German Kral pump Kral model Kral price

Kral pump is a type of pump that uses the rotation of helical blades to lift water axially in a spiral pattern. It consists of a shaft, helical blades, and a housing. During pumping, the pump is placed obliquely in the water so that the inclination angle of the pump's main shaft is less than that of the helical blades, with the lower end of the blades in contact with the water. When the prime mover drives the screw pump shaft to rotate via a variable speed device, water enters the blades, rises along the spiral flow channel, and exits. The structure is simple, easy to manufacture, offers high flow rate, low head loss, and high efficiency, and is easy to maintain. However, it has low head and low rotational speed, requiring a variable speed device. It is mostly used for irrigation, drainage, and lifting sewage, sludge, and other applications.

Kral pump working principle

The screw pump assembly includes the prime mover, the variable speed transmission device, and the screw pump, as shown in Figure 1. Specifically, it consists of helical blades 1, pump shaft 2, bearing housing 3, and housing 4. The screw pump is installed inclined between the upper and lower water pools, with the lower blades submerged below the water surface. When the pump shaft rotates, the helical blades push water from the pool into the blade slots. Under the action of the rotating helical blades, the water is lifted stage by stage along the spiral axis until it reaches the outlet of the screw pump. The screw pump only changes the potential energy of the fluid; unlike vane pumps, it does not convert mechanical energy into both potential and kinetic energy of the conveyed liquid.

Kral pump features

Compared with vane pumps, screw pumps have the following advantages: (1) Low rotational speed (generally 20r/min～90r/min), minimal mechanical wear, and no cavitation. (2) Wide flow channel, capable of conveying water containing solids. (3) The pump body structure is semi-open, allowing observation of internal operation. (4) The flow state on the suction side has little effect on hydraulic performance; there are no special requirements for the suction pool, foundation excavation depth is small, hydraulic construction is simple, and civil engineering costs are low. Disadvantages include: (1) Large size and large footprint. (2) Limited by machining conditions, the pump shaft cannot be too long, resulting in low head, generally not exceeding 10m. (3) The height variation between the suction water surface and the discharge water surface cannot be too large, otherwise it will affect work efficiency and increase energy consumption.

Kral pump troubleshooting

1) Severe vibration or noise from the pump body: Causes: Loose pump installation or excessive installation height; damaged motor ball bearings; bent pump main shaft or misalignment/non-parallelism with the motor main shaft. Solutions: Secure the pump or lower its installation height; replace motor ball bearings; straighten the bent pump shaft or adjust the relative position of the pump and motor. 2) Overheating of the drive shaft or motor bearings: Causes: Lack of lubricating oil or bearing failure. Solutions: Add lubricating oil or replace the bearings. 3) Pump fails to discharge water: Causes: Pump body and suction pipe not fully primed; dynamic water level below the pump filter pipe; cracked suction pipe, etc.

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