Specifications include, but are not limited to: procure two (2) packaged, flexible water-tube boilers complete with trim and accessories as specified herein. ; The rear target wall shall be of industrial grade heavy-duty construction. Wall shall be constructed of no less than 4” of 1900 deg. F insulating poured refractory, 1” of high temperature mineral board and 4” of 2700 deg. F castable refractory. The high temperature refractory shall have no contact points with the boiler furnace wall steel. ; Boiler inner casing shall be fabricated of not less than 11-gauge reinforced steel. Entire boiler casing shall be comprised of “bolt on” type panels. ; Boiler outer jacket shall be constructed of 20-gauge insulated steel panels. Overall boiler inner / outer housing design shall allow for a two (2) inch insulating air space between the inner and outer panels.