3. Mục tiêu của sự liên kết trục ĐỨNG Trong một hydrounit trục thẳng đứng hoàn toàn phù hợp, tất cả các thành phần quay sẽ được hoàn hảo plumb và hoàn toàn tập trung trong các thành phần văn phòng phẩm tại bất kỳ vị trí luân phiên. Các lực đẩy mang giày sẽ được cấp, với mỗi giày như nhau nạp và Á hậu lực đẩy sẽ được hoàn toàn vuông góc với trục. Khi tay đòn xoay, hoàn hảo | Figure 9. Typical turbine guide bearing. Figure 10. Typical segmented shoe guide bearing. 8 The segmented shoe type bearings are adjustable to allow adjusting the bearing clearance and the position of the center of the bearing. The sleeve type journal hearing may be doweled in place or the bearing shell may be a tight fit in the upper or lower bridge. Both the sleeve type and the segmented shoe bearings used on generators are partially submerged in an oil bath and lubricate through the rotation of the shaft. 3. OBJECTIVES OF VERTICAL SHAFT ALIGNMENT In a perfectly aligned vertical shaft hydrounit all the rotating components would be perfectly plumb and perfectly centered in the stationary components at any rotational position. The thrust bearing shoes would be level with each shoe equally loaded and the thrust runner would be perfectly perpendicular to the shaft. As the shaft turns perfectly centered in the guide bearings the only loading on the guide bearings would be from mechanical and electrical imbalance. As alignment deviates loading on the guide bearings will increase and so will vibration levels. Any increase in vibration from misalignment will decrease the factor of safety for operation in severe circumstances such as rough zone operation. If a unit has a moderate vibration problem caused by misalignment the driving forces that occur with draft tube surging or mechanical imbalance may be enough to cause damage to the unit. Since a perfect alignment isn t possible we need guidelines or tolerances to let us know when we are close enough. Table 1 lists tolerances for use in aligning a vertical shaft hydrounit. These are general tolerances and some judgement must be used in specific cases. In most cases a unit can easily be aligned within these tolerances but in some special circumstances it may not be possible without major modifications. When a major modification is required such as moving the generator stator the possible consequences of not doing it should
