GB896629A - Improvements in or relating to methods and apparatus for coating tube interiors - Google Patents

Abstract

896,629. Coating with metals; alloys. BUNDY TUBING CO. Dec. 30, 1959 [Dec. 31, 1958], No. 44221/59. Classes 82(1) and 82(2). The interior of a tube is coated with an alloy that has plastic properties in a range of temperatures between its melting and freezing points by introducing molten alloy into the tube interior, distributing said alloy over the interior surface of the tube before the alloy has cooled to below said range of temperatures, and then cooling said alloy so as to solidify it. In operation of the apparatus shown, tube T is introduced through guide 30 between rolls 20-23 which spin the tube about its longitudinal axis and advance it to the left. Magnetic proximity switch 41 is actuated when the tube approaches it and stops the drive for the rolls, releases timer 42 and energizes relays 45, 46 for closing switches 43, 44. The tube remains at rest for a period determined by timer 42 and during this period the portion of the tube between rolls 26, 27 and 13, 14 is heated by passage of current from transformer 32. When timer 42 times out, rolls 20-29 are actuated for moving the tube to the right. Simultaneously, valve 7 is opened so as to spray molten alloy on to the interior of the tube from nozzles 9, this alloy being derived through pipes 6, 8 from vessel 1 by operation of pump 4. Enlargement 12 on pipe 8 smoothes the coating while it is still plastic, and coolant 36 emitted from pipe 37 then rapidly solidifies the coating. Proximity switch 39 stops operation of the apparatus. Suitable coating alloys are Sn 99%, A1 1%; Sn 90-99%, Cd 1-10%; Sn 95%, Sb 5%; and Zn 95%, Sn 5%.