Most every week during one of our alignment training classes, we’ll get a question about aligning cooling towers. Most facilities we visit have them and a lot of folks aren’t too sure how to approach the job. We’ll tackle the first step in this episode and explain a bit about roughing in the motor to the gearbox.
As with all successful alignments, planning the job beforehand can save a lot of headaches–especially when it comes to cooling towers. The long span of the spacer shaft, the physical separation of the motor and gearbox, limited access or tip-toeing on concrete beams present a challenge. Here are a few pointers to get you started:
Rough-In – Roughing-in should be done to minimize the possibility of base-bound or bolt-bound conditions, and should be done while the fan is in construction or commissioning stages, or after a gearbox or motor replacement. The roughing-in process for a cooling tower fan with a spacer shaft is different than a standard motor-pump configuration since there may be several feet between the motor and the gearbox–and a 15 foot long straightedge just won’t work!
It is also very common for a cooling tower drive to be bolt-bound, base-bound, or both. Don’t be afraid to move or shim the gearbox to eliminate a bolt-bound or base-bound condition. If you must move the gearbox horizontally to correct a bolt-bound situation on the motor be mindful of blade tip clearance around the plenum. Also, if you experience a base-bound condition, where the motor is sitting too high, you can shim the gearbox slightly just under the inboard end of the gearbox.
A cooling tower fan using a spacer shaft can be roughed in with a laser alignment tool, using the following process:
If your lasers have sufficient target size to measure at least 90° of rotation, skip all of this, and let the laser do the roughing in and the alignment in one step!
Once the roughing in process is completed, or if you have sufficient range to take an initial measurement, continue with your alignment as you normally do.
There will be more on cooling tower alignments (which can be applied to all spacer shaft alignments) but if you have a question in the meantime, leave us a comment.