The Penflex Corrugated Metal Hose and Braid Specification Guide refers to Centerline Bend Radius as either “Dynamic” or “Static”.  What is the difference?

These two words describe the movement of the hose assembly after it is initially installed.  A hose which is installed to take-up a misalignment between a piece of equipment and the piping system outlet, for example,  may be bent upon installation but after that it will not move again.  It will remain STATIC.  Bending the hose to this small radius may result in a permanent “set”, but if the hose will remain in this position, this is not a problem.  On the other hand, some hoses are used to accommodate movements which take place repeatedly throughout the life of the hose.  These hoses are bent as they are installed in one configuration, but later the position of one end of the hose may move so that the shape of the hose changes to another configuration.   This hose is DYNAMIC after it is installed.  As the hose shifts from one position to the other, areas along the “curving” sections experience relative movements of the corrugations “compressing” on the inner sides of these arcs and “extending” on the outer sides of the arcs.  The smaller the bend radius, the more deflection and stress at each corrugation.  For this reason, a larger bend radius is recommended when repeated bending stress is anticipated.