Problems with coupling alignment and disc pumps
Thread Content
During my time at the construction site these past two days, I noticed two problems: 1) The pump is too small, so it’s not possible to position the dial indicator properly and rotate it 360 degrees, as the space below is insufficient. For on-site installation, can one keep the watch holder fixed and rotate the other half of the coupling in order to take readings, rather than using left+right- to obtain downward readings? Is this feasible? 2. When starting the pump after connecting it, a squeaking sound can be heard. The manufacturer said that it was tested before leaving the factory, and that it might be the sound of the mechanical seal; once water is present, there will be no problem after starting the machine. Is this statement correct?
The data obtained by rotating the coupling on one side is inaccurate; it is necessary to rotate both sides simultaneously for accurate results. Use a laser aligner to calibrate your pump. For checking the outer diameter of the small pump, a steel tape measure can be used; for checking the flat surfaces, a feeler gauge will also suffice – high precision isn’t necessary. If there’s a sound, check if the oil seal is touching something
The German Plüfke laser alignment device can provide alignment data with just a 60-degree rotation. Chengdu Tianchengxiang Technology Co., Ltd
When rotating the pump after connecting it, a squeaking sound was heard; this should be considered abnormal. Since the pump is small, it is incorrect to claim responsibility by not being able to rotate the dial indicator 360 degrees while aligning the couplings; both the site workers and the manufacturer must take responsibility for their work. You should stick to your principles: the equipment provided for your use should meet your requirements.
Reply to 1# Jiangtai Ren: I can’t say whether this method of using a meter is correct, but the squeaking sound that occurs when turning it might indeed be coming from the sealed end surface. I’ve seen many technicians: as long as the coupling bolts are inserted easily, they connect it right away and test the pump, and it still runs perfectly. Of course, this all requires many years of experience; one needs to have a clear understanding of it.
The test drive is about to take place, but the squeaking at the seal area has not been resolved yet. The manufacturer still says that there will be no problem once a medium is present. But I’m worried; apart from the issue with the mechanical seal, what other possible causes need to be ruled out?
For small pumps, calibration is generally not a major issue even without using a gauge; from a technical standpoint, such calibration does not meet the standards. There is a squeaking sound at the seal area, which might be caused by friction between the rotating ring and the stationary ring. Loosening the rotating ring of the seal slightly should eliminate this sound. The manufacturer claims that there is no problem once the medium is in use; to be more precise, it’s okay after some running-in time has passed.
Should I fill the pump and then try to turn it by hand? If that doesn’t work, then they are right
Use a dial indicator for alignment; three values are obtained, and the fourth value can be calculated to determine its correctness. If there is noise when turning the shaft, it needs to be checked to see if the shaft seal is wearing out Is the compression level too high? Do not drive blindly.
The manufacturer arrived; first, the machine seal was loosened to separate the rotating and stationary rings. There was still a squeaking sound when manually turning it, so it was determined that this issue was not related to the machine seal. Open the bearing cover, check the oil seal and apply some lubricant there; loosen it a bit, then rotate the pump. OK
The laser alignment device mentioned on the third floor – I’ve seen them used for compressor alignment, but they are all imported, expensive, costing over 60,000 yuan. Are there any domestic ones?