Mactra, a new Shell VLCC, was tank cleaning off Africa
when an explosion occured in one of her cargo tanks.
This was a repeat of the Marpessa explosion two weeks earlier
except the ship did not sink.
It appears that this explosion was one tank further forward
than that of the Mactra.
This was one of the three big tank cleaning explosions in December 1969,
which led Shell to conclude that static electrictity created by
the tank cleaning jet of water was the probable source of ignition,
This in turn resulted in the requirement for inerting.
Howarth, A Century in Oil, p 295 has great picture of deck.
Damage extends from manifold back to pump room
in a sort of triangle with the base at the manifold
where it is at least the full width of the center tanks
narrowing at it moves aft.