Marine Vibration Monitoring Whitepaper
The Importance of Vibration Monitoring at Sea
Considering the cost of putting to sea, it is well worth investing in vibration monitoring equipment that can help engineers to protect and maximise the performance of marine machinery.
Here, we discuss the challenges facing engineers and offer advice on how to successfully install and use vibration sensing equipment on marine vessels.
Growing Complexity of Marine Machinery
As machinery has become more complex and greater productivity has been demanded from mechanical systems, there has been a corresponding growth in the need for sophisticated vibration sensors to help maximise performance.
This is especially true at sea, where vibration monitoring is a key tool used by marine engineers to manage the availability and maintenance of equipment with rotating shafts, including pumps, motors, fans, gearboxes, and engine systems.
Cost Pressures and the Need for Preventative Maintenance
The cost of putting an oil tanker or a cruise ship to sea has always justified the cost of monitoring. In recent years, pressure has increased on ship owners to meet deadlines while avoiding severe failures that can lead to unscheduled docking or system malfunctions.
Failures such as ventilation fan malfunctions on cruise ships or unplanned repairs on container vessels can generate negative publicity. This increases the importance of applying reliable preventative maintenance techniques.
Managing Vibration in Marine Applications
Designers and engineers have developed tools and practices to prevent vibration and its effects, including alignment tools and automatic lubricators applied during system construction. Components are continually refined to offer greater resistance to vibration.
However, vibration can never be completely eliminated from rotating machinery. As a result, vibration monitoring technology has advanced significantly, with sensors now offering high reliability in a range of resilient enclosures suitable for marine environments.
Causes and Consequences of Vibration at Sea
Vibration monitoring is vital in marine applications because vibration is a leading cause of failure in propulsion systems and auxiliary equipment.
Key causes of vibration include poor alignment of rotating shafts in propulsion systems and turbochargers for main and auxiliary engines.
Vibration monitoring provides early warning of problems, allowing engineers to act before serious damage occurs. Misalignment in fans and motors leads to excessive wear, premature failure, and reduced efficiency. Accessing these components can be difficult and time consuming, leading to reactive maintenance without proper condition monitoring.
Limitations of Traditional Maintenance Approaches
Without condition monitoring, analysing equipment condition often requires dismantling machinery for inspection during docking. This process consumes significant time and manpower.
On large vessels, only a small percentage of equipment can be inspected annually, meaning some components may go unexamined for several years. Dismantling and reassembly can also introduce new defects.
Many marine engineers have observed that a high percentage of defects are maintenance induced, reinforcing the need to reduce unnecessary dismantling.
Advantages of Condition Monitoring in Marine Systems
Condition monitoring, including vibration monitoring of pumps, motors, fans, gearboxes, and engine systems, allows marine engineers to maintain equipment more efficiently with reduced manpower.
Vibration monitoring has become a widely adopted element of marine condition monitoring, alongside oil monitoring and thermal imaging. These techniques protect profits and enhance performance across propulsion, manoeuvring systems, engines, and turbochargers.
Current Vibration Monitoring Technology
Modern vibration sensors and accelerometers operate across wide temperature ranges, measuring high and low frequencies with low hysteresis and high accuracy.
Robust stainless steel housings protect sensors from moisture, dust, oils, and other contaminants, ensuring reliable performance in harsh marine environments.
Types of Accelerometers Used in Marine Monitoring
There are two main categories of accelerometers:
AC accelerometers are used with data collectors to monitor higher value assets.
4 to 20 milliamp accelerometers are used with PLC systems to monitor lower value assets.
Both types can detect imbalance, bearing condition, and misalignment. AC accelerometers can also identify cavitation, looseness, gear defects, and belt problems.
Hansford Sensors offers AC and 4 to 20 milliamp versions of the HS 100 and HS 420 Series, which are intrinsically safe and certified to ATEX and IEC Ex standards.
These industrial vibration sensors are suitable for monitoring pumps, motors, fans, and all other types of rotating machinery in marine applications.
How Accelerometers Work
Accelerometers contain a piezoelectric crystal bonded to a mass. When subjected to acceleration, the mass compresses the crystal, generating an electrical signal proportional to the applied force.
This signal is amplified and conditioned by built in electronics to produce an output suitable for data acquisition or control systems.
Data from accelerometers mounted in key locations can be collected periodically using hand held data collectors or routed via switch boxes to centralised systems for continuous monitoring.
Challenges of Marine Condition Monitoring
Condition monitoring at sea presents unique challenges. Readings taken in port differ from those taken at sea, and heavy weather amplifies these differences.
It is therefore essential to specify the correct accelerometers and apply best practice when managing performance.
Specifying Accelerometers for Marine Applications
To correctly specify an accelerometer, engineers must consider vibration levels, frequency ranges, and environmental conditions such as temperature and exposure to corrosive chemicals.
Additional considerations include whether the atmosphere is combustible, weight constraints, and the absence of earth connections in marine environments.
These challenges have been addressed through careful sensor design. Research, training, and consultation with experienced manufacturers enable engineers to make informed decisions.
Installation Best Practice for Vibration Sensors
Once appropriate sensors have been selected, careful installation is essential to achieve maximum performance.
Accelerometers should be mounted as close as possible to the vibration source. Mounting surfaces should be flat, smooth, unpainted, and larger than the sensor base. Surfaces must be free from grease and oil.
Poor mounting can compromise stability and produce misleading readings that reflect sensor movement rather than machine condition.
Interpreting Data and Improving Performance
After data is collected, vibration information must be analysed and interpreted by onboard engineers or remote monitoring centres.
This analysis builds a clear picture of machine condition and supports the creation of effective maintenance schedules.
With an efficient vibration monitoring system in place, marine engineers achieve higher efficiency and can identify further opportunities to improve machine performance, energy efficiency, and output.
The Growing Importance of Vibration Monitoring at Sea
Vibration monitoring is becoming an increasingly powerful and essential tool. As the cost and consequences of vibration related failures in marine propulsion and auxiliary systems continue to rise, effective vibration monitoring plays a vital role in protecting assets and maintaining operational efficiency.
