Discharge ports have a minimum acceptable cargo temperature
Export of products, i.e. gas condensate, from ports exposed to low temperatures is increasing. For some ports, i.e. Vitino on the White Sea, the cargo is transported to the terminal by rail and stored in tanks exposed to the ambient air temperature.
Due to the transport and storage time it can be anticipated that the cargo will be close to the ambient air temperature. The terminal has no means for heating the cargo. When the cargo is delivered to the ship the terminal can inform the vessel of the cargo temperature, but it is the vessels responsibility to decide how to handle it, for example by low filling rates and/or use of ballast water to partially warm the cargo.
There can also be challenges at discharge ports. Based on information received from operators some discharge ports have a minimum acceptable cargo temperature. One operator indicated a minimum acceptable temperature for discharge of -4o C, but this will certainly vary from terminal to terminal. Another indicated that after a voyage from Vitino the cargo was still at a temperature of approximately -15o C upon arrival at Rotterdam and he was not allowed to discharge resulting in extended lay time.
DNV regularly receives requests for guidance/acceptance for loading product cargos at low temperatures for vessels not specifically designed for this. Temperatures as low as -20o C to -30o C have been requested. The material in some parts of the cargo tank boundaries is often grade A.
Grade A mild steel is not required to be charpy tested and its properties at low temperatures can not be guaranteed. This means that at these low temperatures there is a possibility that the steel is below the transition temperature and will be brittle with an increased risk of brittle fracture.
For more information, click here.
Source: DNV