Phased Array Ultrasonic Testing (PAUT) is ALS’s answer to maintaining the integrity of Tubular Dragline Booms and providing superior inspection confidence.
Many dragline boom designs, including the BE 1370, are made up of tubular structures. This boom is formed of tubular main chords running along the length of the boom interconnected by lacings. At nodes on the boom, as many as five intersecting lacings can join in complex welded cluster joints. These cluster joints are high stress areas and are susceptible to fatigue cracking overtime.
This cracking typically initiates within the main welded joints between the lacings and main chords. The highly cyclic loading on the boom causes cracks to propagate initially into the main chords and lacings.
Given this cracking vulnerability, cluster joints require frequent inspection as part of an overall preventative maintenance program. With draglines continually functioning 365 days a year, these cluster joints pose significant productivity threats if improperly maintained, and if not detected in time, catastrophic failure may occur.
Traditional Approach: Visual Inspection
In efforts to inspect and managed cluster cracking, visual inspection has been the accepted method for tubular dragline inspections. These visual inspections require high frequency – typically occurring on a four-week rotation and are conducted by inspectors from walkways.
Yet visual inspection is not without limitations, specifically in relation to access and visualisation restrictions. Given cluster cracking is often located in the main chord below the lacings, visual inspection fails to provide clarity on the true severity of visible defects.
The ALS Approach: Phased Array Ultrasonic Testing (PAUT)
With superior inspection confidence in mind, ALS have developed an automated PAUT scanning solution to supplement or replace visual inspection. The PAUT scanning technique ALS has developed can identify cracking in the main chord under clusters. The accuracy of the technique allows cracks to be identified early and with confidence. The extent of weld repairs can be minimised, keeping the chord parent material intact and reducing the risk and severity of damage if cracking re-emerges.
The technique can be implemented on maintenance days for routine monitoring, or during shutdowns to accurately identify any boom repair requirements. Cracks found in-service that cannot be repaired immediately can be further monitored visually for propagation using ALS’s Drone Inspection capability. Automated PAUT scanning dramatically reduces undiagnosed cluster cracking within chords, and in turn, dramatically reduces the risks associated with operating aging draglines.