I have route a 4" pipe. When i generate a iso using isogen, the pipe size is written as 2581NS. Thats like (4"x25.4x25.4). It seems like the pipe size was converted to MM and then try to convert it again. I wish to remain the pipe size in imperial unit since direct conversion does not result in DN. Would appreciate if someone can enlighten me on how to solve this issue.
What type of units have you defined for your project ?
You are able to define units when you create a new project, imperial size and dimensions / metric size and dimensions / imperial sizes and metric dimensions. I doubt the last option works.
If you use ASME catalog in Metric project you will get a direct conversion and will end up in nominal sizes like 102, 203,.... to have nominal sizes like 100, 200 shown on ISOs you should use DIN catalog.
Generally there is a bug in this version of P3D regarding imperial/metric units.