Over recent years, the goals of increasing engine efficiency and lowering emissions have been driven by the push for cleaner energy. But no matter the goal, cleaner energy is undoubtedly better for the environment. In the marine industry, cleaner propulsion systems are leading to increased torsional vibration concerns. Left unchecked, torsional vibration can lead to expensive repairs and lengthy downtime. That's why marine operators at any level look to CENTA, a global leader in understanding torsional vibration, as an integral part of their propulsion team.
Torsional vibration is the positive or negative angular displacement of a rotating shaft in a drivetrain, which is superimposed on the steady-state rotation of the system. More simply, torsional vibration refers to the ‘twisting’ movement of the rotating shafts that connect the various pieces of equipment in a drivetrain. This form of vibration can be induced by the driving equipment, the driven equipment, or simply be the result of how the various inertias (rotating masses) and spring stiffness are distributed throughout the drivetrain. Internal combustion cylinder forces and variable frequency drives on motors also contribute heavily to the phenomenon. While the flexible coupling provides many benefits – torque transmission, misalignment compensation, shock & noise damping, etc. - the system designer looks to the flexible coupling as the easiest solution to controlling the torsional response of the system. A properly selected coupling becomes the “spring” that tunes the system to be free of harmful resonance speeds.
Historically oars, sails, steam and low-speed diesel engines powered ships. The early engines and marine transmissions were extremely heavy, low speed systems – so the influences for torsional activity were minimal. As engines moved to modern medium and high speed diesels, and marine transmissions became lighter and lighter, the propulsion systems became more susceptible to torsional vibration.
More recent efforts to cut down on pollution (from coal, fuel oil, and diesel) have led the European Union and the United States to adopt very strict emissions standards for propulsion engines and vessels in general. As the industry transitions to greener alternatives, owners and operators are looking to solutions with alternative fuel sources as well as alternative propulsion system design.
High pressure fuel delivery and changing cylinder combustion pressures of alternate fuels have a large influence on the torsional activity of an internal combustion engine. Adding alternative drive components to the system like motor/generators and power take off/power take in along with the hybrid operating conditions of the power train have a large influence as well. Even more basic systems using variable speed electric motors driving propellers are susceptible to torsional vibration influences.
As the design of marine propulsion continues to evolve, it is more important than ever to have a well qualified expert in torsional vibration like CENTA on your team from the earliest design phase for consultation and calculation resources.
In additional to a proper Torsional Vibration Analysis (TVA) report, onboard vibration analysis is one of the most effective tools for assessing real-time machinery health. Instrumentation and data analysis can help determine the exact nature of a vibration problem and suggest possible solutions.
A proper torsional vibration analysis will study the complete marine propulsion system. The TVA will take into account the connected equipment and its operating conditions, and it will predict stress levels and heat loads on components in the drivetrain. But a TVA report is a theoretical calculation based on supplied information. When you have a clear TVA report, but then experience a vibration issue with the operating equipment, it is important to engage a field expert that can get onboard to instrument and measure the exact system conditions. The collected field data can then be used to calibrate the data supplied for the original TVA report.
CENTA was an early leader in torsional vibration analysis, and they continue to lead the field with their advanced computational techniques. CENTA has been solving complex drivetrain related torsional vibration problems since 1970, having designed and patented numerous coupling and drive shaft products to solve torsional vibration related issues for marine propulsion systems around the world.
CENTA combines their many decades of experience in looking at each unique propulsion system. Understanding the properties of each component along with the operating conditions of the system allows them to present a well calculated system, free of harmful torsional resonance, and ready for many years trouble free operation - be it a traditional, alternative fuel, or hybrid system.
CENTA also offers torsional vibration analysis on existing systems. If you're concerned your new or existing marine application may have potential torsional vibration issues, contact CENTA today.
Palmer Johnson is proud to be an authorized distributor of Centa's industry-leading couplings and drive shafts. Whether you need spare parts or are interested in a new application, we are your top source for all Centa coupling & drive shaft needs.
This article was originally published by Regal Rexnord.
