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Evaporator Failure Caused by Corrosion and Flow

机译:腐蚀和流动引起的蒸发器故障

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This paper deals with three cases of boiler tube failure.1). Flow assisted chelant corrosion was concepted as reason for inadmissible thinning of economizer tubes. There were discontinuous orange peel and extremely thin layer of iron oxides on those scalloped waterside. Some pearlite grains with iron leached off were found in surface vicinity under oxides layer.2) Caustic gauging was recognized as damage mechanism of evaporator arch tube. The failure was localized in vicinity of protruding weld seam. It had character of ellipsoidal funnel with solid dense piece of iron and copper oxides inside and thin sodium contained deposit between the deposit and tube surface. The last was significantly etched under the deposit.3) Quasi corrosion cracking was real cause for bent tube rupture by an axial crack. Neither internal attack nor significant structure degradation was observed in crack vicinity. The crack sides were strongly oxided and ash constituents penetrated into the crack. Nothing like said was found in neighborhood, hence the fault tube was "pre-cracked" before its service beginning, for instance due to inefficient heat treatment after bending.
机译:本文涉及锅炉管故障的三种情况。 1)。流动辅助的螯合剂腐蚀被认为是导致省煤器管变薄的原因。在那些扇贝状的水边有不连续的橙皮和非常薄的氧化铁层。在氧化物层下面的表面附近发现了一些铁浸出的珠光体晶粒。 2)腐蚀仪被认为是蒸发器拱管的损坏机理。失效局限于突出的焊缝附近。它具有椭圆形漏斗的特征,内部有固态致密的铁和氧化铜片,并且在沉积物和管子表面之间含有稀薄的钠沉积物。最后一块明显蚀刻在沉积物下方。 3)准腐蚀裂纹是由轴向裂纹导致弯管破裂的真正原因。在裂纹附近既未观察到内部侵蚀也未观察到明显的结构退化。裂纹的侧面被强烈氧化,并且灰分成分渗透到裂纹中。在附近没有发现任何类似的东西,因此故障管在开始使用之前就被“预破裂”,例如,由于弯曲后热处理效率低下。

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