See HARBOUR for max. size specifications.
There are no official size restrictions at Rio Grande. Biggest vessels able to operate loading grains are Capesize (as noted in Harbour Facilities) and biggest vessels that have operated in bulk discharge of fertilisers have been of about 80.000 DWT/260 mts LOA, same apply for tankers operating at Petropier.
The maximum dimensions mentioned do not necessarily apply to all berths, quays or areas within the port.