Ultrasonic NDT

Effective Thermal Fatigue Cracking Characterization in Pipeline Branch Connections

Published on 23rd November 2020

Effective Thermal Fatigue Cracking Characterization in Pipeline Branch Connections

Source: Effective Thermal Fatigue Cracking Characterization in Pipeline Branch Connections (eddyfi.com)

Ensuring the smooth operation of pipelines responsible for transporting contents throughout different areas of a process plant depends on regular assessment of the pipework including all branch connections. Because pipelines and other factory components are exposed to cyclic thermal stresses like those incurred from extreme temperatures or condensate and steam system contact, they are more susceptible to fatigue cracking. To maximize productivity in an economy that demands efficiency, Non-Intrusive Inspection (NII) is necessary to determine Fitness-For-Service (FFS) of these online assets.

The Challenge

Deliver better data results from examination of the typically difficult-to-access inside surface of branch connections.


Thermal Fatigue Cracking

Thermal fatigue cracking, or TFAT, damage is a real threat to branch connections, and conventional A-scan ultrasonic techniques are the current NII method for detecting this defect. The traditional Non-Destructive Testing (NDT)approach uses a tangential ultrasonic technique with a conventional search unit to locate the bore of the main pipe, the crotch corner area of the bore, and the bore of the branch pipe. An operator uses an array of single angle probes to locate cracking emanating from the regions of interest. Although this technique has proven to be successful in detecting damage, the geometry of certain branch connections adds complexity to this inspection region and can restrict full coverage. Furthermore, accurate sizing of damage can be difficult.


Overview of the typical inspection area


Inspection coverage of a typical branch connection

The Solution

Phased array ultrasonic testing technology improves upon current non-intrusive methods of inspection.


Sectorial scan from 0/180 position with phased array response


Tangential scanning showing phased array response with no reflectors present