Instances where this may occur include tight radius bends, partial blockages and areas downstream of partially-throttled valves. As velocity increases, shear stress increases until the stress is such that it damages the protective film. Efird studied and estimated the critical shear stress for various alloys. Shear stresses exerted vary with velocity and geometry as indicated by Figure 7 . As pipe diameters increase, copper-based alloys tolerate higher nominal velocities.
More work is necessary to explain the full extent of hydrodynamics on a flow system.
Other copper-nickel alloys have been developed and found to offer even better resistance to impingement attack.