Ultrasonic Oil Tank Testing
By John Nolan On January 25, 2017
I've been made fun of several times while performing these tests. "So John, is my tank having a boy or a girl?" After all, when most people hear the word ultrasound, they think of pregnancies, newborn health, doctor's offices, and the like. But ultrasonic technology is used in a variety of other industries: automotive, aerospace, metallurgy, and welding to name a few. So what does that mean to you, the home buyer/owner/seller? In order to answer that question effectively, there is prerequite knowledge I must explain first.
What Is Ultrasonic Testing?
Ultrasonic 
testing is a non-destructive test that uses (you guessed it!) sound waves. These waves are propagated through materials to test for internal flaws and to determine specific properties. Most often these materials are metals, but wood, concrete, and composite materials may also be tested this way.
How It Works
The principle behind ultrasound is similar to that of sonar. During an ultrasound, a transducer emits a pulse into the object being inspected. This pulse moves through the material until in encounters a change in density. This change could be the result of an internal defect or the pulse simply reaching the material's back wall. In either case, the pulse gets reflected back and the time elapsed between emission and arrival of the pulse's "echo" is used to calculate the thickness of the material at that spot. If the calculated thickness value does not agree with the expected value, then an internal imperfection has been found.
Principle of ultrasonic testing. LEFT: A probe sends a sound wave into a test material. There are two indications, one from the initial pulse of the probe, and the second due to the back wall echo. RIGHT: A defect creates a third indication and simultaneously reduces the amplitude of the back wall indication. The depth of the defect is determined by the ratio D/EpCredit: Wikipedia
Testing Fuel Oil Tanks
Fuel 
oil tanks corrode from within. This corrosion is most often the result of condensation and sludge inside the tank, both of which sink to the bottom. Since you can't see the tank rusting, there is little to no warning when the rust finally penetrates through to the outside. When that happens, there is little time to react before a leak develops and the contents of the tank are now on your basement floor causing a huge mess and costing thousands in cleanup. Using an ultrasonic transmitter, we test the thickness of the walls of the tank at dozens of points so see if they have worn thin from corrosion.
