●Close-Interval Potential Survey
PL-06″ SGPC–TIPU · 10,933 readings at 1.5 m · NACE SP0207
Length surveyed
16.4 km
100% of the section
Below criterion
4.0 km
24% of the section
Minimum instant-OFF
−698 mV
at KP 12.400
Readings taken
10,933
1.5 m nominal spacingPotential profile — ON and instant-OFF
KP 10.0–14.0 below criterionThe gap between the two traces is the IR drop. A survey recording only ON potential would show this section as protected — which is exactly the error close-interval surveying exists to catch.
Survey record
| Structure | PL-06″ SGPC–TIPU |
| Section | KP 0.000 – 16.400 |
| Survey dates | 11–12 March 2026 |
| Crew | A. Sattar + 2 |
| Reading interval | 1.5 m (nominal 5 ft) |
| Readings taken | 10,933 |
| Interruption | 4 s ON / 1 s OFF, GPS-synchronised |
| Interrupted units | TR-01, TR-04 |
| Reference cell | Cu/CuSO₄, calibrated 09 Mar (±5 mV) |
| Procedure | NACE SP0207 |
| Criterion | −850 mV instant-OFF, AMPP SP0169 |
●Section Analysis
continuous lengths assessed against −850 mV instant-OFF| Chainage | Length | Min instant-OFF | Mean | State | Probable cause |
|---|---|---|---|---|---|
| KP 0.000 – 4.000 | 4.000 km | -1002 mV | -1042 mV | Protected | — |
| KP 4.000 – 8.000 | 4.000 km | -948 mV | -968 mV | Protected | — |
| KP 8.000 – 10.000 | 2.000 km | -880 mV | -894 mV | Protected | Approaching criterion |
| KP 10.000 – 14.000 | 4.000 km | -698 mV | -782 mV | Unprotected | Coating holiday DC-2201 at KP 12.400 |
| KP 14.000 – 16.400 | 2.400 km | -968 mV | -988 mV | Protected | — |
●Reading Log — KP 11.800 to 13.000
the close-interval detail through the defect| Chainage | ON (mV) | Instant-OFF (mV) | IR drop (mV) | Criterion |
|---|---|---|---|---|
| KP 11.800 | -1108 | -906 | 202 | Pass |
| KP 12.000 | -1074 | -868 | 206 | Pass |
| KP 12.100 | -1021 | -822 | 199 | Fail |
| KP 12.200 | -962 | -768 | 194 | Fail |
| KP 12.300 | -905 | -724 | 181 | Fail |
| KP 12.400 | -872 | -698 | 174 | Fail |
| KP 12.500 | -898 | -715 | 183 | Fail |
| KP 12.600 | -944 | -759 | 185 | Fail |
| KP 12.700 | -991 | -806 | 185 | Fail |
| KP 12.800 | -1036 | -851 | 185 | Marginal |
| KP 12.900 | -1078 | -889 | 189 | Pass |
| KP 13.000 | -1112 | -921 | 191 | Pass |
Extract of 12 readings from 10,933. The instant-OFF minimum sits directly over the DCVG indication at KP 12.400 (34% IR) — the two surveys locate the same defect independently, which is the corroboration ECDA requires under NACE SP0502.