According to the properties of powders and the operating conditions, arching in a standpipe with negative pressure gradient has been classified into two types, bubble arching and particulate arching. The model for predicting the width of particulate arching presented in this paper is confirmed by measuring the width of the static arching in hoppers connected to a standpipe with negative pressure gradient, and the effect of various factors, such as the flow functions of the powders, the operating conditions, and the time of consolidation, on the width of static arching is discussed in detail. A method is presented to determine the minimum size of the outlet of a hopper connected to a standpipe for the design of an industrial standpipe.