Theo dõi và phân tích rung động là phổ biến nhất của các công nghệ bảo dưỡng dự. Nó cũng được sử dụng đúng mức của những công cụ này. Chương trình bảo trì tiên đoán dựa trên rung nhất sử dụng ít hơn 1% của sức mạnh công nghệ này cung cấp. Các thiếu sót cơ bản của truyền thống bảo trì tiên đoán là | 314 An Introduction to Predictive Maintenance Figure 14-25 Load from narrow strip concentrated in center. Figure 14-26 Roll loading. This extremely important factor can be used to evaluate many of the failure modes of continuous process lines. For example the vibration profile resulting from the transmission of strip tension to the roll and its bearings can be used to determine proper roll alignment strip tracking and proper strip tension. Alignment Process rolls must be properly aligned. The perception that they can be misaligned without causing poor quality reduced capacity and premature roll failure is incorrect. In the case of single rolls . bridle and furnace rolls they must be perpendicular to the pass line and have the same elevation on both the operator and drive sides. Roll pairs such as scrubber backup rolls must be parallel to each other. Failure-Mode Analysis 315 SIGNATURE AT LEFT BEARING SIGNATURE AT RIGHT BEARING Figure 14-27 Typical vibration profile with uneven loading. Figure 14-28 Vertically misaligned roll. Single Rolls. With the exception of steering rolls all single rolls in a continuous-process line must be perpendicular to the pass line and have the same elevation on both the operator and drive sides. Any horizontal or vertical misalignment influences the tracking of the strip and the vibration profile of the roll. Figure 14-28 illustrates a roll that does not have the same elevation on both sides . vertical misalignment . With this type of misalignment the strip has greater tension on the side of the roll with the higher elevation which forces it to move toward the lower end. In effect the roll becomes a steering roll forcing the strip to one side of the centerline. The vibration profile of a vertically misaligned roll is not uniform. Because the strip tension is greater on the high side of the roll the vibration profile on the high-side bearing has lower broadband energy. This is the result of damping caused by the strip tension. .
