Depending on the distance, one or more transitional idlers should be used to support the belt between the terminal pulley and the first fully-troughed idler.
It is good practice to install several transition idlers supporting the belt to gradually change from a flat profile to a fully troughed contour. Transition idlers can be manufactured at specific intermediate angles (between flat and fully troughed), or they can be adjustable to fit various positions. For example, it would be good practice to place a 20-degree troughing idler as a transition idler forward of a 35-degree troughing idler, and both a 20-degree and a 35-degree idler in front of a 45-degree idler. CEMA recommends that all transition idlers use metal rollers.
Track-mounted designs allow idlers to be serviced much easier.
It is also important to the stability of the belt and the sealability of the transfer point that the transition idler closest to the terminal pulley be installed so the top of the pulley and the top of the idler’s center roll are in the same horizontal plane. This is referred to as a full-trough transition.