Boiler tube cylindrical boss - has similar concave recesses at each end to avoid incorrect assembly

摘要

The cylindrical bosses are for fitting to boiler tubes, particularly those of combustion chamber walls, and are recessed at their ends towards the tubes or mountings. The bosses (7) have similarly-shaped concave recesses (6) at both ends. The design simplifies loading of welding pistols securing new bosses in places where the old ones have been burnt away, since it does not matter which way they are loaded into the pistol.