The handling liquid for tankers varies widely from low viscosity to high viscosity liquid. Recently, even VLCC starts handling high viscosity liquid. Since the heating device is not equipped to the cargo tank of VLCC, it is quite important to examine whether it is possible to discharge at the unloading port even though the viscosity at loading port was not high by heating. And cargo oil pump and ballast pump require a lot of valve manipulation during unloading and de-ballasting and there is a case of water hammer due to wrong manipulation and pump becomes inoperative. As a recent trend, it is occurring on ballast pump. There is a case of abnormal temperature rise of pump bearing occurs depending on the unloading condition. This is introducing cautions for these matters.