Generic selectors
Exact matches only
Search in title
Search in content
Post Type Selectors

Why Do I Need to Align the Coupling in the First Place?

Industry Topics

Why Do I Need to Align the Coupling in the First Place?

Why do we need to align a coupling in the first place?  If you ask the mechanic, maintenance manager, reliability technician, or plant engineer, you might get four different answers!  But these are probably common:

  • Increased reliability of the equipment being aligned.
  • Decreased wear on bearings, seals, gears, couplings, shafts, and other components that make up the machines being aligned.
  • Reduced vibration levels.
  • Decreased energy consumption (typically a small amount, but sufficient misalignment can cause increased energy consumption).
  • For warranty purposes, because OEM’s or owners specify it.

We can all agree on these.  Now, let’s step it up a bit.  How closely do we align?  Ask the same group, and you will probably get differing answers again.

So, let’s take a common coupling – a T.B. Woods 8JE – and see what we find.  This coupling is on a standard overhung water pump, axial suction, vertical discharge, operating at 1785 rpm.

Chart of maximum rpm allowable misalignment

 

Courtesy of T. B. Woods Inc.

 

 

    • According to T. B. Woods, this coupling can tolerate a MAXIMUM misalignment of 0.020” offset (rim reading), and 0.094” of angularity (face reading).  Woods is not being deceptive in their statement.  It is a maximum value, not an alignment tolerance.
    • According to the plant engineering department, the company alignment tolerance is 0.005” Rim and face (angularity and offset).
    • According to VibrAlign, the recommended shaft alignment tolerance is 0.0007” per inch of angularity, and 0.004” offset.  (The other laser alignment tool manufacturers are relatively close to the same tolerance.)
    • Ask the millwright and they may say, “I get mine to +/- 0.002” (we are a proud bunch!).
If I selected the tightestalignment tolerances from these different sources, and made it my alignment target, could I achieve it in a reasonable amount of time?  Alignment
  • With laser alignment tools?  Yes, and they do the math for you!
  • With dial indicators?  Probably so, if you’re good, and know how.  But it will almost surely take longer.
  • With a straight edge and feeler gauges or calipers?  You might, but it’s going to take many hours, several repetitions, and a great deal of added effort.

If you can achieve a great alignment in a reasonable amount of time, why not do it?  To my knowledge, you really can’t align shafts too closely.  In our training classes and our service work, we routinely align shafts to within 1 mil offset, and .3 mils angularity per inch-usually within 30 minutes, and one spin of the shafts.

So, if you can achieve a really close tolerance in a minimal amount of time, why not do it right, do it once, and forget about it!

For more information, email Stan at stan.riddle@vibralign.com or visit www.vibralign.com

Related Articles

Related Whitepapers

8-Steps to Successfully Implement a Preventive Maintenance Program

This is an overview of the implementation steps in a typical Preventive Maintenance (PM) improvement project. Most of the processes can be applied to a…

Axial Flow Check Valves for Pumps and Compressors

Pumps and compressors are essential devices used in a wide range of industrial plants and buildings. They are the power source that make it possible…

Proven Seal Technologies for CO2 Capture and Supercritical Applications

Advanced seal technologies for CCUS and sCO2 applications support energy transition initiatives Companies increasingly are prioritizing energy transition initiatives to reduce greenhouse gas emissions known…

Accurate & Reliable Pumps for Lease Automatic Custody Transfer (LACT) Units

Hydra-Cell Seal-less Pumps provide accurate and reliable custody transfer of crude oil, produced water, and NGL’s. They feature a compact design, require minimal maintenance, and…

Comments

Leave a Reply

Your email address will not be published.

Join the #PumpTalk Community


By submitting this form, you are consenting to receive marketing emails from: Empowering Pumps & Equipment, 2205-C 7th Street, Tuscaloosa, AL, 35401, http://www.empoweringpumps.com. You can revoke your consent to receive emails at any time by using the SafeUnsubscribe® link, found at the bottom of every email. Emails are serviced by Constant Contact