Offshore boarding valve is used for isolating the offshore facility such as production platforms, compression platforms, FPSOs, etc. from riser. It is also called boarding shut-down valve, riser isolation valve, or riser emergency shutdown valve.
At topside these valves should be located as low down the riser as practicable, so as to minimize the likelihood of damage below the boarding valves causing release of pipeline/riser inventories.
Flanges on the pipeline side of the riser boarding valves should not be used unless subsea isolation valve is installed and the shut in volume is sufficiently small. There shall not be instrument connections on the pipeline side of the riser boarding valve.
Riser boarding valves shall be located such that exposure to accidental loads is minimized. Riser boarding valves should be located in open naturally ventilated area and such that liquid accumulation below the valve is not possible. Offshore boarding valves shall be certified in accordance with recognized standard regarding fire resistance, and shall preferably have metal-to-metal seats.