The Bolt Inspection Solution – Difference Between UT and TFM/SAFT Methods

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ABSTRACT

Bolts are widely used in every industry and their integrity is vital in ensuring that “assets remain safe during their lifetime”. Traditional methods for checking bolts normally are removing and visually inspecting, however this not only takes a long time but is also expensive. Downtime for any reason is best avoided when possible.

By utilizing the A1550 IntroVisor or A1525 Solo ultrasonic flaw detector using the TFM/SAFT technologies, bolts can be quickly and accurately inspected without the need for them to be removed, allowing the plant to continue to operate at capacity, saving time and money.

INSPECTION PROCEDURE

In this application note, our SaigonIC uses the Conventional Ultrasonic and TFM/SAFT methods on the A1550 IntroVisor to test bolt with a length of about 144 mm and 33 mm diameter with the notch positions as shown in the image below.

1. Calibration

In fact, the body of the bolt is mostly installed in other parts so their length will not be known. Therefore, we will make calibration at the edge of the bolt head as shown in the image below, and the result of sound velocity is about 5985 m/s.

The Calibration by Conventional Ultrasonic Method
The Calibration by TFM/SAFT Ultrasonic Method

2. Inspection

Usually, the junction Head-to-Shank and the Thread are the most common areas to break. Therefore, for bolt inspection, we should focus on these areas.

a. To inspection for Head-to-Shank 

The videos and images below show the difference between using conventional ultrasonic and TFM/SAFT methods.

Tested Result by Conventional Ultrasonic Method – The Defects at The Head-to-Shank can be Ignored
Tested Result by TFM Method using Multi-SAFT Technology – The Defects at The Head-to-Shank can detection quick and accuracy

b. To inspection for Thread 

The videos and images below show the difference between using conventional ultrasonic and TFM/SAFT methods.

Tested Result by Conventional Ultrasonic Method – Cannot Detection for The Shallow or was Overlap Defects at The Threads
Tested Result by TFM Method using Multi-SAFT Technology – The Defects at The Threads can almost be detected quick and accuracy

CONCLUSION

As the tested results above, we can conclude that:

  • For the UT method: It’s difficult or cannot detect shallow or was overlap defects, and the defects at the Head-to-Shank can be ignored.
  • For the TFM method using Multi-SAFT technology: It’s a quick and efficient solution to perform an inspection of bolts on site. Data can be recorded with accurate cross-section images (B-Scan), giving the ability to monitor the growth of any defects. And It will give greater accuracy in defect sizing.

Performed and Edited by SaigonIC