FAQ
Our maritime experts answer some frequently asked question:
Green Horizons, Issue 3
Q: By how much does the dynamic trim vary from the static departure trim due to increase in speed?
A: There is almost always a significant difference between static trim (measured when vessel is not moving) and dynamic trim (when vessel is moving). The difference varies due to vessel design, loading conditions and naturally due to speed and lots of other variable factors such as weather and water depth. Therefore it is impossible to give a standard conversion. If we "filter out" the effect of other factors than speed, we have measured differences between static and dynamic trim of over a meter. As an example, on one midsized container vessel (close to design draft) we have measured the difference of 0.5m between static conditions and 19kts.
Q: How can we trim when in laden condition? This is impossible! Do you want us to take on board less cargo?
A: In most situations we find that vessels are rarely loaded over 95% of their overall capacity. This provides sufficient scope for Eniram's DTA to achieve the desired fuel savings. In some situations this means that the crew will need to take in additional ballast to be able to implement the trimming to the optimum. Although carrying additional weight in the form of ballast will have an impact on performance, the gained benefit by improving the trim will offset the weight loss multi-fold. Also when a vessel moves it consumes bunker which "releases" space to take on ballast water to trim to optimum. Ideally the loading of the vessel can be done while taking the approximate optimum trim for the next leg.
Green Horizons, Issue 2
Q: What vessel types have Eniram so far performed installations on?
A: Over the past few years, DTA (the Dynamic Trimming Assistant) has been installed on a range of vessel types including container vessels, tankers, cruise ships, RoRo and Ropax vessels. We are also beginning the installation of our first bulk carrier this month.
Q. How useful is the DTA tool for RoRo vessels running 7 hour passages for example?
A: RoRo with 7 hours passage is optimal as you have long enough sailing times, you have also multiple loadings and different drafts for the vessel. The shortest passage times currently are less than 3 hours and we have seen operators get good savings here too. Average savings for our customers is between 2 -3%.
Q: What is the typical return on investment for DTA?
A: This varies, depending on vessel type, as well as journey type and length. However, taking an overall
mean of past installations, the average payback is close to seven months.
Q: Can you quantify the carbon reduction as a consequence of using your technology? If so, how is this done?
A: Yes, we can. We can calculate the reduction in propulsion energy caused by our technology, which enables us to calculate the consequential reduction in fuel consumption. These figures are thus comparable to a certain reduction in CO2 emissions.
Green Horizons, Issue 1
Q: How the trim is measured?
A: Trim measurement is based on attitude sensors provided by Eniram. The attitude sensors are very precise inclinometers which operate to a high frequency and provide the attitude information with 0.01 degree accuracy.
The actual trim of the vessel is then calculated from that attitude information by filtering out the entire periodical (e.g. effect of waves) and instantaneous movements as well as possible hull vibrations.
On vessels over 100 meters in length, multiple attitude sensors are used to eliminate the effect of hull bending and torsion to the trim.
Using these methods for trim measurement provides a unique way to provide accurate and precise trim information for all prevailing conditions even whilst the vessel is sailing. In addition to measuring trim, the attitude sensors provide valuable information about vessel hull movements and its characteristic behaviour both in real time and over longer periods.
Q: What systems are integrated to Eniram VMS and why?
A: The VMS is integrated to several different systems onboard - the IBS (Integrated Bridge System; usually a radar system), and the IAS (Integrated Automation System) being the two most common. This is done to collect data relating to the performance of the vessel, enabling us to determine the optimum trim, or to use it for analysing performance of a vessel or a fleet of vessels.
The Eniram Dynamic Trim Assistant (DTA) calculates and provides the optimal trim in relation to several different variables. To enable such optimization several pieces of information are required, the most critical being the trim, propulsion power and draft. Trim information is provided by Eniram attitude sensors whereas propulsion power and draft require additional data sources.
Propulsion power is usually read from the vessels engine automation but sometimes a separate propulsion measurement system is included. For draft readings the most common method is to read the draft in port from a bubble gauge system and adjust the number while sailing by reading the tank information from a tank soundings system. Both of these can be handled through integration to the vessel's automation system.
Eniram has proven expertise and experience integrating DTA and VMS with vessel automation systems. In the seldom cases where systems are not supported, Eniram engineers will develop an integration interface.
Q: What is the accuracy of the sensors you use?
A: Eniram deploys 2 or more high accuracy (about 0.01 degrees absolute accuracy with the rate of 16 samples per second) sensors which can, in addition to the vessel's attitude, take into account the dynamic bending and torsion. Deflection cannot be measured with a single sensor and therefore dynamic trim readings on a multi-sensor installation are more accurate.
