Help: Problem with compressor alignment
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The unit I have here is a centrifuge driven by an electric motor, with a gearbox in between. Alignment is done by using the gearbox as a reference point to locate the compressor and the motor. I’m facing a problem right now: using the three-instrument alignment method, with two instruments for axial alignment and one instrument for radial alignment. The figure below shows the data from the radial instrument used to align the compressor; the values 16.8 do not equal 0.38. The instrument holder is mounted on the high-speed shaft of the gearbox, and it’s possible to feel a gap between the bearing and the shaft when using manual adjustment. Does anyone have any advice?
Oh, sliding bearings do have this kind of error; the same position during forward and reverse rotation shows different behaviors. My approach is to combine the data as comprehensively as possible to achieve the best result.
The last edit to this post was made by we11we11 on 2019-10-28 at 12:52. It’s best not to rotate the gearbox while it’s aligned. As you mentioned, it’s possible to feel a gap between the bearing of the high-speed shaft and the shaft itself by hand; this likely occurs during rotation as the gears may push the high-speed shaft away from its bearing, resulting in inaccurate readings. For gearboxes of this type, try rotating only the compressor and the motor separately to see if the readings are accurate
It’s best to take photos when you align it, so that it’s easier to identify what the problem is; otherwise, it’s just guessing based on text alone. There’s also the issue of aligning the machine components – and yet the focus is on the gearbox, while the motor and compressor are ignored? If the compressor is higher or lower than the gearbox, then shims need to be used for the compressor; in that case, can it move freely left, right, up, and down? When aligning, prioritize the component that is difficult to move and has high precision requirements; choose those with lower precision needs and are easier to move. For compressors, we start by focusing on the gearbox, and then determine the location of the motor based on the gearbox. Both gearboxes and motors usually come equipped with set screws. If there is a height difference, simply use a crane or winch to apply some force. How do you manage to locate the compressor using the gearbox as a reference point? Is the industry pulling back on compressors? Use a crowbar to pry open the compressor? In the case of a reciprocating type, won’t the packing and piston rings break? With centrifugal types, the dry gas seal doesn’t get damaged; P
I agree quite a bit with the view from the 4th floor on this issue. We have encountered this issue before as well; there is indeed a significant gap when it comes to synchronizing the turning of the disks. Later, considering the clearance issue with the speed increase gearbox, single-sided turning of the machine was adopted; by using the speed increase gearbox as a reference point to locate the compressor and motor, the problem was resolved, and the equipment operated very stably! Oh, by the way, our compressor unit is a centrifugal unit from Shaanxi Gas Turbine; I hope this is helpful to you!
Yes, gearboxes are generally not rotated manually. As for what was mentioned above – whether to look for the gearbox on both sides or to look for it near the compressor and motor – there’s no problem with that; it mainly depends on the manufacturer’s requirements
Our gearbox won’t move; it’s a speed increase gearbox with pins that are inserted at an angle, and it can’t move up, down, left, or right
With the gearbox as the reference, doesn’t the high-speed shaft stay stationary? Just rotate the compressor?