【Q&A Question 083】2016.07.12

The basic structure of a centrifugal pump consists of six parts, namely: the impeller, the pump casing, the pump shaft, the bearings, the sealing ring, and the stuffing box.

Motor, coupling, bearing housing, volute, impeller

Impeller, pump shaft, coupling, pump casing, shaft seal device, bearings, oil scrapper ring, axial force balancing device.

The basic structure of a centrifugal pump consists of six parts, namely: the impeller, the pump casing, the pump shaft, the bearings, the sealing ring, and the stuffing box.

It should include a volute-shaped pump casing, pump shaft, impeller, suction pipe, discharge pipe, foot valve, control valves, filling funnel, and pump base.

It mainly includes a volute-shaped pump casing, pump shaft, impeller, suction pipe, discharge pipe, foot valve, control valves, filling funnel, and pump base.

Impeller, balancing device, sealing device, pump body, drive mechanism

Bearings, impellers, pump casings, mechanical seals, packing seals, couplings,

Impeller, volute, elbow, diffuser chamber

The basic structure of a centrifugal pump consists of six parts, namely: the impeller, the pump casing, the pump shaft, the bearings, the sealing ring, and the stuffing box. 1. The impeller is the core component of a centrifugal pump; it features high rotational speed and high output power. The blades on the impeller play a key role, and the impeller must undergo a static balance test before being assembled. The inner and outer surfaces of the impeller must be smooth to reduce frictional losses in the water flow. 2. The pump body, also known as the pump casing, is the main component of a water pump. It serves a supporting and fixing function, and is connected to the bracket that holds the bearing. 3. The function of the pump shaft is to connect to the motor via a coupling, thereby transmitting the torque of the motor to the impeller; it is therefore the main component for transferring mechanical energy. 4. Bearings are components that are fitted over the pump shaft to support it; there are two types: rolling bearings and sliding bearings. Rolling bearings use butter as a lubricant, and the amount of lubricant applied should be appropriate – generally 2/3 to 3/4 of the bearing’s volume. Too much lubricant will cause heating, while too little will result in noise as well as heating! Sliding bearing centrifugal pumps use transparent oil as a lubricant, which is filled to the oil level mark. Too much oil seeps along the pump shaft and leaks away, while too little oil causes the bearings to overheat and get damaged, leading to accidents! During the operation of the water pump, the temperature of the bearings reaches up to 85 degrees; under normal conditions it is around 60 degrees. If this temperature rises, it is necessary to identify the cause (such as the presence of impurities, whether the oil has turned black, or if water has entered the system) and take prompt action! 5. The sealing ring is also known as a leak-reduction ring. An excessive gap between the impeller inlet and the pump casing allows water from the high-pressure area inside the pump to flow through this gap to the low-pressure area, which affects the pump’s flow rate and reduces its efficiency! Too small a clearance can cause friction between the impeller and the pump casing, leading to wear. To increase backflow resistance, reduce internal leakage, and extend the service life of the impeller and pump casing, a sealing ring is installed at the junction between the inner edge of the pump casing and the outer periphery of the impeller; it is advisable to maintain the sealing gap between 0.25 and 1.10 mm. 6. The stuffing box is mainly composed of packing, a water seal ring, a packing cylinder, a packing gland, and a water seal tube. The main function of the stuffing box is to seal the gap between the pump casing and the pump shaft, preventing the water inside the pump from leaking out and stopping outside air from entering the pump. Maintain a vacuum inside the water pump at all times! When heat is generated by the friction between the pump shaft and the packing, a water seal is used to channel water into the seal ring in order to cool the packing! Maintain the normal operation of the water pump. Therefore, special attention must be paid to the inspection of the stuffing box during the routine inspections of the water pump’s operation! The packing needs to be replaced after about 600 hours of operation.