Inspect boom, arm and attachment welds at every daily walkaround after transport or impact, and give the high-stress areas a close inspection every 500 hours: welds at the boom-to-stick pivot lugs, cylinder lugs, the boom foot, bucket linkage mounts and any previous repair. Look for hairline cracks at weld toes, rust weeping from a weld line, and paint that has flaked in a straight line. Cracks at weld toes caught early are ground out and rewelded; cracks that cross a weld or spread into base metal are stop-work faults until a qualified repair is made.
How to confirm it
- Walk the boom and arm clean and dry
Dirt hides cracks, and water-filled cracks show as rust before they show as gaps. Inspect after washing, in daylight, with the machine parked and the implement grounded.
- Follow the weld toes with a light
Run your eye along every weld toe at the pivot lugs, cylinder lugs and gussets. You are looking for a fine line crossing the weld, rust weeping from the weld line, or paint flaked in a crisp straight edge.
- Clean and probe any suspect line
Wire-brush the area and drag a scraper across. A scratch in paint skids; a crack catches. Dye penetrant settles it when the eye cannot.
- Classify what you found
Hairline at a weld toe and stable: plan the repair. Crossing into base metal, at a lug, at the boom foot, or grown since last check: stop work and arrange a structural repair.
- Measure and photograph before repair
Photograph the crack with a scale beside it, and note the hours. The photo set becomes the baseline the next inspection is judged against, and it also settles warranty and insurance questions cleanly.
- Verify the repair, then keep watching it
After rewelding, inspect the repaired weld at the same 500-hour rhythm as the rest. Repairs have their own fatigue life, and the ones that get watched are the ones that hold.
What to do about it
Hairline weld-toe cracks, stable between inspections: grind out and reweld within weeks, by a qualified structural welder, and re-inspect on schedule. Do not weld over the surface without grinding the crack out; a weld laid over a crack seals the evidence and keeps the defect.
Cracks at cylinder lugs or the boom foot: stop work. These carry the highest loads on the machine, and failure there is dangerous and expensive. Repair under engineering guidance, with dye penetrant verification, before returning to service.
Elongated pin holes and worn bushings alongside cracks: the wear is the cause, the crack the symptom. Replace bushings and pins, repair the crack, and the combination holds; repair the crack alone and it returns.
Repeated cracking at the same location: the load path has changed. Review the attachments being run, the operator technique, and whether a reinforcement plate designed for that machine model should be fitted.
When a boom or arm is past repair, replacement is a normal parts transaction. Guangzhou Shenyue Machinery Technology Co., Ltd. quotes booms, arms, lugs and bushing sets by grade, stating genuine, OEM-quality or aftermarket on each line.
Need the parts this covers?
Send the machine model, serial number and the part numbers you need. We confirm fitment before payment and state the grade of every line — genuine, OEM-quality or aftermarket.
Request a quoteFrequently asked
How urgent is a small crack at a weld toe?
Urgent enough to plan, calm enough to schedule. A stable hairline at a weld toe typically has weeks of margin, and that margin is exactly what a planned repair uses. What it must not receive is months of hard work and forgetting, because fatigue cracks grow faster as they get longer.
Can my workshop weld a boom crack itself?
A workshop with a qualified structural welder, the right electrodes and preheat discipline can, and many do. What is not a repair is an over-the-top weld by the nearest torch. Grinding out to sound metal, drilling the crack tip and using penetrant verification are what separate a repair from a delay.
Do I need to drain anything or relieve anything before inspecting?
Ground the implement, shut the engine off, cycle the controls to release residual pressure, and support any raised member mechanically. Inspection itself touches nothing hydraulic, but a boom that comes down during an inspection makes the inspection memorable for the wrong reasons.