In 1990, NHEF 33180 was converted to NPPF 33180 for Limestone traffic from Medway to Berrima Junction.
The conversion consisted of an additional reservoir tank on the underframe between the doors, additional pipework, additional air hoses, and air operated door rams fitted to all 3 doors.
At least 27 hoppers have been converted for Limestone Traffic.
These hoppers are still in use today.
On Track Models produces 2 packs of 4 models based on these wagons.