某300 MW机组循环水泵出力不足的诊断分析

某300 MW机组投产以来循环水流量不足，极大地影响了机组的经济性。通过试验诊断分析得到，循环水系统设计阻力小于实际值，导致按照设计阻力选型的循环水泵出力不足，使得循环水流量偏小，影响了机组运行的真空。根据循环水系统实际阻力特性，对循环水泵进行重新选型整体改造，取得了较好的效果，与改造前相比，供电煤耗降低1.174 ~1.200 g/（kW·h）。据此，提出了循环水泵在设计选型时的注意事项。

Diagnostic Analysis on Insufficient Output of Circulating Water Pumps for a 300-MW Unit

The circulating water flow is insufficient since the commissioning of a 300-MW generating unit, which greatly influences the economical efficiency of the unit. The testing analysis shows that the designed resistance of the circulating water system is less than the actual value, which leads to the insufficiently designed output of the circulating water pumps, so that the circulating water flow is too small to maintain the normal vacuum. According to the actual resistance characteristics of the circulating water system, new circulating water pumps are selected and substituted for the original ones, making the net coal consumption be reduced by 1.174~1.200 g/（kW·h）. The retrofit has achieved good effects. Therefore, some considerations in circulating water pump design and type selection are put forward.