tube de fumée

CONT: Steel boilers are fabricated into one assembly of a given size and rating, usually by welding. The heat exchange surface past the firebox usually is an assembly of vertical, horizontal, or slanted tubes. The tubes may be firetube (flue gas inside, heated fluid outside) or watertube (fluid inside).
CONT: The firing tubes are copper clad on the water side. The 2 in. OD by number 13 gauge tubes are formed by telescoping a .030 in. hard phosphorized copper tube over a .065 in. seamless steel tube and drawing over a mandrel and through a die for a tight bond. Long tube life is positively assured under the most aggressive conditions.