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DMTech Set a New Record of ME cylinder Covers Reconditioning Numbers in July
Time of issue：
2023-08-08
DMtech Set a New Record of ME cylinder Covers Reconditioning Numbers in July
July is always a busy month for shipyard. DMtech also made a new record of ME cylinder covers reconditioning numbers in this month.
Most of them are from shipyards, for example Cosco Nantong, Nantong Ruitai, Nantong Rongshen, Zhoushan HuaFeng, Zhoushan Changhong and Jiangyin Chengxi Shipyard, some of them from the port as Nantong Tonghai Container Terminal, Port of Liangyungang & Port of Shanghai Waigaoqiao.
The 70% cylinder covers are B&W50MC/MC-C/ME type. For B&W 50MC/ME type cylinder covers, the reconditioning items usually are sealing grooves,landing face, pocket for Exh V seat, fuel injector holes , indicator hole, starting valve pocket.
Here we analysis some special cases.
Case 1--The technician found one cylinder cover, the cracks around the fuel injector is not normal. The cracks is on the sector of anti-corrosive material area. Usually the crack is coming from the edge of fuel injector hole. DMtech technician judged it probably was caused by welding. It’s right, the cracks inside the welding lay was found after handing gorging. There are slags inside as last reconditioning, it means the welding quality leads to the cracks.
Case 2--We always find through cracks on the sealing grooves and landing face. The through cracks caused leakage in the sealing grooves. The shipowners would like to think it’s management and maintain problem. We do not think so. Our opinion is the design defect leads to the cracks. We find the angle under the landing face is too small, sometime almost 90 degrees, where the casting stress can not be released properly.
Below Type A always finding cracks. Type B is modified and better than Type A. Type C improves obviously.
The point is cracks should be cleared thoroughly and the annealing must be carried out to release the welding stress. It is very important for qualified reconditioning and to get a longer service life.
We may modify the shape of the cooling water chamber, to make a bigger angle to avoid the centralized stress, according to owner’s request.
There are many type of B&W 50MC/ME cylinder covers, because of the difference of total height, the out-shape, the sealing grooves and fuel injector dimension. The 50MC/ME cylinder covers came from 8 vessels and met to 6 drawings this month. The inspector should be very careful to get the dimension and submit the sketch to latheman. Anyway most of DMtech technicians have been working in the reconditioning industry more than 15 years, they know why profoundly and know how perfectly.
Hot July and lot orders did not delay our delivery. So passionate a July!
盛夏七月，如火如荼。
南通迪赛生产车间繁忙有序，主机缸盖修理创新单月最高纪录。分别来自修船厂，如中远南通船务，南通瑞泰船务，舟山华丰船厂，舟山长宏国际，江阴澄西船厂等。还有来自港口码头，如南通通海集装箱码头，连云港新路桥码头和上海外高桥二期等。其中船厂工程有两条船6缸全部翻新。
七月主机缸盖翻新中，机型B&W50MC/ME占70%。50MC缸盖吊缸拆解后修理项目，主要集中在密封槽腐蚀、阀座装配密封面腐蚀，也有部分缸盖出现油枪孔吹蚀及裂纹，示功孔、启动阀孔裂纹等。这些问题在50MC主机缸盖中较为常见。在此重点解析一下B&W50MC/ME缸盖翻新中碰到的几个特别案例，共同学习和探讨。
案例一：如图某船下来一只缸盖，其他部位状况较好，主要是油枪孔裂纹，应该是装机使用时间不长。
原因分析：1、油枪孔产生裂纹，一般由于高温燃烧，在喷油器喷油方向成规则吹蚀，继而在孔边开始出现裂纹，并向孔内和孔外延伸。2、此缸盖裂纹比较特殊，仔细观察发现，裂纹不是从油枪孔边缘往上延伸，而是直接出现在之前堆焊的耐蚀合金部位。由此判断，此裂纹的发生应该与上次翻新厂家烧焊质量相关。手工碳刨后，发现不熔合现象，焊层中有夹渣，高温之后，内部产生裂纹并延伸到表面。
针对此情况，我们组织焊工现场学习，并由资深焊接专家传授经验，分析为什么会产生此类情况及如何避免。
案例二：翻新过程中也经常碰到在密封槽和密封面处出现贯穿裂纹现象。这次有一条船的缸盖出现此类情况。南通迪赛曾经承修过这条船的姐妹船，其缸盖也多次出现贯穿裂纹。许多机务和老轨经常有疑惑，为什么会出现这种贯穿裂纹。船东公司也怀疑是否为保养和管理的问题。
原因分析：经过长期观察和总结，我们认为出现贯穿裂纹的缸盖多为设计上的缺陷导致。主要是冷却水槽过深，过渡角度太小，接近90度。导致应力集中，从而容易在此位置最先出现裂纹。对比相同机型，有的设计过渡角度明显大得多，基本上未发现过些类贯穿裂纹。如下图TypeA很容易导致贯穿裂纹，TypeB有所改进,TypeC则是明显改进，已经基本上看不到角度了。B&W35MC/ME也有类似情况，我们曾按照船东要求，对其进行了改型处理，后续使用效果正在观察中。此次有国外船东提出改型要求，我们将持续跟踪使用状况。
修理经验总结：
1、B&W50MC/MC-C/ME虽同为50机型，但是因为高度、外型、及其他关键尺寸的差异，需要在预检时就进行仔细比对，既要参考原始图纸，但是又不能拘泥于图纸数据，还需根据所修工件进行不同应对。
2、此次集中修理的50缸径缸盖，分属8条船，适用6张图纸，对工艺和生产提出严峻考验。我们生产人员本着“我严谨、您放心”的一贯作风，一丝不苟地分析分类，冷静细致地判断比对，确保加工尺寸精确，确保修理工艺到位，确保装机试机一次成功。
3、缸盖的集中修理，也给我们创造了一个转变生产思路的机会，结合实际，转变生产模式，把单件修理转变成批量生产，提高了效率，增强了工效，满足了船东对交付工期的要求，得到船东的认可和称赞。
特别感谢船东、船厂的信任，我们将一如继往地坚持“我严谨、您放心”，质量事故零容忍，诚信服务贯始终，不断提高服务船东的能力。
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Diesel Maritech Nantong Co.,Ltd
Add:No.129, Xinsheng Road, Nantong
Contact：Ron Cheng Ligang Yu
Mobile：0086-13776909006 15370660922
Email：sales@dmtechnantong.com
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