A glass manufacturing apparatus may include a portion of a conduit positioned within an internal bore of a refractory tube. In one embodiment, the refractory tube includes a first heating element operable to heat a first length of the refractory tube and a second heating element operable to heat a second length of the refractory tube. In another embodiment, a forming vessel includes an inlet and a lower end of the refractory device is positioned within the inlet. In further embodiments, methods of manufacturing glass include flowing molten material along the flow axis through the interior pathway of the conduit. In some embodiments, the method includes flowing molten material through an outlet of a downstream segment of a delivery pipe positioned within the inlet.