Abstract
Regarding to the cryogenic spill protection insulation design for the structural steel, the major concerns from design aspect are defining 1) Phase of spilled cryogenic hydrocarbon on the steel structure (i.e. liquid fraction) which affect the thickness of cryogenic spill protection (CSP) insulation, and 2) Extent of brittle fracture hazard area due to cryogenic hydrocarbon spill. However, there is no standardized approach defining these two points yet. Currently, the phase of spilled cryogenic hydrocarbon is assumed as liquid phase in order to set insulation thickness conservatively, and the extent of brittle fracture hazard area is assumed differently project by project.
This paper proposes to the engineering approach to determine 1) Phase of spilled cryogenic hydrocarbon on the steel structure which affect the thickness of CSP insulation, and 2) Extent of brittle fracture hazard area due to cryogenic hydrocarbon spill. Based on the principle of heat transfer phenomena for liquid, wet spray, and dry jet exposure on the steel structure, it is assumed that the significant temperature drop will occur due to latent heat of vaporization. Thus, this paper focuses on the wet spray phase of the cryogenic hydrocarbon spill on the vertical steel column, where cryogenic liquid film can be developed, rather than the dry jet phase.
In order to determine the adequate phase of cryogenic hydrocarbon spill to determine the thickness of cryogenic spill protection insulation for wet spray exposure on the vertical steel structure, experimental test is conducted based on the several flow rate of cryogenic wet spray and the accumulation of cryogenic liquid. Test results are evaluated against heat transfer calculation results. As a conclusion, the liquid nitrogen accumulation test is proposed as reasonable and enough conservative phase to determine the thickness of CSP insulation for vertical steel structure against the wet spray exposure. In addition, the heat transfer analysis is conducted to identify critical condition for steel structure rapidly causing brittle fracture which is demonstrated as liquid ratio in spilled cryogenic hydrocarbon, and decide the criteria of the cryogenic wet condition on the steel structure. Based on the defined criteria of the cryogenic wet condition, the traveling distance of spilled cryogenic liquid is calculated. The calculation method is evaluated by the experimental test using liquid nitrogen and concluded as reasonable and enough conservative side to use the calculation method.
