Non-Destructive Testing: Answering The Call To Underwater Inspection

The Golden Gate Bridge is 1.7 miles long and carries about 112,000 vehicles per day.

A small crack in the bridge could have devastating effects.

But thanks to the invention of NDT, or Non-Destructive Testing, divers are able to identify small defects in structures and equipment of all sizes to ensure their integrity..

Small Defects, Major Problems

For years, one of the greatest hazards that underwater structures faced was that a single component failure could lead to a catastrophic collapse.

Failures in ship structures, offshore platforms, propulsion systems, or any other kind of equipment failure can and have resulted in the loss of equipment and life.

Non Destructive Testing (NDT) Equipment and Tools

Prefabricated Ships: Not The Ship For War

One notable example was the prefabricated Liberty transport ships of the 1940s. These ships were the backbone of the war effort since they were so quick and easy to construct. The fastest, Liberty Ship, SS Robert E. Peary, was built in an incredible 4 days, 15 hours, 29 minutes.

However, there was a problem with mass producing ships in this way. Of the 2,710 Liberty Ships built, a total of 12 ships broke in half due to brittle tiny fractures that arose from the quality of in the steel used in the manufacturing process.

This resulted in a major loss of ships, cargo, and sailors.

All of which could have been prevented with the use of modern NDT techniques.

Saving Lives: Non-Destructive Testing

Nondestructive testing (NDT) involves using a range of analysis techniques to test materials for structural damage or weaknesses.

NDT testing at DIT

Nondestructive testing is used during the manufacturing process and fabrication of a component. NDT is also used at regular intervals during the component’s service life to check for any structural weaknesses that will affect reliability.

Main Types of Non-Destructive Testing

There are lots of different NDT techniques, the most common types are as follows:

  • Visual testing
  • Radiographic testing
  • Ultrasonic testing
  • Eddy-current testing
  • Dye Penetrant

Let’s take a look at a few of these in more detail:

Visual inspection is the most common form of underwater NDT. It involves divers specially trained in NDT visually checking components for damage, cracks, or signs of fatigue. While it might be a cost-effective way of detecting larger problems, visual inspection is not able to detect small or internal structural problems.

Radiographic testing involves using either X-rays or gamma rays to identify problems. These forms of electromagnetic radiation pass through a material and are detected when they come out the other side. Any abnormality in the metal composition is immediately detectable via variations in the results. Radiographic inspection is particularly useful in accessing weld grades.

Ultrasonic testing works in much the same way as radiographic testing. This technique involves using an ultrasound transducer, which is linked to a diagnostic machine, to pass ultrasonic waves through a material to access its composition.

Eddy current testing uses electromagnetic induction, which is the creation of an electromotive force or voltage across a conductor within a changing magnetic field, to detect faults in a metal. It is particularly useful as it doesn’t require a piece of metal to be cleaned before being tested.

Advantages of NDT

There are a number of key advantages to nondestructive testing:

  • Doesn’t damage or require the component to be dismantled for testing
  • Cheap
  • Fast
  • Very accurate

The biggest advantage out of all these points is that NDT doesn’t require the destruction of the component being tested.

Without NDT, then oil companies, would have to completely deconstruct entire rigs in order to test structural components. With around 1,000 offshore oil rigs globally, this would be an extremely costly thing to do.

NDT Education: Divers School Of Technology Provides World-Class Training

Not just anyone can perform nondestructive testing. It is a field that requires highly trained individuals. Commercial divers will need to learn how to use a range of new equipment as well as understand the processes by which they operate.

NDT in DIT’s classroom

All NDT divers should be well trained in using transducers, magnetic yokes, ultrasonic gauges, pit gauges, and cameras etc. These are essential tools in nondestructive testing and so must be operated properly.

After all, who wants a sunken ship or a collapsed oil rig on their conscience, right?

NDT Training For Rookies

While not all commercial diving schools include NDT testing as standard in their core courses, some do.

The Seattle based Divers Institute Of Technology (DIT) covers many aspects of NDT testing in their core commercial diving course.

Certification For Veteran Divers

For those divers that wish to make this field their specialty, or to increase their skill set to make themselves more appealing to employers, DIT also has dedicated standalone courses too.

Level I Liquid Penetrant Testing 4-hour Initial Training Certificate


Level II Magnetic Particle Testing 20-hour Initial Training Certificate

These courses provide students with all the practical knowledge and qualifications they will need to perform “basic NDT inspections in various sectors of the industry”.

NDT testing at DIT

In this training, students are not only taught how to undertake all the main types of non-destruction tests but also how to write reports so that they conform with the specifications required by law.

Throughout the course, students will be taught the relevant guidelines and terminology they need to use to get it right.

So bring plenty of paper!

Do It, But Do It Right

Regardless of whether your just now looking into commercial diving, or your a veteran diver looking to boost your career, a well-trained NDT diver is going to up your job opportunities and increase the numbers in your bank account.

So make sure your getting an education that will help you confidently land one of the jobs!

DIT is a school you can count on to help get you the job of your dreams.

Aran Davis, Writer for Water Welders

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