A method and apparatus for ensuring against explosion of the
gaseous atmosphere of a
closed chamber, such as the QDCD room of an internal
turret of an offshore production and offloading
buoy wherein the
closed chamber has production risers and conduit connectors that represent a
potential source of
flammable gas. The method comprises mixing and diluting the oxidant content of the air by introducing within the
closed chamber a sufficient quantity of
inert gas to render the mixture of the air and any
flammable gas non-combustible regardless of the
flammable gas content of the mixture. The method includes removal of the non-combustible mixture of air and any flammable gas from the closed chamber by purging thereof to the natural
atmosphere, while introducing
inert gas, thereby leaving a substantially
inert atmosphere within the closed chamber. The
turret system provides for control of the
gaseous atmosphere within the closed chamber at all
modes of
turret operation, including the idle, on-line and ventilation
modes and also provides for
gas pressure control to accommodate normal operating conditions and conditions of gas leakage into the chamber.