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瓷制切口由于湿气进入, 继而反复冻融的一个失败故障例子
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瓷制切口由于湿气进入, 继而反复冻融的一个失败故障例子

May 9, 2015 • Photo of the week

照片显示的是什么? 这是一个陶瓷切口的故障实例,由于湿气进入随后反复冻融。 在哪里拍照的? 这个缺口是从网络中撤下的位于加拿大西部电力企业的实例。 有什么意义? 此类型的问题进行调查后发现大约安装在该电力公司的配电网络的有32700个切口,自2004年以来共有132类似的案件,占0.4%的累计故障率。这个比率对制造失败切口的日期的相关性表明,在受影响的单元的相对寿命没有显著冲击破坏的发生率。这已经比服务场所几年的较老的缺口的速度更快。得出的结论是,故障是由于本地服务条件老化过程中的生产的不良设计和质量控制问题。例如,如果粘结到切口壳体的金属管件进入通过不良制造与烤瓷直接接触,将发生一个固有缺陷。当切口暴露于高温时,金属膨胀可以破解陶瓷。故障的第二原因是更常见的方式涉及到用来防止湿气进入单元的涂料或环氧密封剂。如果此处的密封剂老化,就会发生湿气进入。然后随后的冻融循环会导致裂纹和最终失败。失败的另一个原因是由于处理不当或安装造成,导致芯片或发生在陶瓷的应力造成损伤。 An example of failure of a porcelain-housed cutout due to moisture ingress followed by repeated freeze-thaw cycles

What does the photo show?

This is an example of failure of a porcelain-housed cutout due to moisture ingress followed by repeated freeze-thaw cycles.

Where was the photo taken?

This cutout was removed from the overhead network at a power utility located in western Canada.

Why is it interesting?

An investigation conducted into this type of problem revealed that of circa 32,700 cutouts installed on the distribution network at this power utility, there were 132 similar cases since 2004, representing a cumulative failure rate of 0.4%. Correlation of this rate against date of manufacture of the failed cutouts showed that the relative age of the affected units did not significantly impact incidence of failure. Units that had been in service only a few years were failing at about the same rate as much older cutouts. The conclusion was that failures were as much related to poor design and quality control problems during manufacture as to ageing under local service conditions. For example, if the metallic fittings cemented into the cutout housing come into direct contact with the porcelain through improper manufacturing, an inherent weakness is created. When the cutout is exposed to high temperature, the metal expands and can crack the porcelain. A second and more common mode of failure involves the paint or epoxy sealant used to prevent moisture from entering the unit. If this sealant deteriorates, there can be moisture ingress. Subsequent freeze-thaw cycles will then lead to cracks and eventual failure. A further cause of failures is damage occurring due to improper handling or installation, causing chips or creating stresses in the porcelain body.
Porcelain cutouts in the Okanagan have experienced cracking due to cycles of moisture penetration combined with cold temperatures. failure 瓷制切口由于湿气进入, 继而反复冻融的一个失败故障例子 pic15

Porcelain cutouts in the Okanagan have experienced cracking due to cycles of moisture penetration combined with cold temperatures.

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