Scope of this guide
Management version: this defect as cost and risk — the metrics, audit points and claim defence.
Series: finishing.com recurring questions answered with platingclub line practice. Parameters are industry-standard starting ranges — confirm against your supplier TDS.
Triage: symptom → confirm → first move
| Symptom | Likely root | Confirm by | First move |
|---|---|---|---|
| Rough, gritty deposits | Bag burst: sludge bleeding | Bag inspection under load | Replace bag, polish filter |
| Anode current falls | Bags clogged / anodes passivated | Voltage vs amps trend | Clean or re-bag anodes |
| Nickel content drifts down | Anodes not dissolving | Daily metal titration | Check bag choke and anode area |
| Particles despite filter | Sludge already in bath | Filter ΔP + housing check | Full filter service; settle, syphon |
| Recurring after refill | Bad bag media or wrong size | Bag spec audit | Standardize bag spec per tank |
Cost, metrics and defence
| Cost line | Driver | Metric | Lever |
|---|---|---|---|
| Scrap events | Sludge rain on racks | Bag failures per year | Dated replacement ledger |
| Filter spend | Bags failing into filters | ΔP trend per tank | Inspect before filters load up |
| Downtime | Emergency re-bagging | Planned vs emergency share | Schedule by tank, not by crisis |
| Metal drift | Passivated anodes | Daily titration variance | Anode area + bag choke checks |
Engineer notes
- One variable per corrective action; verify with the confirm-by column.
- Records beat memory: log every trial on the tank card.
- Two failed actions in a row is a senior call — escalate with your log.
Safety: anode work means live bus bars and hot, chemical-soaked bags. Lock-out before touching baskets, drain and rinse bags outside the tank, gloves and shield throughout.
FAQ
Bags are cheap — why track them?
Because their failure mode is scrap events, not the bag price; ledger cost is trivial vs one sludge incident.
Which KPI predicts bag failure?
Tank age since last bag change plus ΔP trend; replace on the curve.
Who owns the weekly inspection?
Equipment tech with the walk card; audits check the card and the bags' dates.