The coefficient of dynamic friction is a measure of the friction between a moving cable and the conduit. The coefficient of friction can have a large impact on the pulling force calculation. It can vary from 0.1 to 1.0 with lubrication and can exceed 1.0 for unlubricated pulls. Pulls should never be stopped and restarted because the coefficient of static friction will always be higher than the coefficient of dynamic friction.
The coefficient of friction between a cable exterior (jacket/sheath) and conduit varies with the type of jacket or sheath, type and condition of conduit, type and amount of pulling lubricant used, cable temperature, and ambient temperature. High ambient temperatures can increase the coefficient of dynamic friction for cable having a nonmetallic jacket.
Pulling lubricants must be compatible with cable components and be applied while the cable is being pulled. Pre-lubrication of the conduit is recommended by some lubricant manufacturers.