After we complete the visual inspection of our welds to make sure that everything looks right, we use an ultrasonic testing machine that can give us an internal image of the steel so that we can get a more thorough image of everything.
Welding machines basically heat the steel and melt a stick of aluminum or other metal which will fill the gap between the pieces of steel. When everything cools off and solidifies, you should be left with a solid connection between the two pieces where the gap is completely filled in.
It is possible to occasionally get an air bubble or have a place where the metals have a weak contact point. If this is on the inside of the weld, then we won’t be able to see it during the visual inspection so this is why we want to use the ultrasonic testing machine to give us an image of the internal sections of the steel and the welds.
The ultrasonic testers work by sending ultrasonic sound waves through the metal and measuring the waves as they are bounced back. The machine can then take the readings and convert them to a visual display that we can easily read. If there are any air bubbles or imperfections in the metal then we will be able to see exactly where they are and how big they are so that we can decide if we need to go back and redo the weld.
In the video, you can see that there is a gel that is being applied to the steel tubes. This acts as a contact agent for the machine and without it, the sound waves would be immediately reflected off of the surface instead of penetrating through the steel. This is just for the inspection process and it is removed before the process of sandblasting and sealing the steel.
Weak or broken welds could be catastrophic for the structural strength of the SeaPod base so we always ensure to test every weld thoroughly. If all of the welds pass the testing with the ultrasonic machine then that means that they are sufficient to be used in the structure that will hold the weight of the SeaPod for years to come while it is floating at sea.