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Handbook Of Shaft Alignment Episode 3 Part 6

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Tham khảo tài liệu 'handbook of shaft alignment episode 3 part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 720 Shaft Alignment Handbook Third Edition FIGURE 21.75 Alignment models of the rotor in the north to south and west to east positions. 21.1.11.1 Additional Information on Gearboxes and Fluid Drives Moderate to excessive off-line soft foot conditions have been experienced on virtually every gearbox regardless of frame construction design. Gearboxes are frequently bolted to the frame in more than four points and soft foot correction can be more difficult to correct the Alignment Considerations for Specific Types of Machinery 721 FIGURE 21.76 Gearbox. machines bolted in three of four points. Uncorrected soft foot can distort the housing causing meshing problems as shown in Figure 21.80 through Figure 21.82. Since there is typically a rise in casing temperature from OL2R conditions not only will the shafts move upward but they will also spread apart. Several OL2R studies have shown that gearboxes and fluid drives can twist or warp when operating. If dowel pins are used casing distortion can occur if all four corners are pinned to the frame. FIGURE 21.77 Steam turbine gearbox and fan drive system. 722 Shaft Alignment Handbook Third Edition FIGURE 21.78 Motor gearbox compressor drive arrangement. One method to compensate for the lateral expansion of a gearbox is to pin the high-speed shaft and allow the low-speed shaft to move into alignment during normal operation as shown in Figure 21.84. The one dowel pin at the high-speed shaft acts as the control point for the gearbox. The dowel pin at the opposite end of the high-speed shaft allows expansion in the axial direction but prevents the gear case from translating laterally. The bolts nearest to the dowel pins should be 90 -100 of final torque value. The torque on the foot bolts should be less as the distance from pins increases. This lower torque setting will hopefully allow the case to slide between the underside of the bolt head and the gear case foot yet still provide a hold-down force to the baseplate or soleplates.