Blog

March 30, 2012

A Leg to Stand On?

By Stan Riddle

poorly-installed-base-for-shaft-alignment

A VibrAlign trainer recently conducted a shaft alignment training class on the Fixturlaser XA Pro. This 1 ½ day class includes one day of classroom training, followed by a half day of field training, usually on the customer’s own in-plant machinery, using their new shaft alignment tool.

While conducting the classroom portion of the training, one of the maintenance managers commented, “We’ve got a pump we’d like for you to help us align. It was recently installed, but it hasn’t been aligned.”

The machine is a 75hp motor, driving a centrifugal pump. A brief inspection of the pump revealed one other problem – one that could shorten the life of the machine as much as misalignment.

Do you see it? How could this affect the effectiveness of the alignment? What would you do different?

6 Comments

  1. Michael Keohane on April 20, 2012 at 6:04 pm

    Stan,

    Are all corners of the base mounted on threaded rod like that? If so I would anticipate having other problems such as resonance show up. Also it would seem like it would be almost impossible to have a flat mounting system with everything tight.



  2. Stan Riddle on April 20, 2012 at 9:24 pm

    Yes, all corners are like that. They used heavy gauge steel for the structure, but the threaded rod is not sufficient to support the weight of the machine, piping, and the dynamic forces from operation. You are correct about both resonance issues, and the difficulty of alignment. Good eye!



  3. Jack McLemore on May 21, 2012 at 2:40 pm

    For my info why would they ever mount anything like that?



  4. Stan Riddle on May 21, 2012 at 4:49 pm

    Great question Jack! I wish I had an equally good answer. I can only assume either no one knew better, they hoped the base would last longer, since it wouldn’t be touching the floor, or it was just easier to hook to existing piping. It’s not the first one I’ve seen, and sadly, may not be the last.



  5. Mike Franzen on July 17, 2012 at 11:53 am

    Stan,

    It looks like to me they tried to make it fit the piping instead of installing and plumbing to it. This is a unstable base with lot of vibration issues. Even if you get it aligned it will never hold one. It should have been mounted on floor and solidly mounted and had a base poured around it. I believe three times more mass than the pump and motor so it could dampen the vibration.

    Mike



  6. Stan Riddle on July 17, 2012 at 12:21 pm

    Mike, you are exactly right, I believe. They ran the pump to the pipe, istead of running the pipe to the pump. I learned the 3:1 rule of thumb too, but you don’t see as much of it anymore. For many machines, it’s more like 1:3. A base of threaded rod like this one will twist like Chubby Checker!