| 主权项 |
1. A joined pyrolysis-furnace tube comprising:
(A) a first pyrolysis-furnace tube, the first pyrolysis furnace tube having (i) an outer surface, (ii) an inner surface, (iii) first and second faces, and (iv) the inner surface having N fins each fin comprising a fin tip adjacent to two fin roots, wherein (a) the outer surface and the fin roots are separated by an average distance t1, (b) each fin tip protrudes inward an average distance t2 from the fin root, (c) the first pyrolysis furnace tube comprises ≧17 wt. % chromium, and ≧15 wt. % nickel, based on the weight of the first pyrolysis furnace tube, and (d) N≧6; (B) a second pyrolysis-furnace tube, the second pyrolysis furnace tube having (i) an outer surface, (ii) an inner surface, (iii) first and second faces, and (iv) the inner surface having N′ fins each fin comprising a fin tip adjacent to two fin roots, wherein (a) the outer surface and the fin roots are separated by an average distance t1′, (b) each fin tip protrudes inward an average distance t2′ from the fin root, (c) the second pyrolysis furnace tube comprises ≧17 wt. % chromium, and ≧15 wt. % nickel, based on the weight of the second pyrolysis furnace tube, and (d) N′≧6; and (C) a tube joint, the tube joint connecting the first and second pyrolysis furnace tubes and being open to the flow of fluid, wherein
(i) the second face of the first pyrolysis furnace tube is joined to the first face of the second pyrolysis-furnace tube, the second face of the first pyrolysis-furnace tube having substantially the same exterior cross-section as the second pyrolysis-furnace tube,(ii) the second face of the first pyrolysis tube has (a) a first counterbore extending away from the second face to a first location a distance L/2 into the first furnace tube, the first counterbore being a substantially cylindrical counterbore with L being in the range of from (t2/t1)·2.5 cm to (t2/t1)·12.7 cm, and (b) a second counterbore, the second counterbore being a substantially conical counterbore beginning at the first location and extending outward at a conical angle in the range of from 5.0° to 20.0°, and(iii) the first face of the second pyrolysis tube has (a) a first counterbore, the first counterbore being a substantially cylindrical counterbore extending away from the first face to a second location a distance L′/2 into the second furnace tube, with L′ being in the range of from (t2′/t1′)·2.5 cm to (t2′/t1′)·12.7 cm, and (b) a second counterbore, the second counterbore being a substantially conical counterbore beginning at the second location with the conical angle being in the range of from 5.0° to 20.0°. |
