Severe Wind and Rolling affecting hull strength & stability of Container ship

The purpose of IMO severe wind and rolling criterion is to evaluate the vessel’s ability to survive severe beam seas and wind. Such a situation may be assumed to occur should the vessel lose steering or propulsive capability in a storm, in which case it will likely end up wallowing in beam seas. If the vessel can roll freely back to leeward under the combination of all of these forces (assumed wind, beam seas, and vessels momentum gathered in a roll) without rolling past its range of positive stability (capsize point), or taking on water through open down flooding points (such as the Engine room air inlets), it passes the requirement.

Fig: Loss of containers due parametric rolling

Most cargo stowage and stability calculation software provide Alarms / Highlights for stability conditions not complying with IMO severe wind and rolling criterion. Compliance must be confirmed.

Forces on containers during transportation

Cargo transportation often involves different modes of transport, by road, rail, and/or sea. Often, combined cargo transport units like containers will set out by the road, continue by sea and perhaps conclude as rail freight. Cargo transported by combined means must be stowed and secured so as to withstand the forces involved in all the modes of transport used. In adverse weather, outboard and partially exposed container stacks may be exposed to wind. The degree of force depends on the velocity and direction of the wind, and the profile of the stacks affected. The higher the stacks, the greater the surface area and consequently force generated.

When container ships are exposed to heavy weather, accidents often involve overturned container stacks in the aft stacks. This is despite acceleration at the fore-end being greater than in the aft.

Aft stack problems

One reason for the problems with aft stacks can be that, due to the the required line of sight from the bridge, stack stowage height aft of the superstructure is greater than it is to the fore. Another reason may be that large, wide container ships can suffer stern slamming when there are following or quartering seas. This can drastically raise forces on the securing equipment in the aft container stacks. The intensity of acceleration and forces during sea transports is affected by different types of seas. Sheltered waters, shallow seas, and deep oceans cause different levels of acceleration.

Early avoidance essential

To avoid excessive acceleration and forces, course and speed may have to be adjusted to ease the ship’s motion in heavy seas. Early avoidance of adverse weather and sea conditions is always recommended. Taking into account the actual stability conditions, it may also, be necessary to ballast or de-ballast the the ship, thus improving its behavior and avoiding excessive acceleration. Factors for consideration:

Weather and sea conditions.
Excessive transverse metacentric height values.
Incorrectly stowed containers.
Overloaded (under-declared) containers.
Excessive container weight.
Deteriorated securing equipment.
Defective container structure.
Cargo securing arrangements.
Loss of equipment and containers over board, lashing by stevedores, positioning of securing equipment.

Other relevant factors:

Non-standard securing equipment.
Improperly maintained securing equipment.
Inadequate supply of correct securing equipment.
Overloading of securing equipment.

Ship Encountering Parametric Roll In A Seaway
The term parametric roll for a container ship is used to describe the phenomenon of large unstable roll motion suddenly occurring in the head or stern seas. Due to its violent nature, the large accelerations associated with the onset of the parametric roll cause concern for container ships' safety. Possible consequences include loss of containers, machinery failure, structural damage, and even capsize....

Action by vessels navigating in congested water
Ships navigation is referred to the voyage practices, focusing on the process of monitoring and controlling the movement of the ship from point "A" to point "B". Choosing the most optimum route while transiting through traffic-congested water is even more challenging. Specifically, due to the presence of many vessels in the vicinity, a repeated risk of collision exists....

Action by vessels navigating in an area of restricted visibility
Ship navigation under restricted visibility circumstances is one of the most challenging tasks while accomplishing a safe voyage. The visibility is mentioned as restricted in cases that have been observed fog, heavy rain, or dust storm, all hazardous conditions to navigate. Ship navigation in such conditions doubles the likelihood of a collision or grounding. It calls for the use of specialized equipment and requires some actions to be taken by the time the ship's officer gets information of relevant weather conditions......

How to confirm stabilty condition?
In the northern hemisphere during hurricane season, extreme weather is a common phenomenon. A big storm can run havoc even on the largest containership by tearing off its deck lashings. Most modern ships are designed to survive in harsh conditions and stay on schedule. Nevertheless, facing storms at sea is routinely an unavoidable part of life at sea. Each year substantial weather damages incur huge financial liabilities on ship operators. ......

How to maintain watertight integrity?
To maintain Water tightness, Seaworthiness, Fire integrity and Security of the vessel, it is important ships personnel ensure all openings to hull below water line and above waterline ( weathertight & watertight doors etc.) are adequately secured. ......

Guide to watch officer for ships navigation ?
Bridge watchkeeping is the most critical activity conducted at sea. Upon the watchkeeper's diligence rests the safety and security of the ship, her entire crew, the cargo, and the environment. It is a demanding activity, requires support, encouragement, motivation, self-discipline and a high standard of professionalism. Ships master must ensure that all watchkeepers understand the use of safety related equipment, prior to them keeping a watch......

Heavy weather countermeasures for prudent navigator
Encountering extreme weather conditions at sea along major trade routes is a common phenomenon. Depending upon geographical location and seasonality of revolving tropical storms, a ship, therefore, need to prepare well to survive in harsh conditions. Both heavy weather and tropical storms demand of crew's preparation and immediate response.

How to navigate vessel safely in heavy seas ?
Encountering extreme weather conditions at sea along major trade routes is a common phenomenon. Depending upon geographical location and seasonality of revolving tropical storms, a ship, therefore, need to prepare well to survive in harsh conditions. Both heavy weather and tropical storms demand of crew's preparation and immediate response.

Meeting rough sea conditions by containerships
In heavy weather conditions where it is unsafe for ship crew to venture out on the deck for purposes of checking deck cargo securing, Master shall consider his ship handling options and heave to if required. The aim should be ensuring the safety of the vessel and its cargo. .....

Checklist for calculating stability and hull strength for cargo ship
In heavy weather conditions where it is unsafe for ship crew to venture out on the deck for purposes of checking deck cargo securing, Master shall consider his ship handling options and heave to if required. The aim should be ensuring the safety of the vessel and its cargo. ......

Container Ship navigation - passage planning guideline
Before proceeding to sea, the Master shall carefully check the Passage Plan, made after receiving the voyage instruction from the Charterer or the Company. Passage plan shall be made from berth to berth acting on the principle of Safety-first, while also taking operating efficiency into consideration. The passage plan shall be prepared normally by the Second Officer, signed for approval by master and for understanding by all officers, before departure.Based on this Guide, the Master shall collect necessary information and review the Plan including Emergency Contingency Plans.

Navigation in cold districts and countermeasures
Ocean water freezes just like freshwater, but at lower temperatures. Freshwater freezes at 32 degrees Fahrenheit, but seawater freezes at about 28.4 degrees Fahrenheit, because of the salt in it. Due to the presence of many hostile conditions, any merchant ship, while entering a freezing sea area, significant challenges are being encountered concerning safety and reliability of navigation.

Safe anchoring - planning and operational guidance for cargo ships
For the safety of the ship, strict anchor watches must be kept when the ship is at anchor. The principal reason for keeping anchor watches by one or more sailors is to maintain the safety and security of the vessel. Anchor watches to be maintained following the Masters's orders. This should include regular inspection of lead and weight on-chain.

Anchor watch check item - deck officers guideline ....

How to deal with a damaged anchor? ....
When a part of the anchor chain breaks, it may be due to wear and corrosion or to over-stressing of its weakest part. Typically a ship owner arranges for anchors and chain damage inspection in a dry-dock, full range length, and can take a note on weakest links. A common defect is loose studs that reduce chain strength significantly. In all cases, the class surveyor should be consulted, and defective/ wasted chain be renewed as per surveyors' strict guidelines. It is a ship owner's routine expenditure for anchoring arrangement.

How to recover a lost anchor ? ....
After the anchor and chain are lost, the Master should make an initial report to the management company. After that, from time-to-time, the Master should report further developments. The Master should report the circumstances that led to the loss of the anchor and chain so that the Company can determine whether the general average is affected.

What is stranding ? Investigation of possibility of self-refloating and urgency of danger ....
Stranding means when a vessel has run aground, it is accidental. In consequence, the double bottom area of the vessel will probably suffer considerable damage, especially if the ground is rocky. This is physically the same action as beaching, but with the significant difference that beaching the vessel is an intentional action and under comparatively controlled conditions, whereas stranding is accidental.

What are the emergency procedures for loss of anchor and chain? ....
After the anchor and chain are lost, the Master should make an initial report to the management company. After that, from time-to-time, the Master should report further developments. The Master should report the circumstances that led to the loss of the anchor and chain so that the Company can determine whether the general average is affected.

Securing your vessel for sea passage - when to check and what to check
Many maritime accidents are caused by the mistakes of ship personnel for inadequate sailing preparation. To avoid recurrences of the fatality deck and engine department must be well prepared before a vessel’s departure for a voyage at sea. These arrangements may include many complexities, and this is the reason why a bunch of things should be recognized and prepared delicately to ensure a smooth voyage passage and safe navigation.

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IMO Intact Stability Criterion for containership

Corrected GoM for Hull Strength and Stability of containership

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