扩口管路密封失效引起的平管嘴大径外圈锈蚀故障分析

Corrosion Analysis of Large Diameter Outer Ring of Flat Nozzle Caused by Sealing Failure of Flared Pipe Connector

针对某氧气浓缩器进气口扩口管路连接处平管嘴的锈蚀故障,采用宏观、微观分析手段,结合EDS能谱分析确定了平管嘴已发生深入金属基体的锈蚀,且锈蚀产物主要为Fe_(2)O_(3)。通过逻辑推导分析腐蚀介质的可能来源,通过有限元建模,分析实际装配中最常见的带偏角装配工况下扩口管密封面上的Mises应力和CPRESS接触压力分布,得出平管嘴锈蚀故障的原因为:因该处管路连接需周期性反复拆装,拆装操作容易出现不同轴偏角装配情况,造成导管扩口内锥面接触不均匀和异常变形,从而破坏了密封面完整性,使导管内部与平管嘴/外套螺母间的间隙之间形成连通通道,冷凝湿气或腐蚀介质可通过这些通道逐渐泄漏并聚集到间隙处,最终导致缝隙腐蚀发生。

Aimed at the corrosion failure of the flat nozzle at the connection of the inlet expansion pipe of an oxygen concentrator,by using macroscopic and microscopic methods and combining with EDS analyses,it was determined that the corrosion penetrated into the metal matrix of flat nozzle and the rust product was mainly Fe_(2)O_(3).The possible sources of corrosive medium were analyzed by logical derivation.Through finite element modeling,the Mises stress and CPRESS contact pressure distribution on the sealing surface of flared tube under the most common assembly condition with deflection angle in actual assembly were analyzed.It is concluded that the cause of corrosion failure of flat nozzle is that because the expansion pipe connection needs periodic and repeated disassembly,the assembly of different shaft deflection angles is easy to occur in the disassembly operation,resulting in uneven contact and abnormal deformation of the inner surface of the tube flare,which destroys the integrity of the sealing surface and forms a communication channel between the tube inside and the sleeve nut/flat nozzle gap.Condensed moisture or corrosive medium can gradually leak through these channels and accumulate at the gap,resulting in crevice corrosion.