observation and comments.
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phone 973-616-4501, fax 973-616-4501, email info@pcaengineering.com, web www.pcaengineering.com
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