Double-Suction Pump Efficiency Analysis

Reasons for the Decrease in Double-Suction Pump Efficiency:
1. Due to the scouring of water, the inner walls of the pump flow passages and the surfaces of the impellers become rough and uneven, increasing the friction coefficient of the flow passages. Combined with the high flow velocity inside the pump, this leads to increased head loss and reduced hydraulic efficiency.

2. The addition of chemicals before the pump or water quality issues can cause severe scaling or corrosion inside the pump casing. Severe scaling can increase the casing wall thickness by about 2 mm, and scale nodules on the pump's inner walls reduce the pump volume, decrease the pumping capacity, roughen the flow passages, and increase head loss. Both volumetric efficiency and hydraulic efficiency are reduced.

3. Foundry defects, cavitation, abrasion, corrosion, and chemical erosion caused by the pump manufacturing process can create cavities or cracks inside the pump flow passages, which generate vortices during water flow, causing energy loss. Hydraulic efficiency decreases.

4. Cavitation on the impeller surface. Negative pressure occurs on the suction side of the blade during operation. When the pressure Pk < Pva, cavitation and surface pitting occur on the impeller. Electrochemical corrosion then causes pump impeller cavitation.

5. Volumetric and mechanical losses. Prolonged use of the pump leads to mechanical wear, resulting in leakage and increased resistance, which reduces volumetric efficiency and mechanical efficiency. The above reasons cause the pump's performance to decline. Operating efficiency decreases by 2–5%, and in severe cases, pump efficiency can drop by more than 10%.