Localized corrosion of mooring chain steel in seawater

Corrosion of mooring chains is regarded as one of main threats to the offshore mooring systems. Localized corrosion is even more dangerous than uniform corrosion because it may not show significant mass loss but it can cause stress concentration and initiate cracks under force, leading to accelerated degradation of mooring chains. Localized...

Connector response of a multibody VLFS subject to wave loading

The energy transition requires us to explore all options for generating non-fossil energy and offshore floating PV( OFPV) energy is gaining momentum with recent developments quite promising. The trend is to combine small individual floaters into a grid using connectors which can be made reasonably flexible. To address the challenges of offshore...

Inexpensive fracture toughness testing of welded steel

In a prior project, TNO has presented a low-cost way of finding frac-ture toughness of base materials for cleavage fracture. That method features a small-scale CTOD specimen, combined with simplified sensors, less fatigue pre-cracking, faster testing, and no need for a temperature chamber. This meth-od has been extended to welds by considering...

Influence of deformation on corrosion of mooring chain steel in seawater

After chain making, proof load testing is used to evaluate if the chains are mechanically qualified. However, proof load testing may bring elongation in the chain links that may affect the corrosion performance of mooring chains in seawater. The influence of deformation and microorganisms on the corrosion properties of chain steel in seawater...

E-inspection: Effect of continuous hull monitoring on ship safety and crew workload

Crewmembers are exposed to high work pressure. Pressure on freight tariffs motivates cost reduction in manning and maintenance, whilst societal developments show decreasing tolerances towards incidents. In conjunction with the developments towards autonomous shipping, the need for continuous and unmanned inspection increases. Considerable...

Coating condition monitoring and the practical application

Corrosion is a main source of degradation of most offshore and ship structures. Especially ballast tanks are vulnerable to corrosion. Protection is pro-vided by coating systems, postponing the onset of uniform corrosion. It is there-fore essential to have a coating system in place and intact. Inspecting ballast tanks for the integrity of the...

A practical approach to ductile material failure during ranking collisions

Ship owners, including navies, are increasingly sailing ice-infested waters and hence need to know the safety of ship hulls regarding collision with ice. Considerable knowledge exists for modelling failure of the hull in impact situations; however, these methods are either insufficiently precise or too expensive for engineering practice. A...

Assessment of raking damage from decelerations measured during a grounding incident

A three degree of freedom external dynamics calculation model for ship grounding has been made, which is used to predict the extent of bottom raking damage and the grounding force with associated decelerations of the ship in terms of surge, sway and yaw. When the ship decelerates, caused by a grounding event, these motions can be logged through...

Grounding damage estimate through acceleration measurements

Instantaneous insight into the structural damage sustained by a ship running aground, can be of great aid in the decision making following such a disaster. It should be possible to distil the extent of structural damage from acceleration measurement data of the entire vessel. Such measurements could possibly even be done using a simple...

Full thickness material tests for impact analysis verification

Traditionally, a failure strain criterion is used in crash simulations in the maritime and offshore industry. More sophisticated methods for multi-axial stress states are based on the Forming Limit Diagram and the Fracture Forming Limit Diagram (FFLD). The diagrams are derived for the steel sheet forming industry, such as car parts. Few tests...

Monitoring coating condition in ballast tanks

Safety of ships and offshore installations is continuously an area of attention for owners, operators and authorities. Standard practice of today requires regular inspections of the hull and machinery. The results of inspections as carried out by various parties may well not be shared amongst each other. This means that enormous amounts of data...

Next generation material failure model for impact analysis

Current practice in crash analysis on maritime structures uses rupture strain as a single parameter failure criterion. The criterion assumes a plane strain condition irrespective of the actual stress state. However ship and offshore structures, exposed to actual collisions or groundings may well deform in different ways and exhibit other strain...