Opinion ID: 384591
Heading Depth: 2
Heading Rank: 3

Heading: The Fusion Head Equipment and the Tensile Capacity of the Welds

Text: 18 The primary cause of the collapse was thus the failure of the thermal fusion (welds) of the interfaces of the styrofoam logs to have the anticipated capacity (strength) to withstand stress and tension of 27 pounds per square inch (psi). Primarily because of this failure, the dome collapsed; for the styrofoam form was unable, because of this deficiency, to withstand the stress resulting from the contributory causes that otherwise would not have resulted in the dome's collapse. Furthermore, the record reflects that the cause of the inadequate tensile capacity of the welds resulted from the deficient adjustment of the fusion head of the fabrication (spiral generation) equipment supplied by the subcontractor Dow, as a result of which, for one major defect, the calibration-adjustment did not sufficiently embed the ten-gauge wire used in this construction project. See note 1, supra. 19 The tensile capacity (strength factor) of 27 psi was not specified by the design or specifications. Tr. 59. Rather, based on past experience in using the construction process, (t)he history had been that a statistical expectation would be, as I recall, twenty-seven and a half psi in tension. Id. 20 The thermal fusion (welds) was accomplished through the fusion head of the fabrication equipment. As described by the Kidwell, the defendant's expert, in response to questioning, Tr. 187-88: 21 Q Okay. Could you explain the function of the fusion head with respect to pressure and heat in the wire and exactly how that would work in welding the logs together? 22 A Well, a heated metal plate that was called a platen was passed between two styrofoam logs. As it passed through, it groved the styrofoam logs. It fed the wires, and I believe there was four number ten wires on each side, may have been three, but I believe there was four on either side. 23 This machine fed those wires in, heated the styrofoam logs to a melted condition, just surface melting, then they were pressured, pressed together, and they would then cool and form a homogenous interface. 24 Q Which we call a weld? 25 A Which we call a weld, that's right. 26 In the inspection report following the accident, introduced in evidence as Defendant's Exhibit P, it is indicated that, while this deficient thermal fusion was present in the area of the initial fracture preceding the dome's collapse, it was not present throughout the styrofoam construction. 6 The same report indicated that, to assure proper welding, some adjustments should be made in the spiral generation equipment utilizing the fusion head. 7 Some (but not all) of these adjustments were made during the subsequent construction; no further problem in deficient thermal fusion was encountered in the subsequent successful construction of the four domes. See note 1, supra, and testimony cited therein. 27 The fusion-head thermal-fusion equipment and process had previously been used by Dow in the successful construction of smaller domes, in which slightly smaller styrofoam logs and wire had been utilized to construct the styrofoam form. The plaintiff's expert (who had been employed by the subcontractor Dow at the time of the accident) testified that he assumed that, for the present construction project, adjustments had been made to the equipment to allow for the additional tensile capacity desired, but that he did not so know from personal knowledge. Tr. 58-59. In this present construction project, during the first few rounds (at the base of the dome) an inspection was made of the adequacy of the welds by cutting into and visually inspecting the interfaces (welds) of the styrofoam logs; since these welds met the expectations of the subcontractor, no further checks (other than consistent visual inspection of the outside-beading of the logs) were made as to the adequacy of the welds during construction of the upper rounds of styrofoam bricks comprising the styrofoam dome form. Tr. 60-61. 28