Still associated with the case presented in the previous article, Process Performance(for example the case of reducing the leakage of oil), Fish Bone diagram will facilitate the search for problems that cause oil leakage. This is an analysis process to determine in detail the roots of the problems occurred. The following image is a simple example to find the cause of the problem. Causes of the search there are two root root causes can be identified that Black light inspection procedures are not appropriate. And insufficient hydrostatic test pressure has been running during the process.