Condition monitoring plays a hugely significant role when it comes to looking after electric motors. Without it, they could fail unexpectedly—leading to downtime and a potential loss of earnings. While static monitoring is effective at alerting ship operators to weak insulation at the time of a test, it does not identify the root cause. This is where dynamic monitoring comes into play.
Two systems are better than one
Dynamic monitoring is designed to work alongside static monitoring and not just as a standalone solution. The two practices actually observe different factors. Dynamic monitoring provides a more continuous picture of a motor’s health and evaluates its performance during operation. Static monitoring, on the other hand, is usually performed in the docks and gives an indication of what condition a motor is in, in terms of insulation, at that particular time.
Different options for different requirements
Two different types of dynamic monitoring exist. One type is carried out using a portable handheld device that can be taken to different vessels or sites. This is particularly important for service companies that need to visit different customers on-site. Testing of this type is usually conducted at predetermined intervals. The other variant is performed with an installed online system. This provides data on an hourly basis and gives a trend over time—something that is better suited to end customers. Some service providers might consider installing such a system for their customer and take responsibility for analyzing the data and reacting to alarms.
Understanding torque plays an important role
And technology is continuously advancing in this field. The ability to analyze torque is a relatively new addition to condition monitoring. Where once it would have been difficult to find mechanical information hidden within complex modulated current signals, this data can now be easily recorded and interpreted for electrical and mechanical conditions—something that is crucial in understanding machine health.
A trend that’s set to make waves
At present, these systems are becoming more and more popular on modern ships. As insulation deterioration is the main reason for electrical failures in motors, many operators only use static testing to identify this particular problem. However, as the capabilities of dynamic monitoring increase and the market becomes more competitive, the norm is likely to shift.
Indeed, this type of monitoring can identify power circuit problems, voltage level and balance, and total harmonic distortion which could have a detrimental effect on motor health. A further example of something that may lead to motor failure is if a 400kw motor is operating at high load levels but with a normal power quality (assuming there are no other issues), it will run within its temperature design limits. However, if the same motor is operating at 77% load, but with a 3.6% voltage imbalance and harmonic distortion of around 10%, the motor will experience a significant temperature increase due to the power condition. This temperature increase will cause very rapid failure of the winding’s insulation. By uncovering the root causes of failures, dynamic monitoring will increase cost-efficiency through improved maintenance planning and reduced repair costs.
Furthermore, an increasing number of shipping companies are outsourcing monitoring as a service to companies such as SKF. If this continues to prove successful, operators will be more likely to invest in purchasing the technology for themselves.
Overall, dynamic monitoring is emerging in the maritime industry and is being introduced more frequently. SKF offers two products that cover dynamic condition monitoring: the EXP4000 and the NetEP online system. As an advanced method for analyzing motor condition, dynamic monitoring provides an incredibly important service—one that could potentially save shipping companies millions in the years to come.