Manufacturers provide specifications for their belts that include allowable tension Fa
(or stress σall), the tension being expressed in units of force per unit width. Belt life is
usually several years. The severity of flexing at the pulley and its effect on life is reflected
in a pulley correction factor Cp. Speed in excess of 600 ft/min and its effect on life
is reflected in a velocity correction factor Cv . For polyamide and urethane belts use
Cv = 1. For leather belts see Fig. 17–9. A service factor Ks is used for excursions of
load from nominal, applied to the nominal power as Hd = HnomKsnd , where nd is the