German KNF pump KNF model KNF price

KNF pumps operate by using impeller rotation to induce centrifugal motion in water. Before starting the pump, the pump casing and suction pipe must be filled with water. Then, start the motor to drive the pump shaft, causing the impeller and water to rotate at high speed. The water undergoes centrifugal motion, is thrown toward the outer edge of the impeller, and flows into the discharge pipe of the water pump through the flow channel of the volute casing.

KNF pump structural composition

The basic structure of a centrifugal pump consists of six parts: the impeller, pump body, pump shaft, bearings, sealing ring, and packing gland. 1) The impeller is the core component of the centrifugal pump; it has high rotational speed and high output power. The blades on the impeller play a major role, and the impeller must undergo a static balance test before assembly. The inner and outer surfaces of the impeller are required to be smooth to reduce friction losses from water flow. 2) The pump body, also known as the pump casing, is the main body of the water pump. It provides support and fixation and connects to the bracket where the bearings are installed. 3) The function of the pump shaft is to connect to the motor via a coupling and transmit the motor's torque to the impeller, making it the primary component for transmitting mechanical energy. 4) Sliding bearings use transparent oil as a lubricant, filled to the oil level line. Too much oil will seep out along the pump shaft, while too little will cause the bearing to overheat and burn out, leading to accidents! During water pump operation, the maximum bearing temperature is 85 degrees, and normal operation is around 60 degrees. 5) The sealing ring is also known as the leakage reduction ring. 6) The packing gland mainly consists of packing, a water seal ring, a packing sleeve, a packing gland cover, and a water seal pipe. The main function of the packing gland is to seal the gap between the pump casing and the pump shaft, preventing water inside the pump from leaking out and preventing outside air from entering the pump. This maintains the vacuum inside the water pump! When heat is generated by friction between the pump shaft and the packing, the water seal pipe directs water to the water seal ring to cool the packing, ensuring normal pump operation. Therefore, inspection of the packing gland requires special attention during routine inspections of the water pump. The packing should be replaced after approximately 600 hours of operation.

KNF pump maintenance

Centrifugal pump shutdowns are primarily caused by mechanical seal failure. Failure mostly manifests as leakage, with the following causes: 1) Leakage at the sealing faces of the stationary and rotating rings, mainly due to: end face flatness and roughness not meeting requirements, or surface scratches; particulate matter between the end faces, preventing uniform operation; improper installation or incorrect method. 2) Leakage of the compensation ring seal, mainly due to: deformation of the gland cover, uneven preload; incorrect installation; seal ring quality not meeting standards; incorrect seal ring selection. Actual usage indicates that the most common site of seal element failure is the end faces of the rotating and stationary rings. Cracking of the end faces of the rotating and stationary rings in centrifugal pump mechanical seals is a common failure phenomenon, with the main causes being: 3) Excessive gap at the sealing face during installation, preventing the flushing fluid from removing heat generated by the friction pair in time; flushing fluid leaks through the sealing face gap, causing overheating and damage to the end faces. 4) Vaporization and expansion of the liquid medium cause the two end faces to separate due to vaporization expansion forces. When the two sealing faces are forced into contact, the lubricating film is destroyed, causing overheating of the end face surface. 5) Poor lubricity of the liquid medium, combined with excessive operating pressure, causes asynchronous tracking rotation of the two sealing faces. For example, a high-speed pump has a rotational speed of 20445r/min, a sealing face center diameter of 7cm, and after operation, its linear velocity reaches as high as 75 m/s. If one sealing face lags and cannot track the rotation, instantaneous high temperature causes damage to the sealing face. 6) Blockage of the seal flushing fluid orifice plate or filter screen causes insufficient water flow, leading to mechanical seal failure.

KNF pump industry applications

Centrifugal pumps feature a compact structure, wide flow and head ranges, suitability for mildly corrosive liquids, multiple control options, uniform flow, stable operation, and low vibration. They do not require special vibration-damping foundations. Advantages include low costs for equipment installation, maintenance, and repair. They are widely used in industries such as electric power, metallurgy, coal, and building materials for transporting slurries containing solid particles. Examples include hydraulic ash removal in thermal power plants, ore slurry transport in metallurgical beneficiation plants, and coal slurry and heavy medium transport in coal washing plants. When a centrifugal pump operates, the pump must be placed on land, the suction pipe placed in water, and the pump must be primed before starting. Due to structural limitations, submersible centrifugal pumps and slurry pumps require the motor to be positioned above the water surface while the pump is submerged. Therefore, they must be fixed; otherwise, if the motor falls into the water, it will be scrapped. Furthermore, since the long shaft length is generally fixed, pump installation and use are more troublesome, and application scenarios are subject to many restrictions.

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