Inside scaffolding for large metallic structures and method of using same

Removable scaffolding structure for constructing a spherical tank from metallic plates which comprises a free-standing central tower which is divided into a plurality of detachable sections that are aligned one section atop another and which tower contains equipment for the welding of the spherical tank, the lowermost section of said central tower being supported in base means that is fixed to the ground, each said detachable section being supported in turn upon the next lower section of said tower, radially extendable passageways connected to several of said tower sections by hinges at one end thereof, which passageways are each divided into at least two sections that are mutually displaceable, and stays connected to each of said passageways at a location spaced from said hinged end and to an upper location on said tower so as to support said passageways in working positions during welding operations in the construction of the spherical tank, said welding equipment including supply conduits for welding operations, which conduits are connected to corresponding plugs at the outside of the spherical tank structure through said base, connections between said supply conduits being made at each junction between said detachable sections and working connections to each of said supply conduits being provided as a part of each section of said tower which carries passageways, whereby after the completion of the welding operations, said passageways are pivotable about said hinges to be folded back to lie against said tower section to which each passageway is hinged, allowing each of said tower sections including the welding equipment contained therein to be withdrawn sequentially from the structure through an orifice of relatively small diameter which is left in the top of the spherical tank.