To prevent the damage of a bearing part by pouring a spring from a bearing circulation line to a non-seal type pump before the start of the non- seal type pump having a bearing circulation line and also draining from the bottom of the casing of the non-seal type pump and stopping/starting the supply and discharge of a spring after cleaning.

Dust and rust are gathered in a casing 1, during the stop and standby of pump. Therefore, at the start time of the pump, valves 11, 16 are opened prior to the start and the spring is supplied from a spring line 10 to a bearing circulation line 8 and poured in a circulation direction. In other words, the spring is drained from a blow line 15 via the bearings 6a, 6b in the casting 1 and an impeller 4 in order. Thereby, the dust and rust in the casing 1 poured out and its inside is cleaned. Next, after opening a check valve with a valve opening function 17 and cleaning a suction line side, the valves 11, 16 are closed and the pump is started. Such operation after cleaning the inside of the casing 1 and suction line side prevents the damage of the bearings 6a, 6b effectively.