Joining metal tubes by concentric socket ends with internal lip cover - the cover pref. being of nylon 11 or 12, to form a trapped seal

摘要

Metal tubes are coupled by forming 'tulip' (socket) ends such that the smaller can enter the larger, after being filled with a double sided cover, and the mouth of the larger end can then be crimped behind the shoulders of the smaller end to secure the joint longitudinally. Suitable for small bore pipes of steel or ductile metals, esp. if having an internal protective coating of matl. such as PTFE which would be damaged by local brazing or welding. Pref. the tulip ends each have a conicity of 5-30, pref. 10-15 deg. and a length of 1-1.5 times the tube dia., the larger tulip being longer than the smaller. Pref. joints are where the double sided cover fitted over the end of the smaller tulip, to provide the seal, i.e. of nylon 11 or nylon 12, though covers of natural or synthetic rubber or of a fluorocarbon or silicone polymer may also be used, depending on the pipe contents in service. Opt. the end surfaces of the smaller tulip are lubricated to assist fitting of the cover.