instant invention can best be seen the elbow fitting is intended for use in a pneumatic product conveying system utilizing only the dilute and intermediate phases of conveying by connecting to a conventional inlet pipe not shown and an outlet pipe not shown to provide a directional change for the path of travel of the product within the pneumatic system the operation and general structural details of the expanded elbow fitting are disclosed in u s pat no 6 951 354 issued to jerome i paulson on oct 4 2005 and in u s pat no 7 300 074 issued to jerome i paulson on nov 27 2007 the contents of both issued patents being incorporated herein by reference in their entirety the elbow fitting 10 is preferably formed from a durable metallic material such as aluminum cast iron or stainless steel and includes an inlet portion 16 and an outlet portion 17 each of which are sized to mate with the inlet pipe not shown and the outlet pipe not shown in a known manner such as through a known compression coupling not shown between the inlet portion 16 and the outlet portion 17 the elbow fitting 10 includes an inlet transition section 18 and similar outlet transition section 19 connected respectively to the inlet portion 16 and the outlet portion 17 lastly a curved expanded section 12 interconnects the inlet and outlet transition sections 18 19 the inlet and outlet transition sections 18 19 transcend between a circular cross section of the inlet and outlet portions 16 17 and a generally triangular cross sectional configuration of the curved expanded portion 12 the triangular shape of the curved expanded portion 12 generally carries through the curved expanded portion 12 except as required to curve.