In the 35+ years of experience that LUDECA has in shaft alignment, we have been asked this question many times. How long does it take to do an alignment? People in charge of scheduling have a tough task when allotting time for technicians to do an alignment with precision. In many cases, they may just take a guess, based on the average time it has taken in the past. The answer is not so simple. During a one-day seminar, I had to perform an alignment on a motor to a pump to show the proper steps when aligning a machine. When the time came to start the alignment, all the safety procedures had been taken care of, and the machine had been rough aligned. The soft foot values were within tolerances. So I was able to align the machine in under 45 minutes, within the tolerances specified for 1200 RPM.
On another occasion, I was hired to help align a generator to a turbine. Quite a few things went right as well. The safety procedures had been taken care of by the time I got there. The coupling guard and coupling element had been removed. The machine had also been rough aligned. The special-order shims for the generator feet were available on-site. Even with all these things going my way, this alignment took a day and a half to finish. There are things that come up during an alignment that cannot be planned for. One of them is a soft foot condition. Not checking for soft foot can greatly increase the time it takes to align a machine, mainly because the response to corrections stipulated by your alignment tool will not be accurate. Therefore, knowing the soft foot condition and minimizing it, is key. However, that in itself can take up a long time, depending on the condition of the baseplate, the condition of the anchor bolts, washer, pipe stress, etc.
In both cases, they were a single coupling alignment. Aligning a large generator is obviously more difficult than a 200HP motor. In the first case, I was able to turn the motor with a strap wrench by myself. In the case of the generator, it needed to be uncoupled because the two machines could not be turned together. In most cases, a larger machine takes longer to align because breaking the bolts loose, alone, could take 20 to 30 minutes. Furthermore, there can be a large difference in the amount of time it takes to finish an alignment, between two identical machine sets. The information obtained here can help reduce the alignment time.
I recommend downloading our 5-Step Shaft Alignment Procedure and/or requesting our Shaft Alignment Fundamentals Wallchart for your alignment team. The point is that there is no fixed amount of time required for an alignment of a machine. If a scheduler should err, it should always be on the conservative side.
Alignment, Maintenance Tips by Adam Stredel CRL