Vibration Measurement

Vibration measurement, verification of machinery behaviour, monitoring, and troubleshooting activities are among the main activities of ØDS.

We have experience with identifying and solving machinery problems on site. Today, we are one of the most respected independent consulting companies in the world with state-of-the-art tools to measure vibrations.

• Centrifugal Compressors and Pumps
• Axial Compressors
• Gas and Steam Turbines
• Motors and Generators
• Turbo-Expanders
• Reciprocating Machines
• Gears
• Balancing
• Performance Mapping
• Operation Deflection Shape Analysis
• Modal Analysis
• Transient Vibration Analysis
• Troubleshooting

Torsional Vibrations

Diagnostics is Difficult
It can be difficult to identify why machines vibrate excessively or fail, even for experienced engineers. In some cases, it is a veritable detective’s work to determine the cause of unusual vibrations.

The difficulty arises because high vibration can be due to either high excitation or high flexibility, as is the case with resonance.

Furthermore, turbomachinery is often custom-built, and new technologies are continuously introduced. The downside is increased risk of human errors and sometimes the introduction of new failure modes.

Troubleshooting
Troubleshooting requires a combination of information from several sources, including the vibration monitoring system, the process control system and the operators. Often a limited test programme will be necessary, e.g. measurements during coast-down, variation of bearing temperature and changes of the process parameters within the limits of the site production schedule.

Often only one chance is offered to perform the measurements. The best results are obtained with an expert on-site and potential back-up for discussion and analysis from off-site. ØDS has the size and experience that allow swift expert mobilisation with full range measuring equipment and off-site backup.

Balancing and Alignment
Vibration problems are often caused by imbalance or misalignment. Successful solutions to these problems involve knowledge of:

• Multiple plane (dynamic) balancing
• Critical speeds
• Hydraulic imbalance
• Thermal effects and shaft bow

Performance Mapping
Increasingly, turbomachinery has a wide range of operating conditions. It is therefore important to map the relationship between vibrations and operating parameters, e.g.,

• Pressure and temperature
• Flow rate
• Power
• Gas/fluid composition

Seeking the true operating envelope (e.g., minimum stable flow and stonewall on centrifugal compressors) helps to prevent unnecessary alarms and trips.

Remote Access Monitoring
Some vibration problems develop slowly and can therefore be detected and diagnosed by use of a condition monitoring system. ØDS performs this type of work for several clients by remote access and/or database transfer.

Experience
The ØDS Machinery Dynamics Group consists of mechanical engineers who hold M.Sc. or Ph.D. degrees in rotor dynamics, fluid dynamics or solid mechanics.

ØDS’ assignments vary between in-depth design verification studies, string test participation and on-site troubleshooting activities. We take pride in combining theoretical and practical knowledge of both components and machinery, and have experience with a large variety of turbomachinery problems.

Resources
ØDS has a complete selection of vibration measurement and analysis equipment.

• Multi-channel digital recorders (up to 64 simultaneous channels)
• Multi-channel FFT analysers
• Every type of sensor and transducer
• Modal shakers and large calibrated impact hammers
• Telemetry (please refer to ØDS’ note on torsional vibrations)

Furthermore, we have developed in-house signal analysis capabilities for special assignments (e.g., wavelet transformation and rain flow counting).