Coaxial heating pipe with corrugated inner and outer pipe - has flat portions in inner pipe locatable by markings on outer pipe

摘要

The co-axial pipe assembly is intended for carrying a liq. or gaseous line fluid and may be used i a district heating system. It comprises a corrugated inner pipe (1) pref. with a welded longitudinal seam and a corrugated outer pipe (2) pref. longitudinally seam welded. The inner pipe has short un-corrugated portions (5) at regular intervals. The outer pipe has external markings (6,7) coinciding with these portions os that they can be easily located. The pipe (2) may be externally plastic coated (4) and have the markings in the plastic coating. The markings (7) may consist of uncorrugated portions in the outer pipe.