Simulation plays an increasingly important role in design, testing, and analysis. By constructing 3D digital models, engineers can better understand and predict the structural integrity associated with a product or structure along with its subsystems, and components. This enhances the validation of designs or helps to determine, and isolate failure related to weakness, stress, or excessive vibration.
Designers, Analysts, or Engineers can then evaluate corrective steps directly on the model. This might include changes to design, substituting material, or adding dampening or stiffening options to reduce noise or vibration. Validating fixes digitally speeds the process significantly while saving time and costs.
It Starts with a Model
Creating these models is as much an art as it is a science. The challenge lies in the level of detail. Because today’s products are a complex construction of assemblies, sub-assemblies, and components, an exact replica of the product is neither practical nor cost-effective. And is generally not necessary.
The model needs to comprehend the important masses and structural stiffness of the major components. Care should be taken to include all of the key components of the system. Many rotating machinery systems may have components hung off of the major system elements such as turbochargers, coolers, air handling systems, controllers, etc.
Equipment Troubleshooting
This simulation approach is especially important in a troubleshooting situation where time is critical. Every minute a piece of machinery is off-line, or a new product introduction program is delayed, represents lost revenue. When issues surface, it becomes critical to quickly develop and simulation model and initiate a diagnostic test.
In such instances, a digital model is often constructed and analyzed. This saves time and allows test engineers to arrive on-site with the fix or with several options in hand. This is especially critical when equipment is in a remote location such as an offshore platform, deep underground, or during restricted travel.
Plant or manufacturer engineers will often explore a variety of modifications to lessen vibration levels. But without a detailed understanding and an opportunity to digitally test alternatives, this is usually a prolonged, expensive, and generally futile exercise in trial and error.
The Data and Model Don’t Agree!
While a basic representative equipment model will generally provide insights and answers, it may be that there are instances where the initial conclusions drawn from that model are not corroborated by data collected in the field. For example, a seemingly insignificant component, excluded from the original model, may interact with the primary elements of the system causing excessive vibration or even failure. As soon as some first look field test data is collected, it should be compared to the simulation model even if all that is available is some basic vibration data.
For example, the initial mode shapes from the simulation should be compared to the vibration data to see if the apparent motion patterns of the system are consistent with the field data. We have encountered situations where a seemingly insignificant mass was significantly affecting the behavior of the system due to the very large vibration amplitude of that mass. The initial simulation model was predicting a bending mode of vibration, but the test data was consistent with roll behavior. Once the mass and the stiffness of its supporting structure were added, the model produced the correct physical behavior seen in the field and it could then be used to develop an efficient fix.
3D digital model construction remains a delicate balance. These models must contain sufficient detail to account for all known variables yet be created quickly and cost-effectively. While this skill set often comes with years of experience there are times when even the most veteran engineer or analyst will have to add the right detail to the model.
A Data-Driven Approach
Digital simulation models provide early insight into solving field equipment problems. These models must have the right level of detail that allows engineers to predict reasons quickly and confidently for, and solutions to, physical problems. This balance is especially critical in troubleshooting scenarios where quick corrective action typically does not allow time to construct overly complex models.
Without question, simulation is a valuable engineering asset. Yet on its own it can sometimes fail to provide the answer. Supplementing 3D digital models with data collected in the field allows engineers to scrutinize simulation results, modify the model, and get to the root of complex problems.