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~~ <br /> <br />For fusion welding, a movable protective layer of plastic may be required to be <br />placed directly below the overlapped membranes being seamed. This is to <br />prevent any moisrure buildup benveen the sheets to be welded and/or to provide <br />consistent rate of speed for the wedge welding device. <br />3.3.7 Nondestructive Seam Continuity Testing <br />3.3.7.1 Concept <br />ILP[ shall non destructively test all field seams over their full length using a <br />vacuum test unit, air pressure testing, or other approved method. (Vacuum testing <br />is described in Section 3.3.7.2 and air pressure testing is described in section <br />3.3.7.3). The purpose of nondestructive tests is to check the continuity of seams. <br />It does not provide information on seam strength. Continuity testing shall be <br />carried out as the seaming work progresses, not at the completion of all field <br />seaming. <br />3.3.7.2 Vacuum Testing <br />The equipment shall be comprised of the following: <br />A vacuum box assembly consisting of a rigid housing, a transpazent <br />viewing window, a soft neoprene gasket attached to the bottom, port hole <br />or valve assembly, and a eauge to indicate chamber vacuum; <br />A pump assembly equipped with a pressure controller and pipe <br />connections; <br />A rubber pressure, vacuum hose with fittings and connections; <br />A bucket and wide brush or spray assembly; and <br />A soapy solution. <br />The following procedures shall be followed: <br />Energize the vacuum pump and reduce the tank pressure to approximately <br />5 psi (10 inches Hg.); <br />Wet a strip of geomembrane approximately 12 inches by 24 inches (0.3 m <br />by 1.2 m) with the soapy solution; <br />Place the box over wetted azea; <br />Close the bleed valve and open the vacuum valve; <br />20 <br />