Transport of backloaded contaminated bulk liquids, is currently performed according to local state rules. For this, there are now two entries in the revised IBC code. These are entered as Offshore contaminated bulk liquid P (o) and Offshore contaminated bulk liquid S (o), respectively. Both entries are IMO Ship Type 2 products and falling outside of the scope of A.673. In a trepartite agreement initiated by Norway, there is a 3rd entry for ”offshore contaminated bulk liquids Treated” that has been processed to remove or prevent the breakout of H2S. The hazards relating to carrying contaminated bulk liquids from rigs to shore have had special attention as reports of hydrogen sulphide (H2S) emissions on deck and inside cargo rails have been of great concern.

- Offshore contaminated bulk liquid type P (no danger of H2S formation in the liquid) (Continued open ventilation)
- Offshore contaminated bulk liquid type S (Controlled ventilation 0.6 bar)
- Offshore contaminated bulk liquid “treated” (backload that has been treated with scavenger/biocide to control formation of H2S) (Controlled ventilation) (tripartite agreement Norwegian Maritime Authority)

With reference to “treated” - Offshore contaminated bulk liquids, Ventiq has designed an overfill protection system to ensure free ventilation and to prevent overpressurization of tanks carrying treated backloads.
The valve system ensures a ready to action configuration, without the use of manual procedures. When pumping liquid mud from the rig to the receiving tank on board an OSV, there is a real danger of bulk liquids rising from the tank and entering the ventilation line.