The Stoomwezen piping code has a number of differences from the B31 piping codes. For instance:
- The Stoomwezen code addresses mill tolerance in the flexibility analysis, whereas the B31 codes do not.
- The Stoomwezen code has some minor differences in the SIF computations.
- The Stoomwezen code determines allowable stresses based on both yield and creep properties of the materials, while the B31 codes don't.
This is by no means an extensive list of the differences. You should really get a copy of the code and go through it yourself. This is the only way to pick up the details and nuances.