#The only situations where It is advisable to use eccentric reducers are for slurry systems and where it is imperative to totally drain ALL condensed fluid. In both these situations, eccentric reducers can avoid small "dead spots" that exist behind concentric reducers. The only place I'd use flat side up eccentric reducers would be in pump suction line to avoid accumulation of gas pockets.
#The general recommendations, from a process point of view, to avoid adversely altering the CV characteristics and capacity are:
1. Avoid arrangements that can result in a nozzle-effect into the CV
2. Avoid closed-coupled inlet block valves reduced from line size
3. Avoid contorted manifolds to achieve accesibility, in particular in block-and-bypass arrangenments
4. Use straight-line pipe sections into and out of the CV as needed for the CV, as originally established by the control engineer. A ROT for reducers and expanders: 12
nominal pipe diameters (NPD) upstream and 5 downstream. For elbows on the same plane 18 NPD upstream, 30 NPD if not on the same plane.