Shaft alignment
Shaft alignment is the proper positioning of the shaft centerlines of the driver and driven components (i.e., pumps, gearboxes, etc.) that make up the machine drive train. Alignment is accomplished through either shimming or moving a machine component or both. Its objective is to obtain a common axis of rotation at operating equilibrium for two coupled shafts or a train of coupled shafts. Shafts must be aligned as perfectly as possible to maximize equipment reliability and life, particularly for high-speed equipment. Alignment is important for directly coupled shafts as well as coupled shafts of machines that are separated by distance—even those using flexible couplings. It is important because mis- alignment can introduce a high level of vibration, cause bearings to run hot, and result in the need for frequent repairs. Proper alignment reduces power consump- tion and noise level and helps to achieve the design life of bearings, seals, and couplings. Alignment procedures are based on the assumption that one machine-train component is stationary, level, and properly supported by its base plate and foundation. Both angular and offset alignment must be performed in the vertical and horizontal planes, which is accomplished by raising or lowering the other machine components and/or moving them horizontally to align with the rota- tional centerline of the stationary shaft. [unique_solution]The movable components are designated as machines to be moved (MTBM) or machines to be shimmed (MTBS). MTBM generally refers to corrections in the horizontal plane, while MTBS generally refers to corrections in the vertical plane. Keith Mobley /Maintenance Fundamentals Final Proof 15.6.2004 4:57pm page 71 71 Too often, alignment operations are performed randomly, and adjustments are made by trial and error, resulting in a time-consuming procedure. Because of this problem, Integrated Systems, Inc. (ISI) developed this module to help mainten- ance technicians speed up the alignment process. It presents a step-by-step procedure for the proper alignment of machinery and discusses shaft alignment fundamentals, equipment, measurements, and computations. Because there are certain basic math skills needed to perform alignment computations, a math review also is included.