浮顶储罐二次密封油气空间放电分析

Analysis on Second Sealing Oil and Gas Space Discharge in Floating Roof Tank

为避免浮顶储罐在遭受雷击时由于导电片设施在二次密封油气空间中放电引起密封圈火灾,在实验室建立了2 m直径油罐模型,开展导电片火花放电起始电流试验、导电片与罐壁形成空气间隙击穿放电初始电压试验,系统研究导电片在二次密封油气空间中的放电危险性。试验结果表明：导电片靠自身弹性与罐壁贴合时,雷电流大约在400 A时导电片开始产生点燃性火花放电;如导电片与罐壁贴合不良形成空气间隙,雷击情况下雷电流泄放瞬时浮顶与罐壁之间的电位差足以使一定大小的间隙击穿放电,当间隙大小为20~30 mm时,放电电压为26~40 kV。因此,储罐在遭受雷击时,导电片火花放电现象不可避免。结合储罐的实际运行情况,提出取消二次密封导电片、液下刮蜡器与浮顶进行可靠电气连接的改进措施,避免导电片在二次密封油气空间中放电发生,大大降低浮顶储罐雷击火灾事故。

In order to avoid floating roof tank sealing ring fire caused by shunts discharge in the second sealing oil and gas space due to lightning,this paper established a 2 m diameter tank model and carried out a shunts spark discharge experiment and an air gap breakdown discharge experiment,so as to systematically research shunts discharge risk in the second sealing oil and gas space.Experimental results show that Shunts attached to the shell by its own flexibility can generate sparks when the lighting current flow reaches a peak of about 400 Amperes;If there are gaps between shunts and the shell during lightning high voltage stock,potential difference between the roof and shell may break down the gaps and cause sparks,when the gap between 20-30 mm,discharging voltage is about 26-40 kV.Therefore,shunts spark discharge is inevitable as tank suffering from lightning.Finally,combined with the actual operation of the storage tanks,improvement measures were put forward,such as canceling shunts on the second seal and submerged paraffin scraper device reliable electrical connection with floating roof and avoiding shunts discharge in the second sealing oil and gas space,so as to greatly reduce floating roof tank lightning fire accident.