Basic Construction of Centrifugal Pumps
Basic Construction of Centrifugal Pumps
The basic construction of a centrifugal pump consists of six main parts: impeller, pump casing, pump shaft, bearing, sealing ring, and stuffing box.
Impeller:
Pump Casing (or Pump Body):
Pump Shaft:
Bearings:
Sealing Ring (or Wear Ring):
Stuffing Box:
• The impeller is the core component of a centrifugal pump. It operates at high speed and delivers significant output. The blades on the impeller play a crucial role. Before assembly, the impeller must pass a static balance test. The inner and outer surfaces of the impeller need to be smooth to minimize water friction loss.
• Also known as the pump shell, it serves as the main body of the pump, providing support and fixation. It is connected to the bracket that houses the bearings.
• The pump shaft connects to the motor via a coupling and transmits the motor's torque to the impeller. It is the primary component for transferring mechanical energy.
• Bearings are components that support the pump shaft, available in two types: rolling bearings and sliding bearings. Rolling bearings use grease as a lubricant, and the oil level should generally be between 2/3 to 3/4 full. Too much or too little can lead to overheating or noise. Sliding bearings use transparent oil as a lubricant, and the oil should be added up to the oil level line. Excessive oil can seep along the pump shaft and splash, while insufficient oil can cause the bearing to overheat and fail, leading to accidents. During operation, the temperature of the bearing should not exceed 85°C, typically operating around 60°C. If the temperature rises, it is necessary to investigate the cause (such as contamination, darkened oil, or water ingress) and address it promptly.
• Also referred to as a leakage reduction ring, the sealing ring is installed at the junction of the pump casing and the outer edge of the impeller. Its purpose is to increase the resistance to backflow and reduce internal leakage, thereby extending the life of the impeller and pump casing. The ideal gap between the sealing ring and the impeller should be maintained within 0.25 to 1.10 mm.
• The stuffing box primarily consists of packing material, water seal ring, stuffing box cylinder, packing gland, and water seal pipe. Its main function is to seal the gap between the pump casing and the pump shaft, preventing water inside the pump from leaking out and outside air from entering the pump. It maintains the vacuum inside the pump. When the pump shaft and packing material generate heat due to friction, water from the water seal pipe cools the packing material, ensuring the normal operation of the pump. During routine inspections of the pump, particular attention should be paid to the condition of the stuffing box. The packing material should be replaced after approximately 600 hours of operation.
