Caution: Hub ring grooves cannot have repair performed by simply skim cutting the Hub face and deepening the groove. API 16A Hub connections differ from flanges in that the ring groove, face, Hub O.D., and Hub edge width, all must conform to the exact API specified dimensions and tolerances in order to seal and function reliably. Field measurements on all of these dimensions require special tools and skills. New API monogrammed equipment has experienced careful measurement and testing by the manufacturer and only knowledgeable persons qualified to perform dimensional inspection on Hub connections should do so. Any groove rework beyond polishing must include weld repair to the Hub to provide stock for repair machining.

If circumstances require weld repair to existing used Hub connected equipment, operators should consider adding corrosion resistant material inlay to the existing Hubs at the time of repair.

If operators expect to connect and disconnect Hub connection equipment and store the equipment for any extended time, the operator would do well to specify corrosion resistant material inlay in the ring grooves at the time of original order.