＂Antique＂ manhole covers are still in use. Is there a ＂shelf life＂ for manhole covers？

　　"Antique" manhole cover citizen Cheng Renbin photo

　　Wuhan Evening News (Reporter Chen Qixiong) On the evening of September 9, when citizen Cheng Renbin passed in front of Yingfang North Community, No.399 Jianshe Avenue, Hankou, he saw two "antique" manhole covers on the sidewalk, one of which was made in 1974 and the other in 1986. He asked: What materials are these two lids made of? How long will they last?

　　Cheng Renbin, who lives in Hankou, is a curious person. In an interview with reporters, he said that the two manhole covers are close. One of the manhole covers is marked with the words "Dung Cover, Tunfang Company, 1974"; Another manhole cover is cast with the words "Wuhan Huangxiaohe Regulation Project Command System" and "1986".

　　Cheng Renbin said that he had never seen such an "antique-grade" manhole cover before. He wants to find out what materials these two manhole covers are made of. Are you in extended service? Why don’t the relevant departments replace them with new manhole covers?

　　Chen Zongfu, captain of the drainage team of Qiaokou District Water Affairs Bureau, told the reporter that the two manhole covers that Cheng Renbin saw were made of high-quality ductile iron, and one was made in 1974 and has been used for 45 years. One was in 1986 and has been used for 33 years.

　　Ductile iron is a kind of high strength material developed in 1950s. The manhole cover made of it has the characteristics of high strength, good wear resistance and corrosion resistance, and its designed service life is over 50 years.

　　The two manhole covers that Cheng Renbin saw were not extended service manhole covers. The staff of urban management and water affairs departments will often overhaul various manhole covers, including these two manhole covers, to find out whether they are damaged or not and whether they need to be replaced. As long as they are not damaged and they can be used safely, there is no need to replace them with new manhole covers to avoid waste.

　　Chen Zongfu revealed that some cast iron manhole covers made in the past years were of excellent quality because the manufacturers used good and sufficient materials when producing them. Moreover, they are not damaged by external forces when used, and they are well maintained, so their actual service life can be far more than 50 years, "can be used for a hundred years or even longer."