Maintenance technology for tilting-pad radial bearings in turbine compressors

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I. Disassembly procedure for radial bearings 1) Remove the sensor probes and other instrument connections that hinder the disassembly of the bearings. 2) Remove the bolts and positioning pins on the split surface of the bearing cover, then gently lift the bearing cover using a jacking screw. 3) Remove the bolts on the split surface of the bearing housing, and take off the upper part of the radial bearing. 4) Gently lift the shaft using specialized tools for lifting shafts; the lift height should be such that the lower half of the bearing can rotate around the shaft, with the elevation not exceeding 0.15 mm. Flip the lower bearing housing around the shaft to the upper part of the journal, and remove the lower bearing. Note: The rotor must not be lifted from both ends simultaneously, nor should a crane be used to lift the rotor without removing the large cover first. The bearing bush with a thermistor must not damage the instrument wires during flipping. 5) Record the position and orientation of each bearing shell, loosen and remove the positioning screws on the back of the shells, and then take out each shell one by one. II. Technical requirements for the maintenance of radial bearings 1) Tilting bearing shells ① The Babbitt metal of the bearing shells shall be free from defects such as cracks, chipping, delamination, burning, crushing, wear, and roughness. The surface of babbitt alloy must be free from axial scratches and grooves, and the depth of circumferential scratches and grooves shall not exceed 0.10 mm. The tiles are inspected by coloring or dipping in kerosene; the babbitt should fit well, with no uneven wear on the surface, and the contact marks should be uniform along the axial direction. ②The load-bearing surface on the back of the tile is smooth; the contact marks with the tile shell are uniform along the axial direction and maintain line contact. For tiles that swing around a pivot, the load-bearing surface makes even contact, and there is no looseness or wobbling in its fit with the pivot pin. The back of the tile shows no signs of burning or wear caused by heavy loads. ③The edge where the tile meets the oil has a smooth transition, which is suitable for oil flow to enter the oil wedge. ④The thickness of tiles in the same group should be uniform; the difference in thickness between them should be measured using a dummy shaft or journal, and must not exceed 0.01 mm. ⑤The pin holes on the back of the tiles and the corresponding pins should show no wear or uneven wear; the diameter clearance of the positioning pin within the pin hole should be at least 2.0 mm. After assembly, the clearance between the pin and the top of the pin hole should be at least 1.5 mm. The tiles move freely inside the tile casing without pressing against each other. ⑥Tile with a thermosensitive element, in which the thermosensitive element is firmly fixed to the tile without any looseness, and the lead wires have good insulating protection. After assembly, the thermosensitive element and leads do not prevent the tiles from moving freely within the tile housing, nor do they affect the overall assembly of the bearing. ⑦The back contact wire passes through the geometric center of the back side of the tile; the shapes on both sides of the contact wire are symmetrical. When swinging around the contact wire, no part of the tile surface should be lower than the oil seals on either side (when the rotor is installed). ⑧When axial pressure is applied to the lower bearing pad, the two pads on the left side should bear the load evenly. 2) Bearing shell: ① The mid-surface of the bearing shell fits tightly, and the positioning pins are in good fit; after tightening the bolts on the mid-surface, there is no gap in that area. ②The oil seals on both sides of the bearing shell show no wear, and the clearance is within acceptable limits. The oil seal seals tightly by joining at the top, bottom, and middle, without pressing against the bearing housing; the floating type of oil seal moves flexibly, with no cracks on its end face. ③Use red lead to check the contact condition of the tile shell within the lower bearing housing; it should be in good contact. The left and right sides are level with the mid-plane of the bearing housing; the gaps on both sides are uniform in all directions, being no more than 0.05 mm. The anti-rotation pin of the shell does not protrude above the mid-plane of the bearing housing. After tightening the mid-plane bolts, the mid-plane of the tile shell and the mid-plane of the bearing seat fit together tightly with no gaps. ④The tension or clearance on the back of the bearing shell meets the manufacturer’s design requirements. ⑤The oil inlet and outlet holes of the shell are aligned with the corresponding oil holes in the bearing housings, and the vibration probe holes, temperature measurement holes, etc., can also be aligned. The flow-limiting screw of the oil inlet hole in the tile shell is not loose and is securely fixed, with a pore diameter that meets the design requirements. The oil inlet and outlet holes are not blocked.