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<br />' I`/. Actual Seaming Process <br /> A. FML material to be extrusion welded must have surface oxidation removed by lightly <br /> grinding the weld surface with a 60 or 80 grit disc. The grinding is performed parallel to the <br /> seam and controlled such that grinding marks do not extend more than 0.25 inches outside <br />' the area of the weld bead. Grinding should precede the ardual welding as Gosely as <br /> _ possible but in no case should grinding precede welding by more than one hour. Sbcty mil or <br /> thk~cer liners should have the edge of the top sheet beveled by grinding to approximatey a <br /> 45o angle. <br />' B. The FML to be extrusion welded must be temporarily bonded to hold the material in place <br />until the extrusion weld bead cools and attains full strength. This is normally accomplished <br /> by performing an automatic or hand hot air tack weld. <br /> C. The extrusion welder stwuld be purged of all degraded plastics prior to the start of seaming. <br /> D. The welding operation should be observed >b assure the weld bead is centered over the <br />' edge of the top FML sheet and that weld bead appearance is smooth and unifomr. <br /> E. All extrusion welds shoukf be non-destructively tested by vacuum testing as described in the <br /> QC Manual. Areas which cannot be non~Jestructively tested should be visually inspected. <br />' <br /> F. Destructive tests can be conducted when seam lengths are adequate. <br />1 <br /> <br /> <br /> <br />1 <br /> <br /> <br /> <br />23 <br /> <br />