Alignment, Vibration & Rotating Equipment Condition

Alignment and vibration are major indicators of rotating-equipment condition. Pumps, motors, blowers, mixers, gear drives, and other machines can continue running while misalignment, imbalance, looseness, or bearing wear gradually causes damage.

Operators should recognize changes in vibration, temperature, sound, coupling condition, and equipment position. Early detection can prevent bearing, seal, shaft, and coupling failures.

What Is Alignment?

Alignment means positioning connected rotating shafts so they operate within the required geometric relationship.

Examples include:

• motor shaft aligned with pump shaft;
• motor aligned with blower;
• motor aligned with gearbox.

Why Alignment Matters

Poor alignment can increase:

• vibration;
• bearing load;
• coupling wear;
• seal wear;
• shaft stress;
• energy use.

Parallel Misalignment

Parallel misalignment occurs when two shaft centerlines are parallel but offset from one another.

It is also called offset misalignment.

Angular Misalignment

Angular misalignment occurs when connected shaft centerlines meet at an angle instead of being parallel.

Combined Misalignment

Equipment may have both angular and parallel misalignment at the same time.

Alignment work must correct the total condition, not only one component.

Flexible Couplings

Flexible couplings can tolerate limited movement and small alignment differences.

They do not eliminate the need for proper alignment.

Using coupling flexibility to compensate for poor alignment can shorten:

• coupling life;
• bearing life;
• seal life.

Coupling Inspection

Operators may inspect visible coupling conditions such as:

• damaged elastomer;
• loose hardware;
• abnormal wear;
• missing guard;
• unusual vibration.

Coupling Guards

Coupling guards protect workers from rotating components.

Guards should be:

• installed;
• secure;
• undamaged.

Do not remove guards while equipment is operating.

Soft Foot

Soft foot occurs when one or more equipment feet do not sit evenly on the mounting surface.

When hold-down bolts are tightened, the machine frame may distort.

Effects of Soft Foot

Soft foot can contribute to:

• misalignment;
• vibration;
• bearing stress;
• frame distortion;
• unstable alignment readings.

Causes of Soft Foot

Possible causes include:

• uneven base;
• incorrect shimming;
• debris under equipment foot;
• bent equipment foot;
• damaged grout;
• baseplate distortion.

Baseplates and Foundations

A stable foundation helps maintain equipment alignment.

Inspect for:

• loose anchor bolts;
• cracked grout;
• corrosion;
• movement;
• distortion.

Pipe Strain

Pipe strain occurs when piping places excessive force on connected equipment.

This can happen when piping is:

• misaligned;
• poorly supported;
• thermally stressed;
• forced into position during installation.

Effects of Pipe Strain

Pipe strain can contribute to:

• pump misalignment;
• seal leakage;
• flange leakage;
• bearing problems;
• equipment distortion.

Alignment Can Change After Piping Is Connected

A pump and motor may be aligned correctly before piping is attached.

If piping forces the pump casing out of position, final alignment can change.

Alignment should be checked according to maintenance procedure after piping and equipment installation are complete.

Thermal Growth

Equipment dimensions can change as temperature changes.

This is called thermal growth.

For equipment that operates significantly hotter than ambient conditions, alignment targets may need to account for expected thermal movement.

Cold Alignment Versus Operating Alignment

Equipment may be aligned while stopped and cool, but shaft position can change at operating temperature.

Manufacturer and engineering requirements should be followed for equipment where thermal growth is significant.

Alignment Methods

Maintenance personnel may use methods such as:

• straightedge and feeler gauge;
• dial indicators;
• laser alignment systems.

Precision equipment generally requires more accurate methods than visual alignment alone.

Do Not Align by Eye Alone

Shafts that appear aligned visually may still have enough offset or angular error to cause problems.

Proper measuring tools should be used where required.

Shims

Shims are thin pieces of material placed under equipment feet to adjust position.

Good shimming practices help correct:

• vertical offset;
• soft foot;
• equipment height differences.

Use Clean, Suitable Shims

Poor shimming can create unstable alignment.

Problems include:

• dirty shims;
• damaged shims;
• excessive stacks;
• partial support under equipment feet.

Vibration

Vibration is repetitive mechanical motion around an equilibrium position.

Some vibration is normal in rotating equipment.

The important questions are:

• how much vibration is present;
• whether it is changing;
• what pattern it follows;
• whether other symptoms are present.

Common Causes of Vibration

Possible causes include:

• misalignment;
• imbalance;
• bearing wear;
• looseness;
• bent shaft;
• damaged impeller;
• cavitation;
• hydraulic instability;
• gear problems;
• pipe strain.

Imbalance

Imbalance occurs when rotating mass is unevenly distributed around the shaft centerline.

Possible causes include:

• deposits;
• damaged impeller;
• missing material;
• incorrect assembly;
• uneven wear.

Effects of Imbalance

Imbalance can increase:

• vibration;
• bearing load;
• shaft stress;
• seal wear.

Mechanical Looseness

Loose components can create unstable vibration.

Possible sources include:

• loose anchor bolts;
• loose bearing housing;
• loose coupling components;
• damaged baseplate;
• loose guards or covers.

Bent Shaft

A bent shaft can cause:

• vibration;
• seal leakage;
• uneven bearing load;
• coupling problems.

Shaft Runout

Shaft runout is variation in shaft position as the shaft rotates.

Excessive runout may result from:

• bent shaft;
• damaged surface;
• bearing wear;
• assembly problems.

Runout and Mechanical Seals

Excessive shaft runout can cause seal faces to move excessively and may shorten seal life.

Bearing Wear and Vibration

As bearings deteriorate, vibration may increase.

Other signs can include:

• temperature increase;
• noise;
• lubricant contamination;
• shaft movement.

Vibration Trend

A trend is often more useful than one isolated reading.

For example:

• 2.0 units last month;
• 2.6 units this month;
• 3.4 units this week.

The rising trend may indicate deterioration even if the current value has not yet reached an alarm limit.

Sudden Vibration Increase

A sudden change may indicate:

• debris in rotating equipment;
• broken component;
• loose mounting;
• coupling damage;
• severe cavitation;
• bearing failure.

Gradual Vibration Increase

A gradual increase may indicate:

• bearing wear;
• alignment drift;
• deposit buildup;
• increasing looseness;
• slow component deterioration.

Vibration Direction

Vibration may be measured in:

• horizontal direction;
• vertical direction;
• axial direction.

Different patterns can help trained maintenance personnel identify possible causes.

Axial Vibration

High axial vibration may be associated with conditions such as:

• angular misalignment;
• thrust problems;
• coupling issues.

Radial Vibration

Horizontal or vertical vibration may be associated with:

• imbalance;
• looseness;
• bearing problems;
• hydraulic forces.

Vibration Frequency Analysis

Specialized vibration analysis can compare vibration frequency with machine rotational speed and bearing characteristics.

This work may help identify:

• imbalance;
• misalignment;
• bearing defects;
• gear problems.

Detailed vibration analysis is generally performed by trained personnel.

Operators Still Provide Valuable Information

Even without specialized vibration instruments, operators can identify:

• new vibration;
• increased vibration;
• equipment movement;
• new noise;
• changes after maintenance.

Noise and Vibration Together

Combining observations improves troubleshooting.

Examples include:

• high vibration plus rumbling may suggest bearing damage;
• high vibration plus gravel-like noise may suggest cavitation;
• high vibration immediately after maintenance may suggest alignment or assembly problems.

Temperature and Vibration Together

Increasing vibration plus increasing bearing temperature can indicate a developing mechanical problem.

Possible causes include:

• bearing damage;
• misalignment;
• lubrication problem;
• excessive load.

Motor Current and Vibration Together

Higher motor current with increasing vibration may suggest:

• mechanical binding;
• bearing deterioration;
• misalignment;
• increased driven-equipment load.

Post-Maintenance Vibration

If vibration increases immediately after maintenance, investigate recent changes.

Possible causes include:

• incorrect alignment;
• coupling installation problem;
• improper bearing installation;
• unbalanced rotating component;
• loose bolts;
• pipe strain;
• incorrect assembly.

Post-Maintenance Alignment Checks

Alignment may need to be checked after:

• motor replacement;
• pump replacement;
• bearing replacement;
• coupling replacement;
• baseplate work;
• piping modifications.

Hot Alignment Considerations

Some equipment changes position as it heats during operation.

If the manufacturer specifies hot-alignment targets or thermal offsets, those requirements should be followed.

Pipe Movement

Unexpected pipe movement can indicate:

• hydraulic transients;
• poor supports;
• thermal expansion;
• vibration transfer;
• misalignment.

Resonance

Resonance occurs when a forcing frequency is near a natural frequency of a structure or component.

This can greatly increase vibration.

Resonance problems generally require specialized analysis.

Hydraulic Vibration

Not all vibration is purely mechanical.

Hydraulic causes include:

• cavitation;
• pump operation far from BEP;
• flow recirculation;
• unstable pressure;
• air entrainment.

Aerodynamic Vibration

Blowers and fans can experience vibration related to:

• airflow instability;
• surge;
• fouling;
• imbalance.

Do Not Assume Vibration Means Alignment Only

Misalignment is one common cause, but vibration can result from many mechanical and process conditions.

Troubleshooting should consider the entire equipment system.

Compare Similar Equipment

If two identical units operate under similar conditions, comparison can be useful.

Large differences in:

• vibration;
• temperature;
• noise;
• motor current;

may help identify the abnormal unit.

Use Historical Baselines

Baseline vibration and temperature readings can be recorded when equipment is known to be in good condition.

Future values can then be compared with that baseline.

Condition Monitoring

Condition monitoring may include:

• vibration measurements;
• bearing temperature;
• motor current;
• oil analysis;
• ultrasound;
• infrared inspection.

Predictive Maintenance

Condition trends can be used to plan maintenance before failure.

This supports predictive maintenance by allowing work to be scheduled when deterioration becomes significant.

Do Not Wait for Catastrophic Failure

Severe rotating-equipment failure can damage:

• shaft;
• bearings;
• coupling;
• seal;
• motor;
• connected piping.

Early corrective action may prevent more expensive damage.

When Equipment Should Be Removed from Service

Depending on equipment and facility procedure, immediate shutdown may be appropriate for conditions such as:

• rapidly increasing vibration;
• severe mechanical noise;
• visible equipment movement;
• rapid bearing-temperature increase;
• coupling damage;
• major seal failure;
• suspected shaft failure.

Safe Vibration Inspection

Do not touch or approach rotating components in an unsafe way while checking vibration.

Guards must remain in place during normal operation.

Lockout/Tagout

Alignment, coupling, bearing, shaft, or internal inspection work requires control of hazardous energy.

Possible energy sources include:

• electrical;
• rotational;
• hydraulic;
• pneumatic;
• stored mechanical energy.

Do Not Depend on a Stop Button

A stopped machine can restart because of:

• automatic control;
• remote command;
• process condition;
• control-system logic.

Required energy isolation must be used before maintenance.

Maintenance Records

Useful alignment and vibration records may include:

• asset;
• date;
• vibration readings;
• measurement location;
• bearing temperature;
• alignment result;
• corrective action;
• post-repair readings.

Compare Before and After Repair

Post-maintenance measurements should be compared with pre-maintenance values.

If vibration remains high after repair, the original problem may not have been fully corrected.

Common Alignment and Vibration Mistakes

• Assuming flexible couplings eliminate the need for alignment.
• Ignoring soft foot.
• Forcing piping into position and creating pipe strain.
• Aligning equipment visually without appropriate measurement tools.
• Ignoring gradual vibration increase because equipment still runs.
• Assuming every vibration problem is caused by misalignment.
• Ignoring loose foundations or mounting bolts.
• Failing to check alignment after major maintenance.
• Ignoring thermal growth on equipment where it matters.
• Failing to record baseline vibration values.
• Continuing to operate equipment with rapidly increasing vibration.
• Removing guards or approaching rotating parts unsafely during inspection.

A Practical Rotating-Equipment Condition Check

1. Review equipment operating status and load.
2. Listen for abnormal noise.
3. Observe vibration.
4. Review vibration trend data if available.
5. Check bearing temperature.
6. Review motor current.
7. Inspect coupling and guard condition.
8. Inspect foundation and mounting bolts.
9. Look for evidence of pipe strain or equipment movement.
10. Review recent maintenance or alignment work.
11. Compare with historical baseline.
12. Create a work order or remove equipment from service if deterioration is significant.

A Practical Post-Maintenance Alignment Review

1. Verify correct equipment installation.
2. Check baseplate and mounting surfaces.
3. Check for soft foot.
4. Verify pipe connections are not forcing equipment out of position.
5. Perform required shaft alignment.
6. Tighten mounting hardware according to procedure.
7. Recheck alignment after tightening.
8. Restore guards.
9. Run equipment and observe vibration, temperature, and motor current.
10. Compare post-maintenance readings with baseline values.
11. Document final alignment and operating condition.

What to Remember for the Exam

• Proper alignment reduces bearing, coupling, seal, and shaft stress.
• Parallel misalignment means shafts are offset but parallel.
• Angular misalignment means shaft centerlines are at an angle.
• Flexible couplings do not eliminate the need for proper alignment.
• Soft foot occurs when equipment feet do not sit evenly on the mounting surface.
• Soft foot can cause frame distortion, misalignment, and vibration.
• Pipe strain can pull pumps or other equipment out of alignment.
• Thermal growth can change alignment between cold and operating conditions.
• Alignment should use appropriate measuring tools rather than visual judgment alone.
• Imbalance results from uneven distribution of rotating mass.
• Mechanical looseness, bent shafts, worn bearings, cavitation, and hydraulic instability can all cause vibration.
• Increasing vibration over time can indicate developing equipment deterioration.
• A sudden vibration increase can indicate a new mechanical or hydraulic problem.
• Shaft runout is variation in shaft position as the shaft rotates.
• Excessive shaft runout can damage bearings, seals, and packing.
• Vibration should be evaluated together with temperature, noise, current, and process conditions.
• High vibration immediately after maintenance may indicate alignment, assembly, or mounting problems.
• Condition monitoring can support predictive maintenance.
• Severe or rapidly increasing vibration may justify removing equipment from service.
• Required lockout/tagout must be used before alignment, coupling, bearing, or shaft maintenance.