针对越南某电厂220 MW机组在启动调试阶段3号低压加热器疏水不畅的问题进行分析。在所采集实时运行数据的基础上，结合原设计参数及现场情况，通过对2、3号低压加热器疏水系统进行改造及对冷渣器冷却水量进行调整，消除了3号低压加热器疏水不畅问题。就冷渣器冷却水回水温度对3号低压加热器疏水的影响提出了解决办法。

This paper analyzed the reason of drain in block in No.3 low pressure (LP) heater in 220 MW units during the startup and debugging stage. Based on the real-time data, the original design parameters and the site situation, the drainage systems in No.2, No.3 LP heaters were modified, and the cooling water of slag cooler was adjusted, in order to solve the drain in block in No.3 LP heater. Finally, this paper suggested the solution for the influence of cooling waters backwater temperature in slag cooler on the No.3 LP heaters drain