It is interesting that the terminolgy changes from the 'Shall' stated in regards to the WFS being installed on top of the pipe, to using 'Should' for the clearance fro valve/fitting.
And then you have the likes of this
My understanding is that since the manufacture has received approval based on this arrangement that it is ok to have the WFS basically right beside the valve/drains/fittings.
To be honest seeens a bit 'bogus' that the manufacturers of these Riser Control Assemblies can get approval for the WFS close to the Valve/Drain but the WFS manufacturer can't.(?)
Posible that the term 'should' was chosen over shall to allow for these type assemeblies.(?)
Also, while having the conversation

,as you mentioned there are some projects that the Engineer can specifiy to reduce the velocity in risers to comply with the maximum allowable surge stated on the datasheet. However, since this is stated on the manufacturers datasheet, with the same theory that the manufacturers recomendations become requirement for installation, then it would seem that even if the engineer has not specified a restriction on the velocity in riser, that the restriction still exists by way of the datasheet, and therefore should be standard practice anyway. (I don't usually see this happening).
Thoughts?