High-energy piping (HEP) systems operate at extreme pressures and temperatures where a number of damage mechanisms can cause wall thinning, cracking, material degradation or other component failures. To avoid a catastrophe, the timely detection of damage caused by high-temperature creep, fatigue, creep-fatigue, thermal shock, ratcheting or flow-accelerated corrosion is necessary.
HEP presents particular challenges for risk management because its structural complexity often makes the inspection process a challenge.
Ultrasonic shear wave testing was the inspection standard for decades until linear phased array (LPA) came out. However, early-stage creep damage is not detectable in these components with conventional ultrasonics, time-of-flight diffraction (TOFD) or LPA. The current capabilities of LPA and TOFD can only detect late-stage creep when it has progressed to a crack. This equates to approximately 85 percent expended life of the system, or 15 percent or less remaining life.
Only annular phased array (APA) and segmented annular matrix phased array (MPA) have proven the ability to detect early- stage creep damage.
Segmented annular MPA versus APA
APA was introduced to the market in the 1990s. The probe consists of concentric rings of elements capable of 2-D focusing to a small spot as well as detecting aligned cavitation. The beam angle is fixed by the angle of the wedge, which means it cannot sweep through multiple angles like LPA. Consequently, the APA system must employ a skip-scan method, where scans across the weld are performed at discrete locations around the circumference or along the length, which results in less than 10-percent coverage per weld, typically less than 5 percent of the length. APA is not capable of inspecting an entire weld. Thus, this technique is not intended for a single-line manual scan, as multiple scans are needed to be merged into one image to detect creep. The limited coverage misses large lengths of the weld, which may contain emerging creep damage.
Segmented annular MPA builds upon the advancements of APA and LPA, combining the best aspects of both inspection methods. TEAM Industrial Services' proprietary MPA system can scan 100 percent of the accessible length of girth and long-seam welds to detect early-stage creep damage wherever it occurs along the length of a weld. As with APA, this system can detect aligned cavitation and heavily clustered isolated cavitations. 2-D focusing is achieved with a 128-element matrix probe. The MPA beam angle can sweep between 30-80 degrees, enabling the scan to be performed along the entire axis weld. As a result, TEAM's MPA system is capable of detecting creep twice as early as LPA or TOFD, increasing the detection at approximately 70-percent expended life, or 30-percent remaining life. This early-stage detection doubles the amount of time needed between inspections, reducing overall inspection costs.
TEAM also offers an engineering assessment through Quest Integrity to rank the welds to determine those with the highest risk of developing creep damage. This allows the inspection to be performed on fewer welds while still determining if the system is experiencing early- stage creep damage.
For more information, visit www. TeamInc.com or call (800) 662-8326. â¢
