Schedule reliability
General information
RoRo's, RoPax, Container vessels and cruise vessels sail according a fixed schedule. Therefore, it is important to know if these vessels are able to keep their schedule.

Wind, waves and current cause additional resistance with respect to the calm water resistance. This so-called added resistance, increases the power demand. If the demand is higher than the capacity of the engine the ships speed decreases. This is called "involuntary" speed loss. The ships master can also reduce the velocity because of comfort and (fear for) damage to ship and cargo. This is called "voluntary" speed reduction.This comfort and damage issues can be related to slamming, green water and whipping and springing of the hull.

Services & Activities
Schedule reliability can be assessed by means of scenario simulations. During these simulations (round)trips are simulated stepwise. Each trip is simulated for hundreds of times and for several years. At each time step the maximum sustained speed is calculated accounting for engine limitations and the actual weather conditions. Furthermore the ship behaviour is evaluated and this input is used to asses "voluntary" speed reduction.
The duration of each trip is obtained for every voyage. The long term distribution of these durations is used to obtain the required service margin (see figure above). It also can account easily for seasonal variations.

Facilities & Tools
Schedule reliability is assessed by the Safetrans and Gulliver software tools. Details on these tools can be found here.

Most recent Schedule reliability papers presented by MARIN:
(complete overview of papers can be found under Publications)

Significant upgrade of Anti Roll Tank (ART) design services
Michiel Gunsing, Bastien Abeil & Nicolas Carette, MARIN Report, 2013

Hydrodynamic software suites make design concept evaluation more efficient
Arno Bons & Arie de Wit, MARIN Report, 2013

Retrofitting for energy savings and emissions reduction
Patrick Hooijmans, MARIN Report, 2013

OBELICS JIP successfully achieves goals
Ron Schoon & Eelco Frickel, MARIN Report, 2013

First images of cavitation and ventilation in waves
Gerco Hagesteijn & Joris Brouwer, MARIN Report, 2012

Most recent Schedule reliability articles written for MARIN Report:
(complete overview of articles can be found under Publications)

Significant upgrade of Anti Roll Tank (ART) design services
MARIN has recently invested in new methodologies and modern tools to improve its services related to ART design.

Hydrodynamic software suites make design concept evaluation more efficient
To support designers and engineers in evaluating design concepts more efficiently, MARIN has developed the hydrodynamic suites QSHIP and QPROP.

Retrofitting for energy savings and emissions reduction
When it comes to fuel efficiency, people usually think about new designs that should be more fuel efficient. However, potentially there is a huge existing fleet, which could be optimised in respect of fuel consumption...

OBELICS JIP successfully achieves goals
OBELICS, the Joint Industry Project on Operability of Ballasting and lifting operations of Extreme Loads with Integrated hydro dynamiCS, was just rounded off after two years of intense cooperation.

First images of cavitation and ventilation in waves
History was made on May 22 when the first-ever cavitating and ventilating images appeared on the monitors at MARIN’s new Depressurised Wave Basin.

Contact
For more information on how MARIN can help your organisation with schedule reliability assessments, please contact:

Seakeeping Department

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