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Three Simple Tricks To Improve Alignment

Given that shaft misalignment is responsible for up to 50 percent of all costs related to rotating machinery breakdowns, surely you’d want to make sure it’s done properly?

Sometimes, the simplest things make the biggest difference.

That’s certainly true with regards to alignment and if you take care of three simple elements, you can make just about every alignment job easier, faster and more effective.

The three things are:

  • Minimising soft foot
  • Controlling the looseness of the coupling
  • Tightening the feet of the machine

Regardless of the type of measuring equipment you’re using, from laser alignment tools, dial indicators and straight-edges to feeler gauges or any other device, these three things will improve the accuracy and repeatability of your measurements.

Minimising soft foot.   The term ‘soft foot’ is the common term used for less than perfect contact between a machine’s feet or casing and the surface of the supporting base plate or frame.

It’s one of the most prevalent conditions found in rotating machinery and if it’s not corrected, the alignment job will be far more difficult and sometimes even impossible.

When there’s distortion as a result of the mounting feet not being coplanar, individual feet being bent or angled or if the mounting surface isn’t flat, mechanical and electrical problems are likely to arise and the repeatability of the alignment values will be compromised. Soft foot will cause a machine to shift position during the tightening process, and this movement can either be vertical, horizontal or more commonly, a combination of the two – resulting in non-repeatability of alignment values.

If you fail to minimise soft foot, the alignment process will be more complicated than it should be and will take far longer than it ought to.

Controlling backlash. 

Coupling backlash isn’t as problematic as soft foot, but it’s not far behind.  Monitoring it and keeping it to a minimum is essential for accurate alignment.

Simply put, backlash or ‘coupling looseness’ is angular movement in any mechanical system between mating parts, and although some types of flexible couplings are designed to have a slight degree of looseness, if it’s not controlled, it can result in erratic shaft alignment values.  This can happen when measuring with both lasers and indicators because any changes in the relative angular positions of the shafts will affect the accuracy and repeatability of the readings.

You need to make sure that there’s no excessive backlash, so always inspect the coupling inserts for signs of excessive wear.    Replace worn or defective inserts before doing any measurements and rotate the shafts in a consistent direction to maintain torque.  If need be, temporarily override the opportunity for the coupling to backlash by using duct tape or other mechanical means.

Tightening the machine’s feet

Many factors affect the position of the machine during the tightening process including dirt or debris underfoot, pipe or conduit strain and the fact that it’s virtually impossible to get soft foot down to zero.   Always do a visual inspection of the machine, especially near the components that are to be aligned to check for signs of pipe strain.

It is critical to minimise the likelihood of the machine moving, and one of the ways of doing this is to loosen or tighten the feet in a diagonal or criss-cross pattern.  Remember, this should be done every single time you adjust the machine.

These three things will significantly increase the accuracy and repeatability of your measurements, helping to correctly align your machinery to prevent breakdowns and reduce unplanned downtime and lost production.

For practical and cost-effective answers to any alignment challenge, talk to the industry leaders, Nexxis.  We carry an extensive range of advanced laser alignment tools and other measurement devices to keep your operation running at peak performance.  Contact us to discuss a tailor-made inspection or non-destructive testing solution for your unique needs or browse our website to see our extensive range of quality products.

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