Fire Hazard Analysis And Fire Fighting System Research For A LNG Carrier

With the rapid growth of natural gas demand of our country, the frequency of liquefied natural gas (LNG) carrier which wanders around the domestic port increases greatly. The possibility of LNG spills which may cause fires or blasts increases with the increasing of LNG transportation quantity. The fire hazard caused by the spills of LNG carrier was analysed and the fire fighting system of LNG carrier was researched in this paper.Models for predicting the dynamics of spill from an orifice which is above the sea level or underwater within a LNG carrier have been established respectively based on the fluid mechanics principle, the correlations between the spillage, the release velocity, mass flow rate and the orifice position were proposed. Aiming at the case of the orifice above the sea level, the spill models obtained were analyzed and verified based on an analysis example, the result shows the spill duration with regard to the average spill rate is very close to the exact time. The fire and explosion hazard analysis while spilling has been completed, the pool fire radiation equation was obtained based on solid flame model, expressions of the flame surface emissivity, atmospheric transmittance and geometrical view factor between the radiation receiving object and the radiation emitting part of the fire were given. The models can provide valuable support for establishing the fire fighting scheme of LNG carrier and the fires hazard assessment.The fire fighting system scheme for a LNG carrier was carried out based on the domestic fire fighting design codes and the advanced fire fighting experience of overseas. In view of the special risk of the LNG carrier, the Fire and Gas System was chosen as the LNG spill detection and fire alarm system of LNG carrier; The fire fighting water system, water mist fire suppression system, high expansion foam extinguishing system, dry chemical powder system and fire extinguisher were chosen as the fire extinguishing system; according to the characteristic of LNG fire, an effective fire fighting step of LNG carrier and the fire fighting method to extinguish LNG fire were analyzed.The scheme design for LNG spill detection and fire alarm system was carried out based on the traditional fire alarm system, the match plan for selecting the fire and gas controller, addreaasble alarm system and the detection sensor on the spot. The research results of an oversea experiment which is to study the effectiveness of high expansion foam to suppress LNG pool fire was analyzed, the high expansion foam system for an LNG carrier was designed based on the analysis result obtained. The chemical dry powder fire extingsuishing system was designed; the combined application of high expansion foam and dry powder to suppress LNG pool fire was analyzed, which provide the reference for controlling and extinguishing the fire caused by LNG spill effectively.