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24 25 seaming, and location of thermocouple within the device . It is necessary for the operator to keep constant visual contact with the temperature controls, as well as the completed seam exiting the welder to ensure adequate welding is occurring . It is not recommended to adjust welding parameters without the approval of a trial seam (See section 3 .01 .D .1 below) . Pre-heating of the geomembrane in the seaming area is optional . The amount or type of preheating and its timing preceding the actual seaming is at the option of the installer . Properly functioning portable electric generators must be available within close proximity of the seaming region and with adequate extension cords to complete the entire seam . These generators should be of sufficient size or number to handle all seaming electrical equirements . The generator must have rubber tires, or be placed on a smooth plate such that it is completely stable and it does not damage the geomembrane . Fuel (gasoline or diesel) for the generator must be stored away from the geomembrane, and if accidentally spilled on the geomembrane it must be removed immediately . The areas should be inspected for damage to the geomembrane and repaired if necessary . Field Tape Seaming Prepared tapes include mastics, putties, asphalt, and butyl tapes can be used to seam some geomembranes . Selection of the tape depends on the material being seamed and the fluid being contained . Immediately after creating a tape seam, it should be loaded or secured to facilitate bonding . The preferred method for securing prepared tape joints is to backfill the geomembrane with a suitable soil cover so tensile stresses do not develop . The backfill creates a pressure seal between the geomembrane panels and tape which is usually effective . An alternative method of creating strength in a tape seam is to sew the seam first and then use prepared tapes to waterproof the joint . Even with a sewn seam; the recommended practice is to backfill the geomembrane to prevent shifting of the seam and to help adhere or bond the tapes . The minimum overlap of geomembrane sheets for tape seaming shall be about 0 .10 m (4 inches) . Snow accumulations must be removed prior to seaming because tapes may not adhere or stick in the presence of frost or dew . To create a tape seam, place one or two continuous lines of prepared tape between the sheet overlap . Press the sheet materials together to compress the tape using a rubber hand roller or similar tool . In areas where wrinkles cannot be removed, use tapes on all sides of the wrinkle to form a waterproof seal . Visually inspect the completed seam to ensure intimate contact between the tapes and the upper and lower sheet surfaces . Repair discontinuities by placing a patch over the damaged area with a prepared tape seal around the perimeter . The patch must be round, oval, or contain rounded corners and extend 0 .15 m (6 inches) around the defect . Supervise the backfilling of the seam area to prevent the seam from being pulled apart . Backfill should proceed in a direction that does not tend to pull the seams apart or create a shear or tensile stress in the seam . Field Seaming Test Requirements Test Seams (Trial Seams) Test seams shall be prepared and tested by the Geomembrane Installer to verify that the seaming parameters are adequate at the start of each welding session or at the beginning of each working day .Test seams also may be made whenever personnel or equipment are changed and when climatic conditions reflect wide changes in geomembrane temperature or other conditions that could affect seam quality . A minimum of one test strip per seaming apparatus shall be conducted at the start of each welding session during a day and at least every 4 hours or 3000 lineal feet of field seam per machine, whichever is more frequent . Test seams shall be made using “scrap” material from the same lot as the geomembrane being welded in the field because the geomembrane is pre-fabricated into panels in a factory . This requirement is necessary to ensure that the installed geomembrane panels are not damaged prior to the onset of the field welding process because no destructive seam tests shall be conducted on field welded seams to preserve integrity of the fabricated panels . The test seams shall be at least 1 .8 m (6 ft) long for all types of field seams . If there is no area or equipment on site to provide for these seam requirements, seam strength can be verified for production using trial welds sent to an independent testing laboratory to verify properties . If a test seam fails, an additional test seam shall be immediately completed . If the additional test seam fails, the seaming apparatus shall be rejected and not used until the deficiencies are corrected and a successful full test seam is produced . Each test seam shall be labeled with date, geomembrane temperature, weather conditions, number of seaming unit, panel identification, seam number or test location, technician performing the test seam, and a pass or fail description . Pre-qualification seams for tape seams shall be in accordance with ASTM D7272 . Non-Destructive Testing (NDT) of Seam Testing All Field Seams shall be non-destructively tested by the Geomembrane Installer over the full length of the seams before the seams are covered . Each seam shall be numbered or otherwise designated . The location, date, test unit, name of the technician, name of QC person, and outcome of all NDT shall be recorded and submitted to the Owner’s Representative . Testing should be performed as the seaming progresses, not at the completion of all field seaming, unless agreed to in advance by the Owner’s Representative . All defects found should be repaired, re-tested, and remarked to indicate acceptable completion of repair . NDT shall be performed using one or more of the following methods: Air Lance Testing (ASTM D 4437) The Geomembrane Installer shall provide an air compressor, air hose, and air lance wand with a pressure gauge capable of measuring air flow to the tip . The testing shall be performed by experienced technicians familiar with this testing procedure . This non-destructive test involves placing the air lance wand 6 to 12 mm (1⁄4 to 1⁄2 inch), but not more than 50 mm (2 inches), from the edge of a completed seam and closely monitoring the backside of the sheet for any air penetration through the seam, loose edges, riffles, and/or noise . If air penetrates the seam area, the technician will either see this visibly or hear it audibly and the area shall be marked for repair . Mechanical Point Stress or “Pick” test (ASTM D4437) This NDT uses a dull tool (such as a blunt screwdriver) under the top edge of a field seam . With care, an installer can detect an un-bonded area, which is easier to separate than a properly bonded area . Care should be taken to not damage the already bonded areas . This method must be used with extreme care so as not to damage the parent thin gauge geomembrane and is to be used only if other NDT methods are not available . Installation Instructions Page 5 of 9 Installation Instructions Page 6 of 9 InterWrap.com CANADA | USA | EUROPE | INDIA | CHINA CANADA | USA | EUROPE | INDIA | CHINA InterWrap.comPDF Image | GEOMEMBRANES
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