GB1486728A - Heat exchangers - Google Patents

Abstract

1486728 Blasting; laminar forging; making heat exchangers KRAFTWERK UNION AG MANNESMANNROHREN-WERKE AG and SANDVIK AB 24 March 1975 [1 April 1974] 12267/75 Heading B3D B3H and B3A A process for imparting compressive stress to a zone of a wall of a heat exchange tube 15, which zone is bounded by a surface of the wall, comprises subjecting the tube to surface coldworking, such as by blasting or hammer forging. In apparatus for carrying out the process by blasting, the tube 15, which is U-shaped is placed on a feed conveyer 2, Fig. 2, having horizontal rollers 21 driven by a motor 23, and vertical rollers 22 adjustable to the spacing of the limbs of the tube. A turntable 42 is rotatable through 180 degrees by a drive 43, 44 and carries a blasting compartment 45 containing a nozzle head 41. A second conveyer 3 is disposed on the other side of the turntable. In use, the conveyers are driven so that one limb of the tube is treated in the blasting compartment until a photo-electric cell stops the motor 23 and simultaneously actuates the drive 43, 44 and the turntable is driven through 180 degrees for treatment of the curved portion of the tube. When the curved portion has been treated, the drive 43, 44 is stopped and the conveyers driven in the reverse direction so that the other limb of the tube is treated. The turntable 42 is supported for rotation on ball bearings 50, Fig. 3, and has a blasting head 41 consisting of an annular array of nozzles 41a supplied with abrasive particles, such as glass beads of 0À1 to 1À5 mm. diameter, through a line 47. Spent abrasive falls through apertures 42a into a container 46 leading to a cyclone separator 80, the useful particles and particles from a hopper 82 controlled by a valve 84 being projected along the line 47 by a nozzle 48 connected to a compressor 49. In another embodiment, two tubes 15 are connected by plugs 17, Figs. 5 and 6, to form a closed loop and placed on supports 61 which are hinged to move downwardly as a blasting device 5 guided by a wheel 57 engaging the tube moves around the loop, the device being supported by rollers 54, 55 on an outer rail 6 and the loop. In a similar embodiment, the blasting device is replaced by a hammer forging machine, Fig. 8, carried by a carriage 76 supported by rollers 77 on the outer rail 6. A frame 73 has rollers 72 supporting a head 71 which is rotated by a friction roller 74 driven by a motor 75 and has a number of forging units 78 operating on the resonance principle. Reference has been directed by the Comptroller to Specification 1,408,379.