Oh great, another uphole velocity (UHV) article. I first learned about UHV from a young fellow by the name of Doug Black. I had been manufacturing drill rods and accessories for 15 years, but had never delved into the use side of the business.
Doug’s presentation was about drilling 12¼-inch holes using 10¾-inch drill pipe in a blasthole situation. At 10¾-inch outside diameter (OD), the new drill pipe produced a nice feet per minute UHV. As the drill pipe wore, its diameter decreased, increasing the annulus and, thus, decreasing the UHV. Here, OD wear might determine that the drill pipe needs replacing – not because the wear is making it weak, but rather the wear reduced the UHV too much. So, in blasthole applications, UHV is important not only in the design process, but as a factor in everyday monitoring of drill pipe life.