3.1 Why this is different from wear tracking
Lesson 2 covered wear — a slow, predictable thinning of the liner that you can measure and project forward. Cracks and damage behave differently: they can appear suddenly, from an impact, a manufacturing flaw, or fatigue building silently under normal operation, and once a crack starts, it can propagate fast. A liner that measured fine last month can still fail this month if a crack has been growing invisibly beneath the surface.
This is why inspection for damage is not just "more of the same wear check" — it needs different techniques, aimed at finding defects that a simple thickness reading will miss entirely.
3.2 Four types of damage to know
Abrasive wear
Gradual, even thinning from continuous particle contact. Predictable and trackable — covered in Lesson 2.
Impact damage
Chips, dents, or fractures from a tramp object (oversize rock, metal debris) striking the liner.
Corrosion
Chemical attack from the slurry's pH or dissolved chemistry, weakening or pitting the liner surface.
Fatigue cracking
Hairline cracks at welds, flanges, or stress points from repeated pressure and vibration cycles over time.
3.3 Detection techniques
A visual check catches only what's on the surface and visible from the outside. Finding hidden or early-stage damage takes methods built specifically for that purpose.
| Technique | What it finds | Notes |
|---|---|---|
| Visual inspection | Surface cracks, chips, discoloration, bulging | Fast, but misses anything beneath the surface |
| Dye penetrant testing | Fine surface cracks invisible to the naked eye | Dye seeps into cracks, then a developer makes them visible |
| Ultrasonic flaw detection | Sub-surface cracks and voids within the material | Uses sound-wave reflection, needs a trained technician |
| Tap testing | Liner debonding from the shell (hollow sound) | Simple hammer tap, listen for a dull vs. sharp response |
3.4 Red flags — stop and act immediately
Most findings can wait for the next scheduled maintenance window. A small number cannot — these mean the unit should be shut down before the shift ends, not logged for later.
- A crack that has penetrated through the full liner thickness
- Visible bulging or "ballooning" of the shell wall
- An active leak of slurry through the vessel body
- A liner section that sounds hollow across a wide area under tap testing (advanced debonding)
- Cracks and damage behave differently from wear — they can appear and propagate fast, so they need dedicated detection methods, not just a thickness reading.
- The four main damage types — abrasive wear, impact, corrosion, and fatigue cracking — each have different causes and different warning signs.
- Dye penetrant and ultrasonic flaw detection find damage a visual check alone will miss.
- A small set of findings — through-wall cracks, bulging, active leaks — are stop-work signals, not logging items.