Approach = sat. cond. temp − SW outlet. Flat and low = clean. A rise that sea-water temperature doesn't explain = fouling. Clean above 16 °C. R449A glide (~5 K) → differences under ~2.5 °C are noise.
HP (bar g) interpolated on the corrected Honeywell R449A table. Anchors 17.0→40.6 · 19.0→44.5 · 20.0→46.3 (45 °C ≈ 19 bar g). Zeotropic mean value, ±2.5 °C.
On a clean condenser the points sit in a flat low band whatever the sea-water temperature. Fouling shows as the band lifting for a given inlet temp. Green = after the 07 Jul clean, amber = before — if green sits at or below amber, fouling was removed and hasn't returned.
HP against sea-water inlet is a tight line when healthy. If it drifts upward over weeks at the same inlet temperature, that's fouling confirming itself independently of the approach calculation.