Abstract: Based on the fire dynamic simulator numerical method, the fire smoke spread law in deep water semi-submersible platform is studied. According to the most disadvantageous principles of fire scenario design, four fire cases are designed to investigate the fire smoke spread and distribution law of upward spreading ability along stairwell. And its influence on the distribution of extremum of temperature, visibility, CO volume fraction on the staircase of each deck are studied. The impact of height of fire deck on the distribution law of filling the deck within required time is analyzed. Its impact on the smoke spreading path is also analyzed.The results show that when the distance between the stairwell and the fire room decreases, the upward spreading ability of smoke along the stairwell will be strengthened. The maximum temperature, the shortest time of visibility reaching critical condition, the maximum CO volume fraction of decks above the fire deck are located in staircases with strong upward spreading ability of smoke. With the height of fire deck increasing, it would take shorter time for the smoke to fill the decks above the fire deck and longer time for that below the fire deck. The results can contribute to the design of fire protection and the evacuation path when the semi-submersible platform is on fire.

Key words: deep water semi-submersible platform (DWSSP); smoke spread law; distribution of extremum; height of fire deck