The issue of the difference between the valve flange diameter and the inner diameter of the steel pipe

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This post was last edited by cjgj008 on 2018-8-5 at 23:52. I have an amateur question; please don’t laugh at me, fellow sailors. We recently carried out a process modification; one section of the pipeline consists of seamless stainless steel pipes with DN150, PN16 specifications. According to the design drawings prepared by the design institute, the flanges used are of type A from the PN series as specified in HG/T20592, and the steel pipes correspond to type A (Series I) with dimensions of 168*5. As a result, the inner diameter of the pipeline is approximately 158 ； The ball valve on the corresponding pipeline has flanges specified as DN150, PN16, with full bore; it has already been purchased. The inner diameter of this valve is around 150, which differs from the pipeline’s inner diameter of 158 by approximately 8 to 10 mm. Since our process involves using balls to clean the pipes (hard balls, sized according to the inner diameter of the pipes with a slight excess), we are concerned that the valves might become a bottleneck when the balls are used for cleaning the pipes, potentially trapping the balls. If the sphere is reduced in size, there is a concern that the pipelines won’t be cleaned thoroughly. I would like to ask fellow sailors: what should be done in this situation? Is it my understanding of the standards that is wrong? Should the requirements regarding the diameter be clarified with the manufacturer during the valve procurement process?