| 摘要 |
A welded joint for metal pipes is provided with an inner lining, which is resistant to damage caused by the fluids flowing through them. The pipes are machined in the inside at the areas next to the ends to be joined, forming an undercut at each end. A spacer ring is inserted in the hollow annular space formed by both undercuts. The outer diameter of the spacer ring is substantially equal to the diameter of the corresponding undercuts, and its axial length is substantially equal or less than the sum of the axial lengths of the undercuts of the pipes to be joined. The spacer ring is made of an outer annular layer of a high thermal conductivity metal and at least one inner annular layer of heat-insulating and heat resistant material. The outer annular layer abuts in heat conducting contact with the metal pipes within said undercuts, and the metal pipes are joined by a weld seam.
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