b'Heat-welded thermoplastic field seamsInmyexperi-ence,theprocedure to heat-weld thermo-plasticfieldseams has several important steps.Thegenerator usedtopowerthe roboticseam-weld-ingequipmentisof utmostimportance andmustmatchthe continuouswattage outputrequiredin theweldermanufac-turersspecifications Figure 11. Damage and marks from loading activity. (seeFig.12).This generatoralsomust not be used to power Some means of protecting the roof assem- roofmembraneaswellascutsandpunc- any other equipment while it is powering the bly from damage should always be in place attures.Thesescratchescangroworexpandrobot welder. Additional power drain on the loadingareas.Looselaidinsulationcoveredthroughexpansionandcontractionforcesingenerator by hand welders, screw guns, or other with plywood or similar is a good protectivefreezing-and-thawing cycles as well as normalelectrical tools could cause power surges and measure. Plywood sheathing over a slip sheetexpansionandcontractionwithtemperaturepower drops, which can be detrimental to field or extruded polystyrene insulation board mayfluctuations.Single-plymembranesareflexi- seam-welding quality (see Fig. 13). The spec-be used. ble and experience dynamic movement duringification on the continuous wattage varies by However,wehaveallbeeninsituationstheir life spans. As the membrane around thewelder manufacturer. Please refer to the welder where protective measures were not taken. Inscratches expands and contracts, the scratchesequipmentmanufacturerstechnicaldatafor thesecases,therecanbevisualevidenceofcan penetrate through the reinforcement andspecific generator wattage requirements for hot-damage on the roof membrane such as scratchbottom layer of membrane. air welding equipment.marks, punctures, debris, inden-tationsintotheroofassembly, damaged flashings, and crushed insulation.Thisdamageshould be marked, dated, and temporar-ily repaired when found (see Fig. 11).Permanentrepairsshould becompletedoncetheclient, owner, or general contractor has determined that all loading and unloading activity has ceased.Mostcommercialroofing manufacturersspecify that no morethan10patchesshould beinstalledinanyoneroofing squareor100ft 2(9.3 m 2 )area. When more than 10 patches are locatedinany100ft 2(9.3 m 2 ) area,onelargepatchmustbe installed to cover or replace the damage. The decision whether to repair, cover, or replace damaged membrane depends on the sever-ity of the damage, as defined by the roof manufacturer.Itisrecommendedto repairscratchmarksintheFigure 12. A 12k generator being used for a robot welder and a screw gun.40www.mrca.orgMidwest Roofer 11'