When adjusting the pipes of a centrifugal compressor to be stress-free, can the positioning pins of the spring supports be removed?
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For a centrifugal compressor with inlet and outlet at the bottom, with piping already installed, loosen the connection flanges to conduct a stress-free inspection. At this point, do the set screws of the spring-supported hangers on the pipes need to be removed? Should the torque tightening be completed first, before removing the positioning pin? Do compressor manufacturers require that there be no stress, and that the pins can only be removed after proper torque tightening has been achieved? However, when one of the pins is removed, the compressor’s alignment value changes significantly. I would appreciate some guidance from experts.
When performing stress-free adjustment of the piping in a centrifugal compressor, the positioning pins of the spring supports usually need to be removed after torque-controlled tightening is completed. This is because the function of the positioning pin is to maintain the position of the spring hanger; removing the pin before applying a fixed torque may cause the position of the spring hanger to change, thereby affecting the stress-free state of the pipeline. Therefore, as required by the compressor manufacturer, the pin can be removed only after torque tightening is completed. When removing the pin, it is normal for there to be a significant change in the compressor’s alignment; as long as the pipes are not under stress during the operation, that’s fine. .
When you removed one of the pins, the torque tightening wasn’t completed yet, right?
In this case, it should first undergo a stress-free inspection; once it passes, torque tightening should be carried out, and finally the pins should be removed
The pin that was pulled out after stress adjustment was completed and the torque was set. During torque-controlled tightening and pin removal, monitoring is carried out using a gauge attached to the coupling at the shaft end.
However, it’s only after removing the pin that the pipe operates in its normal state. If it passes the inspection and adjustment, then if there is a significant deviation in the value at the shaft end after the pin is removed, wouldn’t that render the purpose of stress-free adjustment meaningless?
I think it should be like this: although the pin cannot be pulled out before setting the torque, it is necessary to adjust the spring hanger so that the protruding part of the hanger’s positioning feature does not come into contact with either of the upper and lower positioning blocks. At this point, even without removing the pin, the support bracket is already in normal operating condition. After the torque is applied for tightening, the pin can be easily removed by hand.
Is it because the pipeline undergoes significant displacement after the plug is removed that this leads to an excessive deviation in the compressor’s alignment?
Since our compressors are skid-mounted, the supports and brackets are already adjusted in place during installation. My understanding is that the piping is installed extending from the compressor’s inlet and outlet to both ends; normally, jacks and slings are used to fix the pipes in their proper positions for welding and bolt tightening. After these tasks are completed, the supports and brackets are adjusted to secure everything in place. If the supports and brackets are adjusted right from the start, it’s unlikely there will be any errors, and no further adjustments will be necessary. I hope other sea friends can also share their experiences with on-site installation
So the adjustment should be done as follows: first adjust the spring hanger (without removing the pins, ensuring there is a gap between the protrusion and the upper and lower positioning clips) – then adjust the parallelism/radial deviation/gap of the flange – tighten it using a set torque – finally remove the positioning clips by hand (do not use a crowbar).