Used Excavator Boom and Stick Crack & Weld Inspection Guide

Structural inspection map

Used Excavator Boom and Stick Crack & Weld Inspection Guide

Pause the purchase when there is an active crack, undocumented structural welding or visible misalignment. Uniform paint does not prove the boom and stick are original.

Six zones that concentrate the evidence

Used excavator for boom and stick structural inspection
Representative inventory image. All six zones require close-up evidence from the exact machine.
A

Boom foot

Inspect frame welds, ears, pins and plate transitions. Look for lines returning through paint, trapped rust and lateral movement.

B

Cylinder mounts

Compare both sides of ears, gussets and beads. Tearing often begins where thickness changes or a repair terminates.

C

Boom knuckle and box

Use raking light on all four faces. Compare symmetry, rippling, added plates, weld ends and deformation.

D

Stick base and nose

Inspect the boom pin, bucket-cylinder base and bucket-pin housing. Measure pin play as a separate issue.

E

Linkage and coupler

Check cracks, rotated bushes, locks, hooks and coupler welds. Confirm that the locking system is compatible.

F

Previous repairs

Do not stop at the visible plate: follow bead ends, reinforcement edges and the opposite face. Request before/during/after images.

Separate wear, repair and an active crack

Finding What to compare Next decision
Cracked paint without a metal line May be rigid coating over a flexing area. Clean locally and use raking light; do not conclude from paint alone.
Fine rust emerging from a line Raises concern about repeated opening and closing. Remove load, clean and escalate to testing by competent personnel.
Weld bead differs from opposite side May be repair, fabrication or modification. Compare geometry, factory references, procedure and records.
Reinforcement plate with sharp corners May concentrate stress at the reinforcement end. Inspect perimeter and reverse face; request engineering procedure.
Rippling or displaced stick Suggests deformation, heat or previous loading. Measure alignment through pins and bucket; paint is not the remedy.
Uniform weld with records Reduces uncertainty but alone does not prove capacity. Verify material, process, final inspection and functional test.

Field sequence: non-invasive first, specialist when justified

  1. 1

    Clean without erasing

    Remove mud and grease from critical zones and photograph before abrasion. Do not polish away traceability.

  2. 2

    Comparative visual check

    Use raking light and compare left/right side, colour, texture, bead, thickness and symmetry.

  3. 3

    Functional observation

    With a competent operator and clear zone, watch flex, sound and movement during slow cycles and after warm-up.

  4. 4

    Dimensional record

    Record play, alignment, gap and location on a marked image. Do not apply one generic limit to every model.

  5. 5

    Specialist testing

    When evidence warrants it, a qualified inspector chooses dye penetrant, magnetic particle or ultrasonic testing for material and defect.

  6. 6

    Documented decision

    Classify original/no finding, documented repair, pending finding or unacceptable defect; attach evidence to the order.

Minimum record for a structural repair

  • Exact machine identity and marked damage location.
  • Before, during and after photographs with date and scale.
  • Base/filler material, preparation, preheat and sequence.
  • Repairer identity or qualification and procedure used.
  • Non-destructive test result where applicable.
  • Dimensional check, loaded function test and later follow-up.

Official sources behind the method

Boom, stick and weld questions

Does every non-original weld mean reject?

No. An identified repair performed to a compatible procedure, inspected and aligned can be evaluated. Hidden or undocumented work should be priced as risk.

Is dye penetrant always the right test?

No. Suitability depends on material, preparation and flaw type. Competent personnel must select and perform testing; penetrant does not replace engineering assessment.

Does repainting remove the evidence?

It may hide colour and corrosion temporarily, but changes in bead, thickness, symmetry and deformation often remain visible under light and comparison.

Where do cracks usually start?

Transitions, cylinder mounts, reinforcement ends, pin housings and old repairs deserve priority, but the entire structure still needs inspection.

Can photographs support the final decision?

They can screen risk, not finish the assessment. Structural decisions need local cleaning, physical inspection, measurement, load observation and specialist testing when indicated.

What belongs in the quotation?

Describe every repair as documented, pending verification or unacceptable, with location, images and allowance for inspection or correction.

Published and reviewed: 19 August 2026 · YUANJIAN MACHINERY INTERNATIONAL TRADING LIMITED