| 摘要 |
<p>A collar for controlling thermal and mechanical stresses and for reducing failures caused by such stresses in gas-transfer tubings, or pigtails, used in a steam reformer. The control collar, in the form of a section of tubing and having the same alloy composition as the pigtail, is placed over each end portion of the pigtail connected to an extension member attached respectively to a catalyst tube in the steam reformer and to a gas-removal manifold. The control collar fits closely over the pigtail and is welded to the extension member. Use of the same alloy composition in the pigtail and in the control collar eliminates stresses associated with differences in thermal expansion and contraction, and the use of the collar reduces mechanical stress fatigue by displacing the point of maximum bending movement from the area of mechanical stress concentration of the weld, and the metallurgical notch in the heat-affected zone of the weld.</p> |
