b'TECHNICAL & RESEARCH Continued from page 11Figure 13. This machine is a robotic, automatic seam welder gun and a hand welder. Field seams on this project will need be thoroughly probed.Otherfactorsthatwill affectfieldseam-welding qualityaresunlight,wind, shade, ambient temperature, andhumidity.Itisimper-ativethatthedesignatedFigure 14. Comparison of welds. From le to right: poor weld, incomplete weld, and good weld.roboticwelderoperatoris thoroughly trained and familiar with the equipment being used. Roof manufacturers recommend that the subcontrac-tor perform test welds before welding actual \x17eld seams.^ilely memrae Test welds consist of the following steps:1.Set up the welder temperature and speed.2.Perform test welds with scrap material. are eile a eeriee 3.Allow the test welds to cool and then attempt to pull them apart in a peel action.yami moveme ri A good weld will be demonstrated by the exposure a solid 1.5- to 2-in.-wide (38- to 50-mm) area of reinforcing scrim, as shown in the scrim on the right side of Fig. 14. Iteir lie a \x04 e is important for the designated welder operator to perform these test welds each time they start up the equipmentmemrae aro e and aer the equipment has achieved the operating tem-perature. The time of day, direct sunlight versus indirect sunlight (shade), high winds, or cloud cover versus sun- rae ea a shinecanallaectthetemperature,speed,andoverall weld quality.Hand-welding seams and ashing details are at leastora, e rae as important as, and oen more important than, robotic seam welding. The hand-welding-detail roof techniciansa eerae ro e mustbewelltrainedandexperiencedintheuseofa hand welder. Hand welding requires a great amount of patience and skill. It cannot be rushed, as any attempt atreioreme a oom expediting the process can result in poor welds, which can permit moisture intrusion into the roof assembly. Figure 14 provides an example of a poor (cold) weld. A cold weldlayer o memraemay visually appear to be a good weld/splice, but minimal pressure from a seam probe or wind can cause a cold weld to open and fail.12 www.mrca.orgMidwest Roofer41'