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Repair screening · Cracked components

Should this crack be weld repaired?

“Can we just weld it up?” is usually asked before anyone knows why the crack is there. This check screens the five things that decide whether weld repair is even a candidate: the item, the mechanism, the material, the design basis and whether quality can be verified.

Start the screeningWhat makes weld repair fail
Pathway at a glance

Weld repair pathway

A crack is not a welding problem until the mechanism, material, duty and verification route are understood.

Weld repair go/no-go — screening gates Four screening gates in sequence: unknown crack mechanism means investigate first; unknown or difficult material means a specialist pathway; failure under normal duty means redesign rather than restore; unverifiable quality means do not weld repair. Passing all gates makes weld repair a candidate to develop. Crack confirmed and mapped Is the crack mechanism known? no Investigate first NDT, evidence, root cause yes Material known and weldable? no / difficult Specialist pathway OEM input or replace yes Did it fail under normal duty? yes Redesign, not restore detail or duty problem no — one-off event Can the repair be verified? no Do not weld repair replace or temporary fix yes Weld repair candidate design, qualify, inspect, record Amber — resolve before deciding · Red — stop this pathway · Green — proceed with engineering
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How to use this summary

  • Unknown mechanism or unknown material is a stop-point: investigate first.
  • If the component cracked under normal duty, restoring it as-was usually restores the problem.
  • A repair candidate still needs crack removal, a qualified procedure, inspection and a return-to-service basis.
  • If quality cannot be achieved or verified, do not treat weld repair as the default pathway.

This screens whether pursuing a repair is defensible. It is not a repair approval.

01

Screen before committing to fabrication

The tool is intentionally conservative. It never approves a repair; it exposes whether a weld repair is worth developing or whether investigation, redesign or replacement should come first.

Risk→Item→Cause→Material→Verify
Immediate risk

Is the cracked item still in service?

This first gate is about immediate operability, not the eventual repair method.

02

What makes weld repair fail

Most bad repair decisions fail before the arc starts: the mechanism, material, design basis or verification plan was wrong.

01

Wrong mechanism

Fatigue cracks welded over without removing the cause often return at the same detail.

02

Wrong material assumption

High-carbon, cast or quenched-and-tempered materials can turn one crack into several if the weldability basis is wrong.

03

Restored inadequacy

Like-for-like restoration of a detail that cracked under normal service simply recreates the original problem.

04

Unverifiable quality

No NDT of the excavation, no qualified procedure and no records means the repair exists but the evidence does not.

03

Worked screening examples

01
Machine steelwork

Cracked mounting bracket with proposed heavier gussets

Context: The bracket cracked under normal duty and the proposed repair would change stiffness and load path.

Screening view: This screens toward redesign or modification rather than simple restoration. The new geometry needs an engineering basis.

02
Pressure equipment

Cracked air receiver nozzle weld

Context: The material is known, the mechanism can be investigated and access for repair and NDT is possible during shutdown.

Screening view: This can screen as a candidate repair, but the pressure-equipment obligations and AS/NZS 3788 / AS 3992 documentation pathway must be carried through.

03
Cranes

Cracked pick-and-carry crane boom

Context: The component is lifting equipment and may use high-strength Q&T steel, with OEM requirements and fatigue-critical geometry.

Screening view: This screens as a specialist pathway. OEM input, material confirmation and re-verification may be more important than the weld itself.

04

Reference basis

This tool points to the standards and guidance families normally considered during repair assessment. It does not reproduce clauses or replace project-specific repair design.

AS/NZS 3788In-service inspection of pressure equipment — repair assessment context
AS 3992Welding of pressure equipment — procedure qualification pathway
AS/NZS ISO 15614.1Welding procedure qualification for structural work
AS 2550 seriesCranes — safe use, inspection and repair expectations
AS 4991Lifting devices — verification after repair
Weld Australia technical guidanceRepair welding and welding quality guidance
Important limitation

This is a screening framework, not a repair approval, weld procedure or fitness-for-service assessment. Cracked plant can be an immediate hazard: operability decisions, repair design and return-to-service assessments for real equipment need project-specific engineering by a competent person — in Queensland, typically involving an RPEQ.

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