May 13, 2020
Don’t Be Tempted!
By John Pasko
Often the OJT portion of our training classes begins with an alignment check of a rotating piece of machinery in the client’s facility. This comes after numerous alignments in the classroom, on the training fixtures, performed by the attendees.
They are then ready to apply their skills learned on the classroom training equipment in their plant. A typical scenario for the OJT training is that the “alignment check” becomes a full-blown precision shaft alignment. When this happens, the class find themselves at a crossroads.
Do we stop, break the coupling apart, rough-in, check for obvious and final soft foot (perform the 4 pre-alignment steps) or do we proceed from where we are at? The laser sensors are in place, the coupling is coupled, and the equipment has already been operating in this condition.
A number of my classes have chosen to start from the latter spot, bypassing proper rough in, soft foot and the other pre-alignment checks. They choose to use the operating condition as a starting point because after all “we are really close to begin with”. I typically step back and watch them struggle with the alignment. Why do they struggle? Because the coupling strain has not been removed (rough in) and soft foot has not been corrected.
It usually takes a while before the group gets the permanent message emblazoned on their memory banks. The reason we train so hard on the 4 pre-alignment steps in the classroom is because years of industrial experience has taught us the value of the time spent on these 4 preliminary yet essential principles. No matter what.
This has happened so often that I now start off the OJT portion of class with the strong warning “you will be tempted” to skip straight to making corrections after the alignment check reveals misalignment.
A recent class found themselves in just this situation. Even after my advice to “not to be tempted”, they completed their alignment check, found misalignment and immediately began making corrections. After making their first shim change, with all of their hold down bolts still loose, they found one shim stack to be sloppy loose. They realized they had obvious soft foot and were reminded of my pleadings not to be tempted to skip the pre-alignment steps.
They stepped back, performed the 4 pre-alignment steps and completed the precision shaft alignment, using the Verti-Zontal Process, in two moves on a 3600 RPM, 800 horsepower, twenty-nine stage, centrifugal pump.
Afterwards they stated the lesson was learned and how important it is to not be tempted to take shortcuts during a precision shaft alignment and skip the pre-alignment steps.
For further information on the essential Pre-Alignment Steps check out these videos: