主冷却剂泵石墨瓦磨损原因分析

Cause analysis of abrasion and cavitation corrosion on graphite pad

针对田湾核电机组主冷却剂泵(主泵)运行中出现的止推轴承石墨瓦块表面存在异常磨损的问题,根据水润滑轴承工作原理和磨损机理进行分析研究,发现磨损的主要原因是:1)主泵启、停过程摩擦副瓦块轴向载荷偏大;2)主泵内流体存在大量小气泡在高压作用下被压缩和凝结,使石墨瓦表面形成明显的空化腐蚀。因此,提出:1)长期投用电磁铁,可将主泵的轴向载荷由450kN降至约200kN(该方法正处于试验阶段);2)将主泵水箱封闭,采用盐水系统压力提高石墨瓦冷却回路静压力。该方案实施后主泵运行正常,未再发生因参数超标而导致的机组停机故障,有效解决了石墨瓦块表面磨损问题。

The abnormal abrasion of graphite pad surface on thrust bearing occurred during operation of the primary coolant pump（PCP）in Tianwan Nuclear Power Plant was analyzed,on the basis of the work principle and wear mechanism of the water lubrication bearing.It pointed out that the major reasons include：1）over large axial load of friction pairs during startup and shutdown of the PCP;2）obvious cavitation corrosion on the graphite pad surface,caused by agreat amount of bubbles being compressed and condensing at high pressures during fluid flowing in the PCP.Thus,several suggestions were put forward：1）using electromagnet for a long time to reduce the axial load of the PCP from 450 kN to about 200 kN,and this method is during the experimental stage;2）closing the PCP water tank and pressurizing the PCP water tank by saline system to improve the hydrostatic head of graphite pad cooling circuit.After the second method was adopted,the PCP ran normal and abnormal shutdown problems of the unit resulted by parameter over standard have never happened.