As part of the continuing effort to establish design parameters of lock hoppers for the handling of coal, engineers at Jenike and Johanson, Inc. have run a series of tests on an 18 inch diameter lock hopper system. The purposes of the test program are: to establish the theoretical basis for predicting the flow rates from lock hoppers, to test a new concept of an acceleration section below the hopper outlet to minimize valve size, to evaluate a new cone-in-cone design used to reduce head room requirements for lock hoppers and to determine the effect of initial pressurization of the lock hopper on the subsequent flow of the bulk material during discharge. Results are discussed. 11 refs., 12 figs.