Reducing insert flanges have the same size requirements as standard jacketed piping; the backing flange size matches the nominal size of the jacket pipe. This requires equipment that must mate with the reducing insert flange to have oversize flanges.
Non-reducing insert flanges are sized to match the core pipe and allow the use of core-sized equipment. In this regard, non-reducing insert-flanged jacketed piping is similar to swaged jacketed piping; but unlike swaged construction, non-reducing insert flanges enable back-of-flange heating for more uniform temperature control.
Due to its smaller size, the non-reducing insert flange demands more dexterity of installation personnel than does a reducing insert flange. For this reason, many designers specify reducing flanges on pipe-to-pipe connections and non-reducing flanges on pipe-to-equipment connections.