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<br /> <br />The colder the weather, the slower the welding speeds possible for effective <br />welding. Further detail for cold weather welding follows this section. <br />In all cases, the geomembrane shall be dry and protected from wind. <br />ILPI shall verify that these weather conditions aze fulfilled and will advise the Project <br />ivlanager if they aze not. The Project iVlanager shall then decide if the installation shall be <br />stopped or postponed. <br />Sold Weather SeamirU of Polvzt vlene Liners <br />Cold weather welding restrictions exist because problems associated with hot air seaming <br />techniques have been mistakenly applied to other types of welds. The extrusion weld, <br />however, has been successfully employed in cold weather on many job sites. With the <br />assistance of preheating the sheet, the extrusion weld has been applied as low as -5 <br />degrees Fahrenheit. Both the extrusion weld and hot wedge weld aze able to overcome <br />cold weather welding restrictions because of their unique designs. <br />The extrusion welder is capable of continuously monitoring and controlling [he <br />temperatures of the extrudatz and the zone of contact for independence of environmental <br />conditions. To control the molten bead temperature accurately and to ensure no <br />fluctuation out of the predetermined range the machine has: <br />a. ~n over capacity heater band on the extruder. <br />.4n extra over capacity heater band on the nozzle. <br />A separate proportional temperature controller for each heater band. <br />d. The nozzle thermocouple positioned approximately'/s inch from the end of the <br />nozzle which rides on sheet. <br />The hot wedge weld lifts the sheet slightly to minimize the effects of subcooling from a <br />frozen sub-base. In addition, a hot air blower can be used to preheat the sheet in the path <br />of the hot wedge. Temperature controls can be adjusted to guazantee fully integrated <br />welding as demonstrated by peel testing. <br />To guarantee quality welding in cold weather, the following procedures aze recommended <br />for ILPI welds: <br />The sheet should be preheated before welding any time ice crystals aze present in <br />the weld path. <br />When strong winds aze present, a shield of some sort should be set in place to <br />prevent convection heat losses from the welding machine during seaming. <br />IS <br />