The present study reports the design and safety analysis of high pressure mechanical milling vials designed for the direct synthesis of high capacity metal hydrides. The theoretical calculations and the simulation studies reveal that the load applied at 120 bar inner pressure is only one third of the sustainable load capacity of the milling vials. The advantages offered by direct synthesis of high capacity hydrides such as, MgH2, KAlH4 and NaAlH4 at high pressures were demonstrated by ball milling the reactants Mg + 0.03C, NaH + Al + 0.03TiF(3), KH + Al + 0.03TiF(3) at the hydrogen pressures, respectively, 30, 60 and 100 bar in the designed vials. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.