Stability

Question 1

Intact stability requirements.

Initial GM
Max GZ
Angle of maximum GZ
Area upto 30°
Area upto 40°
Area between 30°~ 40°

Answer 1

At least 0.15
Not less than 0.20m
Not less than 30°
Not less than 0.055mr
Not less than 0.09mr
Not less than 0.03mr

Question 2

1) Displacement
2) Lightweight
3) Deadweight
4) Air Draft
5) Lightship

Answer 2

1) The weight of the ship and its contents, the value will vary according to the ships draft in tonnes.
2) The weight of the ship in tonnes. The mass of an empty ship, without stores, fuel, water, crew or effects.
3) The mass of the cargo, fuel, water, stores, etc. The difference between Displacement and lightweight ie, Displacement = lightweight + Deadweight. Usually considered the maximum capacity the ship can carry.
4) Air Draft = height from keel - mean draft. The part of the ship out of the water.
5) Includes steel structure of the vessel and ballast, spare parts, stores but no fuel, drinking or washing water or cargo.

Question 3

What is?:

Metacentric Height (GM)

Centre of Gravity

Centre of Buoyancy

Answer 3

GM is the distance between the centre of gravity (G) of a ship and its metacenter (M).

The point at which all of the mass of the ship may be assumed to be concentrated.

An upward vertical force equal to the weight of the water displaced.

Question 4

1) Gross Tonnage
2) Net Tonnage
3) Fresh Water Allowance

Answer 4

1) (GT) Related to the ships overall internal volume. It is calculated based on the moulded volume of all enclosed spaces of the ship.
2) (NT) is a calculated representation of the internal volume of a ships cargo holds.
3) FWA is the number of (mm) by which the mean draft changes when a ship passes from salt water to fresh water or vise versa while floating at loaded draft.

FWA = Summer Displacement/
4 x TPC

Question 5

A)Heel

B)List

C)Loll

D) Trim

Answer 5

A ship is said to be heeled when she is inclined by external forces, eg wind, waves, alteration of course at high speed etc

A ship is said to be listed when she inclines because of internal forces within the ship, such as an off center weight, Ballast water or sea water sloshing to one side of the ship causing free surface effect. List is a positive stability condition caused by an off centre weight.

Loll is a negative stability condition. It is the angle a ship with initial negative GM will lie at rest in still water where the righting lever is zero. The new angle which the ship will oscillate instead of her normal upright position.

The difference between the forward and aft draft.

Question 6

1) Centre of flotation

Formula for:

2) FWA
3) DWA

Answer 6

1) Geometric Centre of the water plane area = TMD

2) Displacement /
4 × TPC

3) (SWD - DWD) x FWA/
25

Question 7

What is? :

Stowage factor

Broken stowage

What is freight

What is Deadweight

What is measurement cargo

In what ways is cargo / freight charged?

How is stowage factor calculated?

Answer 7

Stowage factor is the ratio of weight to Stowage space required. It is the space occupied by a unit of weight of cargo. Expressed in m³.

Broken stowage is expressed as the % of the volume of cargo and the cargo space used.

Freight is the charge made by the owner or the ship for carriage of cargo.

Deadweight is the term used when the freight cargo is charged per tonne weight - for cargo with low stowage factor. Its easier to work out the weight and how much of a particular type of cargo is carried for cargo with low stowage factor like iron ore or a liquid which takes to shape of the space it occupies. When loaded to full capacity.

Measurement cargo is the term applied when freight is charged by the unit volume - for cargo having a high stowage factor. Cargo with SF above 1.2. A cargo whose transportation cost is calculated on the basis of its dimensions rather than its weight. For example, if acargoismeasuredin bales rather than tons, it ismeasurement cargo.

Stowage factor and measurement cargo.

Theformulaforcalculatingastowage factoris one long ton x volume of ship in cubic feet.
Divided by the cargo weight.

Question 8

What is Tonnes per centimetre immersion (TPC)?

What are the formulas for TPC for salt water and Dock water?

Answer 8

For any draft the mass which must be loaded or discharged to change a ships mean draft in salt water by 1 centimetre.

TPC sw= Waterplane Area x density of water/
100

TPC dw = R.D of DW x TPC sw/
1.025

Question 9

Flashpoint

Volitle

Auto ignition

Answer 9

Flashpoint is the lowest temperature that a liquid gives off sufficient gas to form flammable gas mixture near the surface of the liquid.

Volitle means a gas that has flashpoint below 60°

When the liquid reaches a certain temperature causing it to ignite.

Question 10

Marpol special areas

Annex 1 ~ 6

Answer 10

Annex 1. Oil) Baltic, Black, Red, Med seas. Gulf and Arctic areas. NW European waters, Oman Arabian Sea and Southern African waters.

Annex 2. NL substances) Antarctic area.

Annex 4. Sewage) (For Passanger ships only), Baltic as no reception facilities anywhere else

Annex 5. Garbage) Same as Annex 1 with carrabbean region and Gulf of Mexico.

Annex 6. Air emissions) Baltic and North Sea. North America USA and Caribbean Sea are ECA areas for NOx and Sox and PM.

Question 11

Annex 1 Oil pollution.

IOPPC with Form A: - A record of Construction and Equipment for non Tankers.
Oil Record Book part 1 Machinery space operations.

SOPEP: shipboard Oil Pollution Emergency Plan.

Non Tankers over 400GT

Discharge criteria of oily water from bilges and machinery spaces :

Answer 11

Not permitted inside a Special Area.

Outside a Special Area.

1. The ship is en route
2. The oil content does not exceed 15ppm.
3. The ship has oil filtering system (oily water separator) if 400-10,000 GT
4. Not from cargo spaces or pump room.
5. Not mixed with cargo residues.

If above 10,000 GT. &
If in a special Area must have:

The addition of an alarm and auto shut down (ODME) which activates when 15ppm is exceeded.

Question 12

Annex 1 Oil pollution.

IOPPC Form B - Record of Construction and Equipment for Tankers.
ORB Part 1 and (2. Cargo and Ballast operations)

Tankers over 150 GT

A tanker may not discharge any oil or oily mixture from cargo tanks (sludge) or pump room bilges unless :

Answer 12

1. The tanker is en route.
2. It is not within a special area.
3. The discharge rate of effluent is not more than 30 litres per nm.
4. The discharge must not exceed 1\30,000 of the Vol of cargo.
5. It is more than 50 miles from the nearest land.
6. The ship must have oil discharge monitoring equipment (ODME)

Not permitted in a Special Area.

Question 13

Annex 4 Sewage

ISPPC : International Sewage Pollution Prevention Certificate.

Only special Area for Sewage is the Baltic and only for Passanger ships

Discharge criteria.

Answer 13

For Cargo ships:
Ships may discharge comminuted and disinfected Sewage, using an approved system more than 3 miles from the nearest land. (Sewage Treatment Facility).

If Sewage is untreated, not less than 12 miles from land. (Holding Tank.)

Sewage to be stored in holding tanks or type approved Sewage treatment (As shown in ISPPC) plant but should not be discharge instantaneously.

It should be discharged at a moderate rate when ship is en route at not less than 4 knots, the effluent should not discolour the water or have visible or floating solids.

Passanger ships can not discharge in the Baltic Sea. Must use reception facilities.

Question 14

Annex 5 Garbage.

Must have :
GRB: Garbage Record Book
GMP: Garbage Management Plan

Discharge criteria :

Answer 14

No plastics to be disposed of anywhere.

Dunnage, incinerator Ash, bottles, synthetic ropes, cooking oil, crockery. All prohibited.

Animal carcass prohibited unless 50nm and 100m depth or if in a special area.

OUTSIDE SPECIAL AREAS.
Ground comminuted food waste of (25mm) maybe disposed of greater than 3 miles from nearest land.

Unground uncominuted food can be disposed of 12 nm from land.

Cleaning agents from water wash of decks and holds permitted anywhere outside of special area.

Cargo residues from deck and hold are permitted at greater than 12nm.

INSIDE SPECIAL AREA.
Everything prohibited except :

Grey water permitted anywhere outside port limits.

Cleaning agents permitted from deck water wash at any distance from land.

Food waste ground and comminuted at greater than 12nm from land.

Cleaning agents from cargo hold water wash permitted at greater than 12nm.

Cargo residues from deck water wash at greater than 12 nm. On condition that there are no reception facilities and two ports of call are within SA.

Cargo residues from hold only on condition if at anchor for a long period of time as long as not directly related to a hold cleaning operation.

Question 15

Annex 2.

IPPC for carriage of NLS.
Certificate of Fitness.

Discharge Criteria for :
Category X and Y (most)

Category Z and OS

Answer 15

X and Y have pre wash requirements or need to be sent ashore to reception facilities.

Y (some) Z and OS if:

1. En route
2. At greater than 7 knots
3. Discharge below the water line.
4. More than 12 nm.
5. More than 25m depth.

Question 16

Free surface effect.

Righting arm/lever

Righting moment

Answer 16

The virtual loss of GM due to movement of a liquid in a partially filled tank when the vessel heels due to external forces, which in effect reduces the GZ (Righting lever) and hence the Righting moment. To counteract this, empty or press up tanks.

When a vessel is heeled by an external force it causes the floating body to right itself until the centre of gravity and buoyancy are in line ie the lever becomes zero. (Aka GZ)

The torque or momentum force which tends to restore a vessel heeled over to its upright position, a product of the Righting arm and the weight of the vessel. This will not happen if there is negative or neutral stability such as a loll.

Question 17

Units of measurement

Nautical Mile

Cable

Anchor chain cable

Answer 17

A nautical mile is based on the circumference of the earth and is equal to one minute of latitude or 1/60th of a degree and is slightly more than a land measured mile.
(1 Nautical Mile = 1852 metres)

A cable length is one tenth of a nautical mile. Or 185.2m

A length of cable from an anchor ⚓ chain 🔗 is 27.4m.

Question 18

Annex 6

Air emissions.

Certification:

1) IAPPC
2) EIAPPC (NOx)
3) IEEDI with management plan for new ships.

Discharge criteria for Air emissions :

Answer 18

1)Ozone depleting substances. (ODS). Prohibited
Unless an old ship which has to use an ozone record book. (ORB)

2) Nitrogen Oxides, (NOxs) Prohibited unless engine is certified to meet prescribed standards. Is engine design compliant or not. EIAPPC for every engine. Require Technical Manual.
3) Sulphur Dioxide, (SOxs) not to exceed 3.5% World wide, or 0.5% from 2020 depending on review and 0.1% in ECA areas. Have to use MCA registered and approved bunker suppliers. And have a sulphur record book, to be kept for 2 years. Use scrubbers.
4) (VOCs) sent ashore by vapour return valve or mixed with cargo. Require Vapour Management Plan.
5) Incinerators must be type approved and certified to meet prescribed standards. Not to be used within port limits.

Question 19

Grain Code Intact Stability Requirements.

The maximum angle of heel due to shift of grain, or angle at which deck edge is immersed, which ever is the lesser.

In a statical stability diagram, the residual area between the heeling arm and the Righting curve up to angle of heel of maximum difference up to 40° or the angle of flooding which ever is least, shall in all conditions of loading be not less than?

Initial Metacentric Height, after correction for free surface effects of liquids in tanks shall not be less than?

Before loading, the master shall, if required by the authority of the port, be able to demonstrate?

And that after loading, the master shall ensure?

Answer 19

The angle of heel due to shift of grain cargo shall not be greater than 12° or the angle of deck edge immersion, whichever is the lesser.

The net residual area upto an angle of heel of 40° or the angle of flooding which ever is least shall not be less than 0.075mr.

The initial GM after free surface correction of tanks shall be not less than 0.30m.

Before loading bulk grain, the master shall demonstrate the ability of the ship at all stages of the voyage to comply with the stability criteria of the grain rules.

After loading the master shall ensure that the ship is upright with even keel before proceeding to sea.

Question 20

Timber Deck Stability criteria.

Initial GM

GM throughout voyage

Max GZ

Angle of max GZ upto 40° in mr

Answer 20

Initial GM in the departure condition should not be less than 0.10m

At all times during the voyage the GM should be positive after free surface correction including absorbtion of of water by deck cargo and exposed surfaces and ice accretion.

Max GZ should be at least 0.25m

Angle of max GZ under the Righting lever at 40° should not be less than 0.08mr