The OHTE experimental device was designed with five distinct modules with the idea of assuring flexibility during initial construction and later maintenance activities. Experience over the last two years has proven the value of this approach in maximizing experimental time. Construction and major upgrade activities were accomplished in shorter times because the work on the various modules was done in parallel. Moreover, the efficiency of these activities was increased because the subassemblies were located at several on-site facilities where additional equipment, work space and personnel were available. Downtimes during minor maintenance activities have been minimized because disassembly and reassembly of the modular machine can be accomplished in a matter of days.