Method of assembling a boiler unit having pre-assembled walls

A method of field erecting walls of a boiler unit at a job site comprising:

• assembling a plurality of membrane wall modules at a point of shipment which is separate from the job site, each module including a membrane wall containing a plurality of membrane wall tubes connected to each other by membrane bars, a plurality of buckstays connected to the membrane wall, insulation covering one side of the membrane wall and lagging covering the insulation thereby forming an assembled membrane wall module;
• shipping each assembled membrane wall module to the job site;
• attaching at least one temporary beam to the buckstays of each assembled membrane wall module for limiting deflection of each assembled membrane wall module when said assembled membrane wall module is lifted;
• lifting each assembled membrane wall module by at least one temporary beam connected thereto, into a vertical position thereby forming vertically positioned modules;
• welding adjacent vertically positioned modules to each other thereby forming the walls of a boiler unit;
• and
• removing the temporary beams from the walls of the boiler unit.