Pump Casing
Japanese

The pump casing consists of several stages of volutes and the pump casing of one unit construction. Since the volute chamber is of multiple type, the pressure applied to the periphery of impeller is distributed symmetrically to the shaft center. Accordingly, the radial thrust applied to the impeller is balanced at each stage and no shaft bending force is generated.
The volutes are set at the even number stages, arranged symmetrically in equal number in the pump casing.

Impeller and Inducer
Japanese

The impellers are of single suction type and are provided in the even number of stages in order to keep the axial thrust in balance, being arranged symmetrically in the equal number.
The inlet of the 1st stage impeller is provided with the inducer with the spiral blades in order to minimize NPSH of the pump.
The impellers are positioned at the shaft by means of the sleeves and two-piece ring keys. Accordingly, no such work is required at the reassembling time as the special dimension measurement, positioning adjustment, etc.

Balance Mechanism
Japanese

Hydraulic thrust of the impeller is completely balanced by the symmetrical arrangement of the impeller.
In case of low pressure pump, a balance sleeve is provided at the upper end of the shaft, and the upward thrust is generated by the intermediate stage pressure acting on the lower face, then the weight of the rotating element loaded to the lower ball bearing is alleviated.
In case of high pressure pump, auto balance mechanism is provided at the upper end of the shaft, so no axial thrust is acting to the ball bearing.

Bearing
Japanese

At the upper and lower parts of the motor shaft, one set each of the single row deep groove type ball bearing (63 model) is provided. The inner and outer rings and also the balls are made of stainless steel, while the cage is prepared with the teflon system resin. Between the stages of the pump, the submerged bearings are provided in order to support the impeller shaft, and the structure is so arranged to support the accidental radial thrust as well.

Cooling of Ball Bearing and Motor
Japanese

The ball bearing and motor are cooled off by a part of the liquefied gas (pumping liquid) which has the intermediate stage pressure of the pump.
The cooling liquid performs the lubrication and cooling for the lower ball bearing, motor and upper ball bearing, and then is discharged in the barrel.

Demagnetization of Ball Bearing
Japanese

A special consideration is paid to prevent the magnetization of the ball bearing, since the magnetized bearing attracts the iron powder in the liquid and the bearing is damaged.

Coil
Japanese

A special consideration is paid to the coil insulation in view of the fact that the coil is used in the cryogenic liquid. As the coil wire, the form wound coil is used and the mechanically and electrically rigid construction is formed with the special synthetic resin insulation materials.

Connecting Pipe and Junction Box
Japanese

The both ends of the connecting pipe are provided with the tightly sealed terminal header made of the electric insulation materials. Thus, the complete air-tightness is maintained so that the cryogenic temperature inside the motor frame may not be conducted to the junction box.
The junction box is of pressure resistant explosionproof structure (Exd) and is connected to the motor body with the connecting pipe.

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