When a piece of equipment fails, the immediate problem is usually easy to see. A bearing has failed. A weld has cracked. A bracket has broken. A shaft is vibrating excessively. The natural response is to repair or replace the damaged component and get the equipment running again.
But what if the failed component is a symptom rather than the actual problem? In these cases, replacing the damaged part may restore operation temporarily, but unless the underlying cause is identified, the same (or different) failure may reoccur.
Beyond the Failed Component
Consider a cracked mounting bracket. At first glance, the solution might seem to simply replace the bracket or redesign it using thicker material.
But why did it crack? Perhaps the bracket was subjected to loads that were higher than expected. Maybe vibration from another component created a resonance condition. The equipment could be experiencing unexpected movement during certain operating conditions. Or the bracket may have been subjected to thousands or millions of load cycles that eventually produced a fatigue crack. Fixing the bracket without understanding what caused the failure will just postpone the problem.
Measure First, Diagnose Second
Depending on the equipment and the suspected failure mechanism, engineers may measure vibration, strain, acceleration, displacement, force, pressure, temperature, or other operating parameters. These measurements provide a clearer picture of what’s happening in the real world.
Engineering calculations and simulations are generally based on assumptions about loads, constraints, materials, operating environments, and other variables. Real machines don’t always behave exactly as expected. Field testing can reveal loads that weren’t anticipated during design, vibration at unexpected frequencies, structural movement, transient events, or operating conditions that only occur occasionally.
Instead of asking only, “Why did this component break?” engineers can begin asking more useful questions: What forces were acting on it? When did the highest stresses occur? Is vibration contributing to the problem? Is the structure responding differently at certain speeds or operating conditions?
Separating Symptoms From Causes
One of the biggest challenges in troubleshooting mechanical problems is distinguishing a symptom from its source. Excessive vibration, for example, could be caused by imbalance, misalignment, looseness, resonance, bearing problems, structural flexibility, or an external excitation source. A fatigue crack might originate from excessive stress, but the reason for that stress could be located somewhere else in the system.
This is why replacing parts based solely on visible damage can become expensive. Organizations may repeatedly repair the same equipment without eliminating the condition that is producing the failure. A combination of field measurements, vibration analysis, strain measurements, fatigue analysis, and finite element analysis can help engineers connect what they see physically with what is happening dynamically and structurally.
Turning Test Data Into a Solution
Collecting data is only part of the process. The real value comes from understanding what that data means. Once the failure mechanism has been identified, engineers can evaluate potential solutions with much greater confidence. That might mean modifying a structure, changing stiffness, reducing vibration, relocating a component, altering operating speeds, improving isolation, or redesigning a part.
Most importantly, the solution addresses the cause rather than simply repairing the damage. At 6D Testing & Analysis, we help engineering teams investigate difficult mechanical and structural problems using real-world testing and engineering analysis. When equipment fails—or simply isn’t behaving as expected—the right measurements can help uncover what’s really happening.
Example: Recurring Oil Pan Cracks on Large High Speed Gas Engines
Cracks were developing in oil pans of several Caterpillar engines used to drive reciprocating pumps at a gas pumping facility. Removing an oil pan for inspection and replacement from such an inaccessible, large installation required special precautions and extensive cribbing. Because the engine design had been in service for many years, it was a mystery why cracks were suddenly developing after less than 70 service hours.
Read this case study to learn how 6D engineers were able to determine and correct the root cause of this issue.
Find out why it failed.
Contact 6D Testing & Analysis to learn how field testing, vibration analysis, strain measurement, fatigue analysis, and FEA can help identify the root cause and guide you toward a more effective solution.