ship construction and maintenance

Keel: 龍骨

Center line of bottom

Backbone of ship

Commonest form of keel is flat plate keel

First structure that is built is keel

SOLAS said date of keel laid is date of built (birthday of ship)

Small ship use bar keel

Double bottom:

如果隻船太輕載, propeller會露出水面, 以前的船用沙或石頭去ballast.

現今在船底加double bottom. 入水到double bottom去ballast

Double bottom 用了一個cellular system, 即是分開一格格.

Increase ship’s immersion and seaworthiness and stability.

Strength of ship increased, increase safety of human life at sea

除了入水, 也可以  store feed water, fresh water, fuel oil for engines, oil fuel for boiler, lubricating oil.  

裡面果層叫inner bottom or tank top, 出面果層叫bottom shell.

Bottom shell damaged, 只有 double bottom space flooded.

Inner bottom is watertight to bilges/margin plates. Inner bottom由中間去到邊邊都要watertight.

Depth of double bottom depends on center girder, depend on classification society’s requirement. CS對center girder 有minimum height要求

In machinery spaces the double bottom depth increased for store fuel oil, lubricating oil.

在船頭船尾depth of double bottom may be increased for trimming purposes.

Increase in height is gradual, no sudden discontinuities.

Double bottom 要有framing longitudinally or transversely. Ship’s length 長過120m 用longitudinal framing.

Center girder extends whole length the double bottom from fore to aft.

Center girder is water tight,

Center girder的底是keel, 頂是center strake of inner bottom.成一個工字

Floor is vertical transverse plate. 將double bottom分隔成一間間.

Watertight or oiltight floor:

At ends of double bottom, under main bulkheads.

Closing any holes. 密封的

Solid plate floor:

Strengthen bottom transversely.

Support inner bottom.

Have manholes for access through the tanks.

Small air and drain holes.

Bracket floor:

Short transverse plate

Between solid plate floor

Vertical stiffeners attached to solid plate floor. To strength the floor

If ship’s breadth exceeds 10m but not 20m, one intercostal side girder at port and starboard

Exceed 20m, two.

Pounding :

船頭撞落浪, severe stress

Driven into head seas.

特別是lightly ballasted

要加強船頭framing.

Bilge:有3個意思

1 污水

2 倉底

3 damaged and flooded

Transverse bulkheads:

將船分隔成一格格

Provide subdivision

Functions:

Contain flooding

Strengthen hull, resist transverse deformation of ship. Carry vertical loading.

Barrier to fire

Bulkhead的數量由classification societies決定

船頭collision bulkhead

 船尾aft peak bulkhead

Either end of machinery space 要有watertight bulkheads

最少要有4個watertight bulkheads.  

如果machinery space在船尾,aft peak bulkhead two-in-one function. 可以只用3個bulkheads.

Collision bulkhead/ fore peak bulkhead

放在船頭, 當撞船發生, bow is damaged, 防止flooding.

所以collision bulkhead不會放太前, 廢事撞船時撞壞埋bulkhead.

也不會太後.防止flooding時入太多水

Aft peak bulkhead

防止flooding時trim by stern

Propeller有時意外撞穿船尾.

Aft peak bulkhead 放後一點, 船尾撞穿時不要入太多水.

Plating in aft peak bulkhead is doubled or thickened. Resist vibration.

Machinery bulkheads:

Forward and aft boundary of machinery space.

Prevent damage to engines and boilers which are important

Localize fire originating in these space..

Bulkhead高度要到uppermost continuous deck.

Bulkhead的底連接strakes.

Bulkhead上有stiffeners strengthen, 或者用凹凹凸凸的bulkhead叫corrugated bulkhead.

Test watertight bulkheads:

Cargo hold used in ballast 要裝滿水試

其他bulkheads裝水to load waterline.

Classification society是一個組織

Marine classification是它的一個系統

Marine classification is a system for promoting the safety of life, property and the environment primarily through the establishment and verification of compliance with technical and engineering standards for:

·         The design;

·         Construction;

·         Life-cycle maintenance

of ships, offshore units and other marine-related facilities.

Design:

Submit design to classification society.

The design should comply with society rules, which harmonized with international conventions.

每個國家的classification society有各自的rules, 但都跟國際法例沒衝突

Construction:

Classification society surveyor check building in conformance with approved drawings and relevant rules.

Maintenance.

Five-year cycle survey.

Annual, intermediate 2.5年and special surveys 5年

如果合乎requirements就叫remain in class

Damage:

當有嚴重damage. Rules of CS might be breached

要進行 damage survey

如果不合格,要repair to remain in class. 否則不能出船

The International Association of Classification Societies (IACS) [Reference]

IACS is a technically-based organization consisting of thirteen marine classification societies headquartered in London. IACS provides a forum within which the member societies discuss, research and adopt technical criteria that enhance maritime safety.

Whilst there are reported to be more than 50 ship classification organizations worldwide the 13 major classification societies that claim to class some 94% of all commercial tonnage involved in international trade worldwide are members of the International Association of Classification Societies (IACS).

Lloyds Register (LR)

Great Britain

Length overall (LOA):

Length of vessel taken over all extremities.

Forward perpendicular (FP):

A perpendicular drawn to the waterline at the point where foreside of the stem meets the summer load line

Stem is the very most forward part of a ship’s bow and is an extension of the keel.

After perpendicular (AP):

A perpendicular drawn to the waterline at the point where the center line of the rudder stock meets the summer load line.

塊版的中間

Length between perpendiculars (LBP)

Length between FP and AP measured along summer load line.

Amidships:

A point midway between AP and FP

Breadth overall (BOA):

Maximum beam taken over all extremities.

Maximum depth:

From upper deck to lowest point of keel.

Maximum draft:

From lowest point of keel to summer load line.

Base line:

A horizontal line drawn at the top of the keel plate.

Moulded depth:

From base line to summer load line.

Moulded draft:

From base line to upper deck.

量度depth and draft at ship’s side amidships.

Freeboard:

Vertical distance between summer load line and freeboard deck.

Freeboard deck is the uppermost complete deck exposed to weather and sea.

Freeboard deck has permanent means of closing all openings. All openings are watertight.

Sheer:

Curvature of decks in longitudinal direction.

Measured as the height of deck at side at any point above the height of deck at side amidships.

船頭船尾的deck比船中間的deck高.

Sheer adds buoyancy to the ends where it is needed during pitching.

Camber / round of beam:

Curvature of decks in transverse direction.

Measured as the height of deck at center above the height of deck at side

船側的deck比船中間的deck低

Purpose of camber is to ensure a good drainage of water and to strengthen the upper deck.

Rise of floor / deadrise:

Rise of bottom shell plating line above the base line.

船底的側面比船底的中間高.

Purpose is to allow drainage of double bottom water/oil to the center line suction.

Bow flare:

The outward curvature of side shell of bow above waterline.

It promotes dryness and gives additional buoyance.

Prevent the bow from diving too deeply into the water when pitching.

Anchors are clear when lowered from bow flare.

Gross tonnage (GT):

It is a unitless index.

It is calculated based on the moulded volume of all enclosed spaces of ship.

It is used to determine a ship’s manning regulations, safety rules, registration fees and port dues.

GT沒有單位, 是根據船的總volume去計算.

GT關乎船的大小, 用來決定人手需要, 安全規則, 註冊費和碼頭費

Net tonnage (NT):

Dimensionless index. 即係冇單位.

Calculated from moulded volume of ship’s cargo spaces.

Used to calculate port duties and should not be taken as less than 30 per cent of ship’s GT.

NT根據船的cargo space volume來計算

用來計算碼頭稅.

GT 和NT 都沒有單位,根據volume計算

Displacement 和 deadweight tonnage 單位是tonnes, 根據重量/mass

A ship’s displacement is the weight of water that a ship displaces when it is floating with its fuel tanks filled, stores and cargoes, if any aboard

Displacement is the actual weight of the ship.

Displacement = lightweight/lightship + deadweight

Lightweight is the weight of vessel as built.

Deadweight/ deadweight tonnage is the weight a ship is carrying or can safely carry.

IMO international maritime organization

IMO is a specialized agency of United Nations (UN).

Headquarter in London.

Objectives:

Improve maritime safety

Prevent marine pollution.

Work of IMO is conducted through five committees.

1.      The Maritime Safety Committee (MSC) deals with technical work of IMO such as fire protection, ship design and equipment…

2.      The Marine Environmental Protection Committee (MEPC) prevents pollution from ships.

IMO concludes international conventions or agreements.