The importation of non-polutional natural gas shall be predestinated with a very rapid increase in its demand especially in U.S.A. (also in Japan and Europe), in co-operation with the established developements of transporting Liquefied gases in oceangoing tankers, although the overall investments of such projects as for gas source, LNG carrier and storage, comes to huge amount involving difficulties to be solvable. There have been under consideration to make further building for such typical four systems in LNG carries as “self-supporting prismatic tank”, “self-supporting spherical tank”, “membrane tank” and “semi-membrane tank”. Three dimensional stress analysis by finite element method have been established and available to tank design, although several discussions being done to make identify the view of dynamical design loads and concerned allowable stress in connection with Regulatory Bodies. And also several experimental researches through the fabrication of model tank are still proceeding in shipbuilding yard to obtain the conclusion of tank material to be selected incorporating together with fabricating methods, from which actual working procedure shall be established. With regard to insulation and piping system, several experimental researches are also proceeding to obtain developed insulation material and to have their fabrication methods established to meet cryogenic use. This paper explains the overall on cryogenic techniques on ships carrying LNG close to atmospheric pressure, in such several items as for containing systems, tank, insulation, piping and instrumentation.
Matsushita radio carbon resistors (grade ERC-18GK nominal resistance 100Ω and wattage 1/8) are found to have useful characteristics for the thermometer in a temperature range between 0.4K and 4.2K. Their characteristics are reproducible to within 1.5% in average after thermal cycling between room temperature and 1K. Temperatures calculated by the formula T=(AlogR+B/logR+C)-1 are within 0.01K from that of measured temperatures in the region 0.4K-4.2K. The sensitivity is about 300Ω/deg. at 0.4K.
Instability problem of V3Ga tape is studied for the case where a magnetic field is applied perpendicularly to the broad face of the tape which has a transport current. Stability of the tape against a flux jump is first analyzed, and the transiently stabilized maximum current is formulated. Experimental investigation is done by a method where a small coil made from V3Ga tape is located in another superconducting solenoid so that their central axes cross at right angle. Various coils which differ in cooling conditions, thickness of stabilizing copper, and width of the tape are tested in a preset current-increasing field. For a preset current which is smaller than a threshold value, coils do not go normal even if large flux jumps are observed. But for a current above the threshold value a first flux jump makes the coil normal. The threshold current depends on the tape width, cooling conditions, and the thickness of the stabilizing copper. It is found that the threshold current is very close to the quenching current of a larger V3Ga tape coil.