Users often forget, for example, to change the cartridges of the filters in good time, or designers select hoses with insufficient internal diameters. As the hose length increases, the flow resistance becomes higher and the flow resistance is an important parameter in a vacuum circuit (see also Section 5).
In addition, particularly in dynamic applications, flexible hoses (e.g. polyurethane) must be used and the hoses must be secured with union nuts (for small hose diameters) or hose clamps (for larger diameters).