PRESSURE CONTROL METHOD AND APPARATUS FOR KEEPING COOL LAYER OF LOW-TEMPERATURE TANK

摘要

PURPOSE:To control the pressure of a keeping cool layer interposed between an inside tank and an outside tank within the set range by heat exchange between gas in the keeping cool layer and the outside air or a low-temperature liquid in the inside tank. CONSTITUTION:When a pressure detector 14 detects that the pressure in a keeping cool layer 4 rises above a set range, a control valve 12 and an electromagnetic valve 10 are opened in response to a command of a controller 15. Therefore, high-pressure keeping cool gas is once expanded in an expansion tank 5 exposed to the air to be conducted into an inside tank 2 through a pipe 8, and then cooled at a heat exchange portion 7 to be returned to the keeping cool layer 4. When the pressure detector 14 detects that the pressure in the keeping cool layer 4 falls below the set range, the control valve 12 and an electromagnetic valve 9 are opened so that high-pressure keeping cool gas is expanded in the expansion tank 5 to be returned to the keeping cool layer 4.