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Ballast fouling level standard.
| Rank | Fouling Level | Fouling Index Sieving (%) | GPR Fouling Index | Maintenance Decision |
|---|---|---|---|---|
| 1 | Clean | <10 | <2.0 | No need for cleaning or renewal |
| 2 | Medium clean, | 10~20 | 2.0~3.5 | Keep focusing |
| 3 | Medium fouled, | 20~25 | 3.5~4.1 | On the plan list |
| 4 | Fouled | 25~30 | 4.2~4.8 | High level on the plan list |
| 5 | Highly fouled | ≥30 | ≥4.8 | Prior to others |
