COOLING DOWN OF LOW TEMPERATURE LIQUID TRANSPORT PIPE

PURPOSE:To prevent a piping from being damaged due to bowing phenomenon in which the piping is distorted like a bow and to shorten cooling time by controlling the temperature of refrigerant supplied based on the temperature of the upper part of the piping and at the same time controlling the flow rate of the refrigerant supplied based on the temperature of the lower part of the piping. CONSTITUTION:When a refrigerant taken out of a liquefied gas tank 2 is introduced to a low temperature transfer piping 1 to perform cooling down, temperatures T1-Tn at points in the upper part of the piping are measured, a suitable refrigerant temperature is calculated with a temperature controller TC from the measurements, a mixture ratio is determined to give the calculated refrigerant temperature, and a valve 5 is operated. On the other hand, changes in the temperature t at a point in the lower part on the piping is observed to obtain a suitable flow rate by means of a flow rate controller FC and to control a valve 6. Thus the refrigerant is supplied at a suitable flow rate to the piping 1.