| 摘要 |
PROBLEM TO BE SOLVED: To provide a method of measuring an actual porosity of a second sealing barrier wall of a liquefied gas storing tank while a vessel is in operation without requiring a stop condition of the vessel in technical terms and also without exhausting liquefied gas out of the tank and introducing the ambient temperature. SOLUTION: According to this method of measuring the actual degree of porosity, the tank 20 includes two heat insulating layers installed on either side of the second sealing barrier wall 5. Inert gas exists in the insulating layers, where the pressure is controlled by valves 401, 402, 601, 602. The method comprises steps of: measuring and calculating the mean pressure P<SB>m</SB>and mean absolute temperature T<SB>m</SB>of the second insulating layer when the valves are closed and while the pressure in the free space of the first insulating layer 4 is kept at a value different byΔP from the value in the free space of the second insulating layer 6; and calculating the actual degree of porosity PO of the second sealing barrier wall using the formula PO=-(dP/dt)*(V/Pm)*((Pm*M)/(2*ΔP*R*Tm))<SP>1/2</SP>, where dP/dt is the change rate of the pressure P in the free space of the second insulating layer, V is the volume of the free space of the second insulating layer, M is the molecular mass of the inert gas, and R is the ideal gas constant. COPYRIGHT: (C)2008,JPO&INPIT
|
