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Regulations

In accordance with the IMO Guidelines for Stowing and Securing of Non- Standardized Cargoes, cargoes on board a vessel must be secured to withstand the forces (accelerations) that generally only apply to mid-ocean conditions during severe weather.

For operation in a restricted area, reduction of these figures may be considered, taking into ac¬count the season of the year and the duration of the voyage.

Reality

Ferry's and RoRo vessels usually trade in a restricted area and the duration of the voyage is usually less than 48 hours. High quality weather forecasts for the planned voyage are available from various sources.
A reduction in lashings for trailers, self drive vehicles, Mafi's, and other rolling cargo is sometimes applied; however it is rarely known on board if the actual lashings procedures are in accordance with the actual forces on the cargoes.
As a result large safety margins are applied and there is no method to collect data for future planning of onboard and onshore (ferry / RoRo terminals) operations.

The Solution


Maersk Flanders:
Equipped with Weather Dependant Lashing System

Siri Marine has developed a "Decision Support System" plus approved procedures that will assist the Master to decide on an adequate lashing procedure for each voyage.
Onshore the procedures will assist the Management of Terminals in the planning of personnel and a reduction in personnel cost.
This results in a safe passage without the risk of damage to cargoes and a significant reduction in lashing costs.
The system will satisfy the requirements of the authorities in the use of reduced lashings (Weather Dependent Lashing) during a voyage.

Equipment

Siri Marine has developed a Motion Monitoring System that measures and displays the real-time and historical motions of a vessel (Roll, Pitch and 6 DoF Accelerations)
The system calculates and displays the actual forces on the vessel, cargoes and lashings. Comparison with the maximum allowable forces indicates the safety margins during the voyage. Trends in vessel motions are clearly displayed.
The SiriMarine Motion Monitoring System consists of one or more DimMax Sensors and dedicated software.
In addition to real-time monitoring the system maintains records of the motion monitoring. Logging of GPS and wind data is an additional feature.
The log files can be used for voyage reporting and evaluation.

- Weather Dependent Lashing / Decision Support Guidelines -


Step 1

schieborg
Figure: Typical installation on board a RoRo vessel:
2 DimMax sensors plus 6 calculated Monitoring Position

On board a vessel, trading in a distinct area, the vessel motions are recorded during a period of minimum 3 months.

During the same period a record is kept of the actual weather conditions (Wave and wind data).
Statistical weather information (all-year statistics) for the trade area will be provided.

Step 2


Figure: Typical example of wave height / acceleration measurements

The data will be processed by Siri Marine. Details of all accelerations (forces) encountered during the voyages will be grouped against wave heights. The resulting graphs indicate the maximum measured accelerations (forces) during all measured wave heights.

In the example above the sensor position was in the bow, on the highest car deck. The IMO Guidelines stipulate accelerations of 0.7 g for this position. The highest acceleration measured in Hs = 3 meter was 0.2 g and between Hs 3 – 5,5 meter is was 0.3 g.

Step 3

In close co-operation with the vessel owners and masters a band with maximum wave heights (i.e maximum accelerations) will be defined. The forces on different cargoes will be calculated for this band. This will result in a proposed lashing scheme.

Table: Typical lashing scheme for a RoRo during voyages with Hs 5 (C) meter

Step 4

All data and calculations will be combined in a "Decision Support Guideline", suitable for that particular vessel, or sister vessels.
Weather forecasting services must be employed for the trade area. Daily forecasts, with an outlook for the next 3 – 5 days are to be considered. This Guideline will assist Masters and Terminal Management in their decision on the minimum amount of lashings for the forthcoming voyage.

Step 5

A SiriMarine Motion Measurement System must be permanently installed on board the vessel. In the (unlikely) event the motions (accelerations) exceed the values which have defined the lashing scheme, the vessel Master and Staff receive an alarm and can take corrective action. (Heading Control Procedures)

Results

Decision Support Guidelines have been developed for a number of Ferries and RoRo vessels, trading in the North Sea area.
This has resulted in significant reduction of cargo lashings without any incidents or damages reported.

Table: Typical All-Year statistics of wave heights. In the period April-September a Hs > 2 meter occurs in less than 7% of the time, Hs > 3 meter in less than 2 % of the time.

It has also resulted in a significant reduction in the cost of cargo lashing. The combination with statistical weather information makes it possible for Ferry and RoRo Terminal Management to plan manning requirements for periods of the year.

Figure: Actual Weather Dependent Lashing sailings during 2005 for a RoPax Vessel, trading in the North Sea
Lashing Scheme A: Hs 5 m

Authority Approval

The 'Weather Dependent Lashing' procedures, which have been developed by Siri Marine in close co-operation with vessel owners and crew, have now been approved by various National Maritime Authorities and Classification Societies and are considered unique in the Maritime Community

Services Siri Marine

  • A SiriMarine system, including sensor(s), software, dedicated PC and GPS receiver will be delivered and installed on board
  • During the initial measurement period all data from the voyage will be collected and a "Decision Support Guideline" will be developed for the vessel.
  • Cargo Care training to vessel crews and onshore organizations can be provided, with emphasis on lashing procedures for RoRo vessels and Ferries.
  • "After Sales" services, including advice to masters, shall be provided.
  • Siri Marine aims to be the preferred supplier of Motion Monitoring Equipment on board vessels and provide expertise on Cargo Care and Damage Avoidance

Siri Marine cooperates with Meteo Consult BV as the preferred supplier of weather forecasting services. The combination of SiriMarine (Motions) and SPOS (weather forecasts and routing) provides a "Decision Support System" that is easy to install and use, has excellent user interfaces at a low cost.