Abstract: The drainage of #7 and #8 low pressure heaters of a supercritical 600MW unit were impeded. The main causes were that the pressure difference in steam sides of #7 and #8 low pressure heaters was smaller, the level difference of drainage was larger and the resistance of drain pipe was larger. In the drainage reformation of a power corporation, the measures for reducing the system resistance, such as reducing the level difference of drainage, eliminating the drain valve, optimizing the pipe line allocation and so on, were adopted. After reformation and under the load greater than 300MW, the normal drainage of #7 and #8 low pressure heaters was realized.

Key words: low pressure heater, drain pipe, reformation of pipe line, argument of resistance, implement plan