Regulations & guidelines
Local and International Maritime Laws and Regulations for safe transportation are often supplemented by Industry Standards ('LOC Guidelines for Barge Transportation', 'Noble Denton Guidelines for Marine Transportation', Client Specific Guidelines, etc.) that specify the criteria for design, sea fastening, vessel/barge motions and sea states.
The vessels and cargoes will often also have their own specific limitations and restrictions on maximum allowable forces and vessel/barge motions.
Reality
As mentioned, towage at sea has developed over the years. As a result of thorough preparations, the fast majority of tows arrive safely at their destination.
Sufficient safety margins in the engineering and preparations, improved weather forecasting / weather routing capabilities ensure safe transportation in most cases.
The calculations and preparations are verified by Warranty Surveyors and other Third Party experts.
However!
Once the voyage preparations are completed, the Master of a tug will be guided during the tow by good seamanship and the limits that are defined in the Transportation Manuals: Maximum allowable sea states (Significant Wave Heights) during the voyage Maximum allowable forces on the cargoes, usually expressed in Roll/Pitch angles At sea the Master of the tug is on his own again. He will receive weather/wave height forecasts and routing advice for guidance. It is however well known that on board it is virtually impossible to observe the correct wave heights. 5 Captains and 10 Warranty Surveyors on the bridge of a vessel will give you 15 different answers on what the actual wave height is. The actual Roll/Pitch angles of the tow are visually observed from the tug, and then again only during daylight. At night the motions of the tow are often 'in the dark'.
Although seagoing tows have been common practice for decades now the sector hasn't shown a great deal of technological development.
The Solution
Siri Marine has developed a Tow Monitoring System that works.
- One or more DimMax motion sensors are placed on board of the towed object
- The sensors measure accelerations in 3D with accuracy of 1 mg
- Roll/Pitch angles with an accuracy of 0.05 degrees (static) or < 0.5 degrees (dynamic) are computed and displayed
- A continuous signal from the sensor(s) is transmitted to the tug, where the measurements are displayed 'real-time' and continuously on a PC screen on the bridge
The Master (or Client's Representative) can monitor the 'real-time' accelerations, forces and motions of the tow at all times. The system also displays the history of the accelerations, forces and motions and stores all data for future reporting and/or voyage evaluation. The system is very easy to install and can be operated by the tug's Master and crew.
The system will enable the Master to keep better control over his tow
Alarms for maximum allowable accelerations, forces and Roll/Pitch motions can be generated. The system immediately displays the results of corrective actions
The theoretical assumptions during the engineering and preparation phase of a transport include large safety margins. This is required because the actual motions and resulting forces (=accelerations) on vessel, barge or cargo are not known and may simply differ from the theoretical assumptions. With a Tow Monitoring System installed, the safety margins can be significantly relaxed because the tow motions and forces are known and under control. Increased knowledge on actual tow motions will assist in the (Risk) evaluation and voyage preparations of future projects and transports.
This will result in:
- A significant reduction in cost
- A significant increase in tow performance
- NO increase in risk
Voyage Reporting
There is an increasing demand from Clients, Owners, Operators and Warranty Surveyors for voyage reporting and evaluation. In the event that damage is suspected, or has occurred, a reliable log of the voyage events is essential. SafetyMax Motion Monitoring System already includes the possibility to generate such reports.