Abstract: A belt conveyor includes an assembly of conveyor idler rollers for supporting a conveyor belt advancing thereon. Each conveyor idler roller includes a cylindrical body that is freely rotatable about a shaft. A keeper seal prevents axial displacement of the cylindrical body along the shaft and inhibits foreign matter from penetrating into the central opening of the cylindrical body. The keeper seal comprises a radially projecting collar at the proximal end of the shaft which mates with a radially projecting groove formed in the cylindrical body to prevent axial displacement of the cylindrical body along the shaft and to inhibit foreign matter from penetrating the central opening of the cylindrical body.