Field case study · Tooele County, UT
Mobile welding boom crack repair — Tooele County, UT
Structural crack in excavator boom arm repaired onsite at a Tooele County mining site.
Reported symptom
Visual crack discovered on the underside of the boom arm near the pivot pin boss during a routine greasing. Crack was approximately 4 inches long and actively growing.
Diagnostic finding
Stress fatigue crack caused by repetitive loading in severe digging conditions. The crack originated at a weld toe and propagated along the heat-affected zone.
Repair scope
Ground out the crack to sound metal using a die grinder. Pre-heated the area with a propane torch to prevent hydrogen embrittlement. Laigned multi-pass weld using 7018 rod. Post-weld ground smooth and applied magnetic particle inspection to confirm no remaining defects.
Reported result
Boom returned to full service. Crack repair passed MPI inspection with no indications. Excavator was back on the dig face within 24 hours. Estimated $12,000 saved vs. boom replacement.
What this case helps clarify
This job is a useful example of why the first reported symptom is only the starting point. The machine type, brand, location, operating conditions, and observed diagnostic finding all shape the repair path. A similar complaint on another model may require a different test sequence or a different field-versus-shop decision.
For a new service request, send the machine make and model, hours if known, warning codes or dashboard photos, the conditions that trigger the problem, and the safest access point at the jobsite. That information helps the technician prepare the right tools and determine whether the work can be performed where the machine sits.
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