April 11, 2012
By Chris Troutt
Not too long ago I was called to one of our sister shops to perform a laser shaft alignment on a 3600 RPM skid-mounted end-suction ANSI pump. Easy, right? Honestly, I made a few mistakes right off the bat:
- Thinking this would be easy (and starting right before quitting time).
- Taking for granted that all surfaces had been properly cleaned and inspected.
- Not doing all the steps that I have been taught and the same steps I teach our techs.
- Not asking why it was in for repair.
I performed a quick pre-alignment, mounted the equipment and took a reading. The motor needed to come down over 200 mils and move horizontally 406 mils. I wasn’t expecting that. So we took another set of readings with the same results. A quick look at the coupling did not show it being off this much.
So I stepped back and thought…..”What am I missing?”
I wanted to ensure we did not have a laser issue, so we mounted the laser alignment equipment to a piece of stock in a lathe and took some readings. All repeated, three times in succession, so no laser issue! I inspected the shaft and coupling run outs, and did a thorough visual inspection of the entire unit. I pulled the pump off the base, cleaned rust from the base feet, scrapped off a coating on the base, and did the same to the motor. Next I removed both the couplings, looked for burs/dings on the fits, faces and bores. Ensured a slip fit on all coupling hubs, key-ways, and bores. Then I replaced all bolts with new hardened bolts and flat washers – no lock washers! I did soft foot checks on both motor and pump uncoupled from each other, and did find some in the pump. I tightened everything down using a three-pass method, did a final soft foot check, and started a fresh alignment.
This alignment check indicated the motor was 101 high in the front and 103 high in the back, and the horizontal was out 45 in the front and 98 in the back. I made all corrections in about 15 minutes, with one spin of the shaft. Final readings were well within a 3600 spec!
Lessons of the day…
- Always check for yourself. Your idea of “ready for alignment” may not be everyone else’s.
- Don’t overlook all the alignment steps, sometimes it takes a little more than a couple soft foot checks and a torquing sequence to get an alignment to go well.
- After seeing the old coupling, I knew why it was in for repair! It had worn off the original teeth and had cut new ones 3/8″ below where they should have been. This thing had serious trouble in its alignment!
- Here is the biggie! Don’t let it get you frustrated; back up, take a breath, and cover the basics we all know. Most of the problems we see can be eliminated through simple fixes.
I am not sure what part of my “basics” check list eliminated my trouble spot, but through all of that I got the bad actor out of it!
From VibrAlign – Special thanks to Chris Troutt, Reliability Analyst at BRI (a Cogent Company based in St. Louis, MO) for a great blog post! We want to encourage any of our readers to post comments, questions, case histories and ideas to the blog. We’d love to hear what you have to say!