Abstract: For determining the adequate perviousness of venting tube nipples (4) on fuel tanks (3) made of plastics material a test duct (12) is connected to the nipple (4) and air drawn into the test duct (12) from the tank (3). From measuring, the partial vacuum of e.g. approx. 5 mbar or the volume flow rate in the test duct (12) it can be determined whether the nipple (4) and its joint (9) to the tank (3) are sufficiently permeable. This test is very precise and silent and needs only little consumption of compressed air. Thereby the load on the sealing seat (14) between test duct (12) and nipple (4) is only slight.

Abstract: For joining two faces (41, 42) of thermoplastics in a penetration beam welding method the covered face (42) is multiply scanned and thus incremently heated by a laser beam (10) directed through the covering face (41). This preheating is repeated until the melting temperature is attained. In the region of the covered face (42) a melt thus materializes simultaneously over the full seam length which wets the covering face (41) and thus also transfers this face into melt by heat conduction. On completion of material softening the faces (41, 42) are mutually moved until abutting. Thus the two faces (41, 42) weld in principle as if they had been plasticized simultaneously over the full seam length which significantly enhances the seal and strength of the seam, whilst the expenditure the apparatus is low.