Importance

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Abstract

The invention provides a self-priming centrifugal pump capable of sucking up and pumping a highly viscous liquid containing muddy substances including a large amount of bubbles, and solid foreign matters, of preventing the flow of the liquid from the side of a main pump unit into a vacuum device and from the vacuum device into the main pump unit at all stages of operation including starting, operating and stopping stages and of perfectly automatic operation, and very economical in costs of equipment and maintenance. The self-priming centrifugal pump has a main pump unit for pumping a liquid, an auxiliary pump unit for centrifugal gas-liquid separation, and an exhaust vacuum device. A region in the vicinity of a central part of an impeller included in the main pump unit is connected via a passage having a small passage area as compared with the discharge ability of the auxiliary pump unit to the suction opening of the auxiliary pump unit, the discharge opening of the auxiliary pump unit is connected to the suction opening of the main pump unit by a return passage, and a region in the vicinity of a central part of the impeller of the auxiliary pump unit is connected via an exhaust passage to the vacuum device. The exhaust passage includes in series therein a slow-acting valve which opens with a delay after the connection of a prime mover for driving the self-priming centrifugal pump to a power source, and a quick-acting valve which closes immediately after the disconnection of the prime mover from the power source.

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First Claim