Dale Weaver Inc
MACHINE TECHNOLOGIES GROUP

Laser Shaft Alignment

Precision Alignment Will Increase Bearing Reliability

Slight increases in misalignment can have significant effects on bearing life. Small misalignments cause forces to be transmitted to bearings that can reduce the useful life by many times depending on the coupling.

BEARING LIFE INCREASE

DWI Machine Technologies Group can help you design and implement a precision alignment program. We offer CSI Laser Alignment and Mastertrend Computer Tracking. Let DWI Machine Technologies Group help you reap the benefits and increase your return on your investment in machinery. Please call today.

Misalignment is broadly accepted as one of the most common faults found in rotating equipment.

What can be accomplished by using precision alignment in a proactive reliability based maintenance program?

Implementing a precision alignment program in a facility has produced the following results:

• 8x increase in bearing life
• 7 percent reduction in maintenance costs
• 12 percent increase in machine availability
• Breakdown maintenance attributed to misalignment was reduced 50 percent

Let us help you develop a precision alignment program and increase the life of your equipment and increase your profits.

Your machines are talking to you about alignment!

Symptoms of misalignment include:

• Premature bearing, seal and coupling failure
• Excessive vibration
• High bearing temperatures
• Excessive oil leakage at seals
• Loose foundation bolts
• Excessive coupling temperatures and wear
• Shafts breaking at the inboard bearings

Even small misalignments between rotating shafts cause the shafts to flex. This flexing or elastic bending as they rotate exerts abnormal forces on the bearings, couplings, and the shafts themselves. These forces lead to premature falures. In addition, in electric motors, this flexing alters the gap between the stator and rotor affecting their performance.

Let us help you develop and monitor an alignment program for your rotating equipment.

Machine Technologies Group helping you maximize the profit from your investment in machinery

Shaft misalignments can be costly

Studies of the effect of small misalignments show that very small misalignments can have significant effects on the life of bearings in service.

It has been shown that for a 6205 bearing a misalignment of .005 inches reduces the expected life by 45%! Maximum misalignments given in catalogs from coupling manufacturers are the misalignments under which the couplings will give satisfactory life. However, this maximum misalignment can cause forces that are excessive for the bearings and other components. Typically, these tolerances are several times those recommended by bearing manufacturers. Therefore one should not use the coupling specifications. Rather, the manufacturer of the of the equipment or bearing should be consulted.

Field studies of various machines have demonstrated that a precision alignment program can extend average bearing life by 8x. The resulting reduction in repairs, downtime, and loss of production can be dramatic. The return on your investment in equipment can be increased.

A precision alignment program requires trained people who have the best alignment systems and a dedication to obtaining excellent results. DWI Machine Technologies Group is just these kind of people and tools. We can help you design and implement a precision alignment program as well as other reliability centered programs that can increase your profits. Call us today and let us show you how we can help.

The importance of correcting "Soft Foot"

The term "soft foot" is actually a misnomer. There is nothing "soft" about a "soft foot". Instead, soft foot means the machine frame distorts as the foot's bolt is tightened or loosened. The effects of machine frame distortion (soft foot) are numerous. The most damaging are discussed below.

In the example below, the coupling moves about 16 mils every time the foot bolt is loosened or tightened. The exact amount of movement depends upon the machine frame rigidity. Worse, exactly how much the coupling moves depends on bolt tightening sequence and torque values.

The animation shows a machine with a soft foot and loose base bolts. The machine has straight lines scribed in the end housing.

The line pattern shows the effect after the bolts are tightened.  The curved lines are called stress lines and represent the distortion pattern in the machine frame due to soft foot. In the center of the housing are the shaft bearings distorted with the same pattern.

Notice that not only does the alignment change between the machines, but also that the alignment changes between the internal bearings! Since very few machines are built with self aligning bearings, internal misalignment is serious. Perhaps the single largest increase in machine life associated with eliminating soft foot comes from having the machines bearings aligned with each other. Many of the failed bearings, broken shafts, and high vibration readings associated with misalignment are actually caused by the misalignment between the internal bearings of a single machine, due to soft foot

If the machine frame is distorted due to soft foot, the bearings move relative to each other. Once the play is taken up in the bearings, the only way the bearings and housing can continue distorting is to deflect the shaft. The shaft extracts a price for such deflection by imposing a pre load on the bearings. The effects of bearing pre load due to shaft deflection are bad enough. But examine the action of the shaft as it turns.

Notice that every 180 degrees the shaft is forced into a position that bends it to an exact opposite curve. This back and forth bending is usually slight, by less than 20 mils, but it is cyclic, stress reversing, and happens every time the shaft turns around. For an 1800 rpm machine, the shaft goes through 30 stress reversal cycles every second. This amounts to 2,592,000 back and forth cycles every 24 hours. After a period of time, the shaft metal fatigues and snaps.

DWI Machine Technologies Group can help you eliminate soft foot from your machinery. The result will be longer life and a better return on your investment. Call today.

More about Soft Foot

As we discussed earlier, soft foot is the condition in which the frame of a machine is distorted by the anchor bolts being tightened or loosened. This condition also distorts the bearings as shown below.

As confirmation of this bearing distortion, observe the number of failed bearings that have two load zones 180 degrees apart. It is impossible to obtain two load zones in most machine bearings except by pre loading or distorting the outer race.

The major cause of outer race distortion in properly installed bearings is soft foot. Numerous equipment failures previously blamed on shoddy bearings, operation upsets, operation procedures, poorly built equipment and so forth are actually due to soft foot.

DWI Machine Technologies Group alignment procedures remove the effect of soft foot prior to shaft alignment. Your equipment will last longer and be more reliable.

Call today for precision laser shaft alignment from our trained technicians.