Stability conditions (watercraft)
Encyclopedia
Stability conditions is the term used to describe the various standard loading configurations to which a ship
Ship
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...

, boat
Boat
A boat is a watercraft of any size designed to float or plane, to provide passage across water. Usually this water will be inland or in protected coastal areas. However, boats such as the whaleboat were designed to be operated from a ship in an offshore environment. In naval terms, a boat is a...

, or offshore platform may be subjected. They are recognized by classification societies such as Lloyd's Register
Lloyd's Register
The Lloyd's Register Group is a maritime classification society and independent risk management organisation providing risk assessment and mitigation services and management systems certification. Historically, as Lloyd's Register of Shipping, it was a specifically maritime organisation...

, American Bureau of Shipping (ABS)
American Bureau of Shipping
The American Bureau of Shipping is a classification society, with a mission to promote the security of life, property and the natural environment, primarily through the development and verification of standards for the design, construction and operational maintenance of marine-related facilities...

 and Det Norske Veritas. Classification societies follow rules and guidelines laid down by International Convention for the Safety of Life at Sea
International Convention for the Safety of Life at Sea
The International Convention for the Safety of Life at Sea is an international maritime safety treaty. The SOLAS Convention in its successive forms is generally regarded as the most important of all international treaties concerning the safety of merchant ships.- History :The first version of the...

 (SOLAS) conventions, the International Maritime Organization
International Maritime Organization
The International Maritime Organization , formerly known as the Inter-Governmental Maritime Consultative Organization , was established in Geneva in 1948, and came into force ten years later, meeting for the first time in 1959...

 and laws of the country under which the vessel is flagged, such as the Code of Federal Regulations
Code of Federal Regulations
The Code of Federal Regulations is the codification of the general and permanent rules and regulations published in the Federal Register by the executive departments and agencies of the Federal Government of the United States.The CFR is published by the Office of the Federal Register, an agency...

.

Stability is normally broken into two distinct types: Intact and Damaged

Intact stability

The vessel is in normal operational configuration. The hull is not breached in any compartment. The vessel will be expected to meet various stability criteria such as GMt (metacentric height), area under the GZ (righting lever) curve, range of stability, trim, etc.

Lightship

The vessel is complete and ready for service in every respect, including permanent ballast
Sailing ballast
Ballast is used in sailboats to provide moment to resist the lateral forces on the sail. Insufficiently ballasted boats will tend to tip, or heel, excessively in high winds. Too much heel may result in the boat capsizing. If a sailing vessel should need to voyage without cargo then ballast of...

, spare parts, lubricating oil, working stores, plus an allowance for the crew and their personal effects. All normally flooded spaces such as sea chests and cooling systems are considered but the vessel has no fuel, drinking or washing water, cargo, or any other load item.

Light operating or light displacement

Along with all the Lightship loads, the vessel has all systems charged meaning that all fresh water, cooling, lubricating, hydraulic and fuel service header tanks, piping and equipment systems are filled with their normal operating fluids. Crew and effects are at their normal values. Consumables (provisions, potable water and fuel) are at 10% full load. Ammunition and/or cargo is not included (0% of full load).

Full load departure or full displacement

Along with all the Lightship loads, the vessel has all systems charged meaning that all fresh water, cooling, lubricating, hydraulic and fuel service header tanks, piping and equipment systems are filled with their normal operating fluids. Crew and effects are at their normal values. Consumables (provisions, potable water and fuel) are at 100% capacity. Ammunition and/or cargo is at maximum capacity. The vessel is at its limiting draft
Draft (hull)
The draft of a ship's hull is the vertical distance between the waterline and the bottom of the hull , with the thickness of the hull included; in the case of not being included the draft outline would be obtained...

 or legal load line.

Standard condition

This is only for military vessels. Along with all the Lightship loads, the vessel has all systems charged meaning that all fresh water, cooling, lubricating, hydraulic and fuel service header tanks, piping and equipment systems are filled with their normal operating fluids. Crew and effects are at their normal values. Consumables (provisions, potable water and fuel) are at 50% capacity. Ammunition and/or cargo is at 100% capacity. This condition is normally used for range and speed calculations.

Light arrival

Along with all the Lightship loads, the vessel has all systems charged meaning that all fresh water, cooling, lubricating, hydraulic and fuel service header tanks, piping and equipment systems are filled with their normal operating fluids. Crew and effects are at their normal values. Consumables (provisions, potable water and fuel) are at 10% full load. Ammunition and/or cargo is at 100% capacity.

Damaged stability

  • Damaged
The vessel in the assessed "Worst Intact Condition" is analytically damaged by opening various combinations of watertight compartments to the sea. The number of compartments and their location are dictated by IMO
International Maritime Organization
The International Maritime Organization , formerly known as the Inter-Governmental Maritime Consultative Organization , was established in Geneva in 1948, and came into force ten years later, meeting for the first time in 1959...

 regulations, SOLAS
International Convention for the Safety of Life at Sea
The International Convention for the Safety of Life at Sea is an international maritime safety treaty. The SOLAS Convention in its successive forms is generally regarded as the most important of all international treaties concerning the safety of merchant ships.- History :The first version of the...

 conventions, or other applicable rules. Typically these conditions are identified by the compartment(s) damaged ex: "Hold #3 and Water Ballast Tank 4 Port"

See also

  • Naval architecture
    Naval architecture
    Naval architecture is an engineering discipline dealing with the design, construction, maintenance and operation of marine vessels and structures. Naval architecture involves basic and applied research, design, development, design evaluation and calculations during all stages of the life of a...

  • Hull (watercraft)
    Hull (watercraft)
    A hull is the watertight body of a ship or boat. Above the hull is the superstructure and/or deckhouse, where present. The line where the hull meets the water surface is called the waterline.The structure of the hull varies depending on the vessel type...

  • Society of Naval Architects and Marine Engineers
    Society of Naval Architects and Marine Engineers
    The Society of Naval Architects and Marine Engineers is a professional society that provides a forum for the advancement of the engineering profession as applied to the marine field...

  • Ship stability
    Ship stability
    Ship stability is an area of naval architecture and ship design that deals with how a ship behaves at sea, both in still water and in waves. Stability calculations focus on the center of gravity and center of buoyancy of vessels and on how these interact....

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