某电厂锅炉屏式再热器夹持管爆管原因分析

CAUSE ANALYSIS OF CONTINUOUS TUBE BURST ON HOLDING PIPES OF THE SCREEN-TYPE REHEATER FOR BOILER NO1 IN ONE POWER PLANT

对某电厂发电机组锅炉屏式再热器(屏再)夹持管连续多次爆管原因进行了分析,认为在焊接过程中未能严格执行焊接工艺要求,致使焊接接头的热影响区产生晶粒粗大和黑色网状晶界的不良组织,并且焊后热处理不当使熔合线产生了沿晶裂纹,这些裂纹在机组运行过程中逐渐扩展造成管子沿焊缝熔合线开裂。对此,建议加强设备监造,对重要的承压部件进行无损探伤抽检和理化性能试验。

The causes leading to continuous and frequent tube bursts on holding pipes of screen-typ reheater for boiler no1 in one power plant have been analysed,it is believed that the requirements of welding process hadn＇t strictly implemented during the course of welding,resulting in bad structure of coase-grained and black-reticulated grain boundaries appeared in the heat affecting areas of welded joints.Owing to unsuitable heat treatment after welding,the along-crystalline cracks are occurred on fusion lines,these cracks expand in operation,resulting in rupture along fusion line of the welding joints on pipes.It is recommented to further strengthen the supervision in manufacturing the equipments,and to carry out non-destructive inspection and physico-chemical test for the important pressurized parts.