Naval Architecture: naval architecture

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Friday, 10 March 2017

Latest Jobs In Goa Shipyard || GOA

Adv Ref No : 02/2017
Grade Name : Kindly refer our detail Advt. 02/2017 and corrigendum
Pay Scale : Kindly refer our detail Advt. 02/2017 and corrigendum
Job Titles :
01 - GENERAL MANAGER (HR and A)
02 - ADDITIONAL GENERAL MANAGER (HR)
03 - ADDITIONAL GENERAL MANAGER (COMPANY SECRETARY)
04 - DEPUTY GENERAL MANAGER (COMPANY SECRETARY)
05 - ADDITIONAL GENERAL MANAGER (FOR TECHNICAL ASSISTANT TO CMD)
06 - DEPUTY GENERAL MANAGER (FOR TECHNICAL ASSISTANT TO CMD)
07 - SENIOR MANAGER (FOR TECHNICAL ASSISTANT TO CMD)
08 - DEPUTY GENERAL MANAGER (PUBLIC RELATIONS)
09 - SENIOR MANAGER (PUBLIC RELATIONS)
10 - MANAGER (PUBLIC RELATIONS)
11 - MANAGER (SAFETY) - (ON FIXED TERM BASIS FOR 3 YEARS)
12 - DEPUTY MANAGER (SAFETY) - (ON FIXED TERM BASIS FOR 3 YEARS)
13 - ASSISTANT MANAGER (HULL) - (ON FIXED TERM BASIS FOR 3 YEARS)
14 - ASSISTANT MANAGER (RESOURCE PLANNING) - (ON FIXED TERM BASIS FOR 3 YEARS)
15 - ASSISTANT MANAGER (MECHANICAL) - (ON FIXED TERM BASIS FOR 3 YEARS)
16 - ASSISTANT MANAGER (ELECTRICAL) - (ON FIXED TERM BASIS FOR 3 YEARS)
17 - ASSISTANT MANAGER (FINANCE) - (ON FIXED TERM BASIS FOR 3 YEARS)
18 - ASSISTANT MANAGER (LEGAL) - (ON FIXED TERM BASIS FOR 3 YEARS)
19 - MANAGEMENT TRAINEE (MECHANICAL)
20 - MANAGEMENT TRAINEE (ELECTRONICS AND COMMUNICATION)
21 - MANAGEMENT TRAINEE (ELECTRICAL)
22 - MANAGEMENT TRAINEE (ELECTRICAL / ELECTRONICS)
23 - MANAGEMENT TRAINEE (NAVAL ARCHITECTURE)
Job Overview :
Kindly refer our detail Advt. 02/2017 and corrigendum
How to apply :
Kindly refer our detail Advt. 02/2017 and corrigendum
Click here for Advertisement Details

ASSISTANT MANAGER (HULL) || Goa Shipyard

Adv Ref No : 02/2017
Post ID : 02/2017/13
Job Title : ASSISTANT MANAGER (HULL) - (ON FIXED TERM BASIS FOR 3 YEARS)
Grade Name : E1
Pay Scale : 16400-3%-40500
Job Overview :
Essential Educational Qualification: Candidates should have Bachelor of Engineering (B.E.) / Bachelor of Technology (B. Tech.) in Naval Architecture from a recognized University / Institution with minimum First class or 60% marks or equivalent CGPA.
Other Information :
Essential Educational Qualification: Ex- Navy/ CG, retired as MCPO or equivalent grade. Desirable Qualification: Any advanced / additional Diploma / Certificate Course from a recognized University / AICTE approved institution in Manufacturing Technology / Production Engineering. Essential Work Experience: Hands on experience of minimum 10 years in hull systems, deck equipment, LSA/ FFA etc. In case of Govt./PSU minimum 01 year in the pay scale of ? 12600-3%-32500/- (IDA). Desirable Experience: Relevant managerial work experience in Hull Outfit areas like Fitting / alignment / welding etc., in ships/submarines production industry.
How to apply :
Kindly refer our detail Advt. 02/2017 and corrigendum
Click here for Advertisement Details

MANAGEMENT TRAINEE (NAVAL ARCHITECTURE) || Goa Shipyard

Adv Ref No : 02/2017
Post ID : 02/2017/23
Job Title : MANAGEMENT TRAINEE (NAVAL ARCHITECTURE)
Grade Name : E1
Pay Scale : 16400-3%-40500
Job Overview :
Essential Educational Qualification: Candidates should have Bachelor of Engineering (B.E.) / Bachelor of Technology (B. Tech.) in Naval Architecture from a recognized University / Institution with minimum First class or 60% marks or equivalent CGPA.
Other Information :
CONDITIONS FOR MANAGEMENT TRAINEE POSTS:
Candidates studying the Final Year may also be considered for training, provided they get at least 60% or more (aggregate marks till the Last semester) as decided by the Management. However before joining the Company they should complete their final year in 1st class. Candidates will be short listed for calling for written test based on their performance/result/grading/ percentage as declared by the respective University. The selected candidate will undergo “On the Job training” for a period of one year which may be extended if necessary. During the training period the candidate will be paid a basic pay of ? 16,400/- per month in the pay scale of ? 16400-3%-40500 (E-1 grade) plus other allowances / benefits as applicable to Management Trainees in accordance with the GSL policy. On satisfactory completion of training, based on the company’s requirement and depending upon the performance during the training period, they may be considered for absorption as Assistant Manager in the E-1 grade carrying pay scale of ? 16400-3%-40500 or its equivalent as revised from time to time on Fixed Term Employment basis for a period of 3 years which can be further extended upto another two years or as per the Fixed Term Employment policy in vogue. On satisfactory completion of the training and on absorption in the Assistant Manager grade on fixed term employment, they will be given one increment in the scale. All Management Trainees considered for absorption as Assistant Manager will be on probation for a period of one year from the date of absorption as Assistant Manager. The period of 01 year as Management Trainee (or extended period as Management Trainee) will not be counted as service and for other consequential service benefits.
Education Requirment :
Candidates should have Bachelor of Engineering (B.E.) / Bachelor of Technology (B. Tech.) in Naval Architecture from a recognized University / Institution with minimum First class or 60% marks or equivalent CGPA.
How to apply :
Kindly refer our detail Advt. 02/2017 and corrigendum

Click here for Advertisement Details

Friday, 20 January 2017

Topic - 11 Damage stability (Stability in the damaged condition)

Damage stability calculations are much more complicated than intact stability. Software utilizing numerical methods is typically employed because the areas and volumes can quickly become tedious and long to compute using other methods.

The loss of stability from flooding may be due in part to the free surface effect. Water accumulating in the hull usually drains to the bilges, lowering the centre of gravity and actually decreasing (It should read as increasing, since water will add as a bottom weight thereby increasing GM) the Meta centric height. This assumes the ship remains stationary and upright. However, once the ship is inclined to any degree (a wave strikes it for example), the fluid in the bilge moves to the low side. This results in a list.

Ø Floodable Length: The floodable length at any point within the length of the ship is the maximum portion of the length, having its center at the point which can be symmetrically flooded at the prescribed permeability, without immersing the margin line.

Floodable length (in short) is the length of (part of) the ship that could be flooded without loss of the ship.

Ø Determination of Floodable length is essential to determine

How many watertight compartments (bulkheads) are needed
Factor of subdivision (How many water compartments flooded without loss of ship)

Thursday, 19 January 2017

Topic - 12 Stability systems

The stability systems are classified as
1.1.1 Passive systems

1.      Bilge keel: A bilge keel is a long fin of metal, often in a "V" shape, welded along the length of the ship at the turn of the bilge. Bilge keels are employed in pairs (one for each side of the ship). A ship may have more than one bilge keel per side, but this is rare. Bilge keels increase the hydrodynamic resistance when a vessel rolls, thus limiting the amount of roll a vessel has to endure.

2.      Outriggers: Outriggers may be employed on certain vessels to reduce rolling. Rolling is reduced either by the force required to submerge buoyant floats or by hydrodynamic foils.

3.      Antiroll tanks: Antiroll Tanks are tanks within the vessel fitted with baffles intended to slow the rate of water transfer from the port side of the tank to the starboard side. The tank is designed such that a larger amount of water is trapped on the higher side of the vessel. This is intended to have an effect completely opposite to that of the free surface effect.

4.      Para vanes: Para vanes may be employed by slow-moving vessels (such as fishing vessels) to reduce roll.

1.1.2        Active systems

Active stability systems are defined by the need to input energy to the system in the form of a pump, hydraulic piston, or electric actuator. These systems include stabilizer fins attached to the side of the vessel or tanks in which fluid is pumped around to counteract the motion of the vessel.
1. Stabilizer fins: Active fin stabilizers are normally used to reduce the roll that a vessel experiences while underway or, more recently, while at rest. The fins extend beyond the hull of the vessel below the waterline and alter their angle of attack depending upon heel angle and rate-of-roll of the vessel.
2. Gyroscopic internal stabilizers: Gyroscopes were used to control a ship's roll. Gyro stabilizers consist of a spinning flywheel and gyroscopic precession that imposes boat-righting torque on the hull structure. A gyroscope has three axes: a spin axis, an input axis, and an output axis. The spin axis is the axis about which the flywheel is spinning and is vertical for a boat gyro. The input axis is the axis about which input torques is applied. The principal output axis is the transverse (athwart ship) axis about which the gyro rotates in reaction to an input.

Wednesday, 18 January 2017

Topic- 13 Stability Considerations

1. Crane Outreach

When using cranes and other lifting gear such as A frames that are barge mounted, it must be noted that the weight of the lifted load acts at the point of suspension – not at the base of the crane. The overturning moment on the barge, tending to cause it to capsize, is the product of the weight of the lifted load, and the (horizontal) distance of the point of suspension from the centre of buoyancy.

The greatest uplift or detachment force, acts at the point of attachment (of the crane to the barge) furthest from the point of suspension. This is the force tending to turn the crane over and the moment of this force is the product of the weight of the lifted load, and the (horizontal) distance of the point of suspension from the point of uplift.

2. Free surface effect

Fluids such as fuel and water can adversely affect the stability of a moving vessel. A shallow covering of water over a large enclosed deck can cause a significant problem. 150 mm of fresh water covering a 24 m by 6 m deck weighs 21.6 tonne, and as the vessel rolls this weight will be transferred outboard to the down side of the roll. Sloshing is another phenomenon, which can greatly amplify the destabilizing effect of a large free surface of fluid. The effect of sloshing is worst if the movement of fluid coincides with the movement of the vessel. Baffles are used to break up the free surface within a tank and to prevent sloshing.

3. Shifting Cargo

Securing arrangements should be of such design that they are strong enough to prevent any cargo movement during transit. Maritime Rule part 24B gives prescribed requirements for stowage and securing of all cargoes.

4. Loading and Discharge

It is vital that stability is considered during all phases of barge operations, including loading and discharge. The stability conditions during loading and discharge are often quite different from those when fully loaded. High loads, moving loads, and off–centerline loading plans all need special consideration. A low initial GM value, a combined KG that is close to or below the required minimum and small righting areas all mean that the loaded barge will have poor recovery characteristics when rolling in a seaway.

Tuesday, 17 January 2017

Topic - 14 SCANTLINGS

Purpose

This document summarizes the scantling sizing calculations for the hull structure of the subject vessel. The subject vessel is an 80 m x 34 m x 9 m (molded) unmanned barge intended for ocean service.

Procedure

Hull scantling calculations are based on the requirements of the American Bureau of Shipping (ABS) Rules for Building and Classing Steel Barges, 2014.

Introduction

The amidships scantlings as specified in the Rules are to apply throughout the midship 0.4L. End scantlings are not to extend for more than 0.1L from each end of the barge. The reduction from the midship to the end scantlings is to be affected in as gradual a manner as practicable. Sections having appropriate section moduli or areas, in accordance with their functions in the structure as stiffeners, columns or combinations of both, are to be adopted, due regard being given to the thickness of all parts of the sections to provide a proper margin for corrosion. It may be required that calculations be submitted in support of resistance to buckling for any part of the barge’s structure.

Dimensions

Definitions:

To inner shell surfaces

L (LOA) molded - shell throws outboard

L (scantling) 96% of waterline length at 85% of D

B (breadth) molded - shell throws outboard

D (depth) molded - amidships at side

d (draught) molded - to summer load line

Tuesday, 28 July 2015

STRUCTURAL PARTS OF THE HULL

The hull is the main body of the ship below the main outside deck. The hull consists of an outside covering (or skin) and an inside framework to which the skin is secured. The skin and framework are usually made of steel and secured by welding. However, there may still be some areas where rivets are used. The steel skin may also be called shell plating.

The main centerline structural part of the hull is the keel, which runs from the stem at the bow to the sternpost at the stern. The keel is the backbone of the ship. To the keel are fastened the frames, which run athwartship. These are the ribs of the ship and gives shape and strength to the hull. Deck beams and bulkheads support the decks and gives added strength to resist the pressure of the water on the sides of the hull.

SKIN

The skin, or shell plating, provides water-tightness. The plates, the principal strength members of a ship, have various thickness. The heaviest plates are put on amidships. The others are put on so that they taper toward both ends of the ship (from the keel toward the bilge and from the bilge toward the upper row of plates). Using plates of various thickness reduces the weight of the metal used and gives the vessel additional strength at its broadest part. The plates, put on in rows from bow to stern, are called strakes. They are lettered consecutively, beginning at the keel and going upward.

STRAKE NAMES

The bottom row of strakes on either side of the keel, are called garboard strakes. The strakes at the turn of the hull, running in the bilge, are bilge strakes. The strakes running between the garboard and bilge strakes are called bottom strakes and the topmost strakes of the hull are sheer strakes. The upper edge of the sheer strake is the gunwale.

BULKHEADS

The interior of the ship is divided by the bulkheads and decks into watertight compartments. A vessel could be made virtually unsinkable if it were divided into enough small compartments. However, too many compartments would interfere with the arrangement of mechanical equipment and the operation of the ship. Engine rooms must be large enough to accommodate bulky machinery. Cargo spaces must be large enough to hold large equipment and containers.

ENGINE ROOM

The engine room is a separate compartment containing the propulsion machinery of the vessel. Depending on the size and type of propulsion machinery, other vessel machinery may be located there (such as generators, pumping systems, evaporators, and condensers for making fresh water). The propulsion unit for vessels is a main engine. The "shaft" or rod that transmits power from the engine to the propeller leads from the aft end of the engine to the propeller.

EXTERNAL PARTS OF THE HULL

The waterline is the water-level line on the hull when afloat. The vertical distance from the waterline to the edge of the lowest outside deck is called the freeboard. The vertical distance from the waterline to the bottom of the keel is called the draft. The waterline, draft, and freeboard will change with the weight of the cargo and provisions carried by the ship. The draft of the ship is measured in feet and inches. Numbered scales are painted on the side of the ship at the bow and stern.
The relationship between the drafts at the bow and stern is the trim. When a ship is properly balanced fore and aft, she is in trim. When a ship is drawing more water forward than aft, she is down by the head. If the stern is too far down in the water, she is down by the stern. If the vessel is out of balance laterally or athwartship (leaning to one side) she has a list. She may be listing to starboard or listing to port. Both trim and list can be adjusted by shifting the weight of the cargo or transferring the ship’s fuel and water from one tank to another in various parts of the hull.
The part of the bow structure above the waterline is the prow. The general area in the forward part of the ship is the forecastle. Along the edges of the weather deck from bow to stern are removable stanchions and light wire ropes, called life lines. Extensions of the shell plating above the deck are called bulwarks. The small drains on the deck are scuppers. The uppermost deck running from the bow to the stern is called the weather deck. The main deck area over the stern is called the fantail or poop deck. The flat part of the bottom of the ship is called the bilge. The curved section where the bottom meets the side is called the turn of the bilge.
Below the waterline are the propellers or screws which drive the ship through the water. The propellers are attached to and are turned by the propeller shafts. A ship with only one propeller is called a single-screw ship. Ships with two propellers are called twin-screw ships. On some ships (especially landing craft) there may be metal frames built around the propellers (called propeller guards) to protect them from damage. The rudder is used to steer the ship.

NAMES OF DECKS

The decks aboard ship are the same as the floors in a house. The main deck is the first continuous watertight deck that runs from the bow to the stern. In many instances, the weather deck and the main deck may be one and the same. Any partial deck above the main deck is named according to its location on the ship. At the bow it is called a forecastle deck, amidships it is an upper deck, and at the stern it is called the poop deck. The term weather deck includes all parts of the forecastle, main, upper, and poop decks exposed to the weather. Any structure built above the weather deck is called superstructure.

SHIPBOARD DIRECTIONS AND LOCATIONS

Bow

The front end of the ship is the bow. When you move toward the bow, you are going forward, when the vessel is moving forward, it is going ahead. When facing toward the bow, the front-right side is the starboard bow and the front-left side is the port bow.

Amidships (Center)

The central or middle area of a ship is amidships. The right center side is the starboard beam and the left center side is the port beam.

Stern (Back)

The rear of a vessel is the stern. When you move in that direction you are going aft, when the ship moves in that direction it is going astern. When looking forward, the right-rear section is called the starboard quarter and the left-rear section is called the port quarter.

Other Terms of Location and Direction

The entire right side of a vessel from bow to stern is the starboard side and the left side is the port side. A line, or anything else, running parallel to the longitudinal axis or centerline of the vessel is said to be fore and aft and its counterpart, running from side to side, is athwartships.

From the centerline of the ship toward either port or starboard side is outboard and from either side toward the centerline is inboard. However, there is a variation in the use of outboard and inboard when a ship is on berth (moored to a pier). The side against the pier is referred to as being inboard; the side away from the pier as outboard.

STERN ARRANGEMENT

THE UPPER PART OF THE STERN OF A SHIP EXTENDS ABAFT THE RUDDER POST, & THERE MUST BE A SPECIAL ARRANGEMENT OF FRAMING TO SUPPORT IT.
THIS FRAMING IS MAINLY CARRIED BY THE ‘TRANSOM’, WHICH CONSISTS OF A DEEP, HEAVY FLOOR, SECURELY ATTACHED TO THE RUDDER POST, IN ASSOCIATION WITH A TRANSVERSE FRAME & BEAM. THESE ARE KNOWN AS THE ‘TRANSOM FLOOR’ & ‘TRANSVERSE BEAM’.
THE TRANSOM FLOOR MUST HAVE THE SAME DEPTH AS THE FLOORS IN THE CELLULAR DB, BUT MUST BE SLIGHTLY THICKER.

ORDINARY STERNS:

THESE WERE OFTEN CALLED ‘COUNTER’, OR ‘ELLIPTICAL’ STERNS.
INSTEAD OF THEM, CRUISER OR TRANSOM STERNS ARE USED.

CRUISER STERNS:

THEY HAVEA SYSTEM OF ORDINARY TRANSVERSE FRAMING WHICH IS SUPPORTED BY AN INTERCOASTAL GIRDER AT THE CENTRE LINE.
THE GIRDER HAS TO BE DOUBLED, JUST ABAFT THE TRANSOM FLOOR, TO ALLOW THE RUDDER STOCK TO PASS.
A NUMBER OF CANT FRAMES ARE FITTED ABAFT THE AFTERMOST TRANSVERSE FRAME.
THE FRAMES ARE TO BE OF THE SAME SIZE AS BULB ANGLE FRAMES IN PEAKS & ARE TO EXTEND TO THE STRENGTH DECK.
THE FRAME SPACING IS NOT TO EXCEED 610 mm.
WHERE EXTRA STRENGTH IS REQUIRED, WEB FRAMES MAY BE REQUIRED & ALSO EXTRA LONGITUDINAL GIRDERS TO SUPPORT THEM.

TRANSOM STERN:

THIS IS SIMILAR TO A CRUISER STERN, EXCEPT THAT THE CANT FRAMING AT THE AFTER END IS OMMITED & IS REPLACED BY A FLAT PLATE, CALLED A TRANSOM.

RUDDER TRUNK

THIS IS OFTEN FORMED BY CARRYING -UP THE DOUBLED CENTRE GIRDER TO THE DECK ABOVE IN THE FORM OF A BOX.

BEAMS & FRAMES

BEAMS

Usually of offset bulb or inverted angle section, placed athwart ships.

Deck beams are required to support the deck & any loads it carries
Deck beams act as struts assisting in holding the sides of the ship apart against the inward pressure of the sea.

FRAMES

Usually of offset bulb or inverted angle section, placed on side shell.

Scantlings of transverse frames increase with depth & spacing.
Transverse frames may be numbered from aft to for’d.
Frames are required to support the shell plating

TYPES OF FRAMES

TRANSVERSE FRAMES
LONGITUDINAL FRAMES
WEB FRAMES

BULKHEADS

Vertical partitions in a ship arranged transversely are referred to as bulkheads.
The bulkheads subdivide the ship into a no. of watertight compartments.
They give large structural support, resist any tendency to deformation (racking stresses) & assist in spreading the hull stresses over a large area.
All ships are to have a Collision bulkhead, situated <0.05L & >0.08L for cargo ships (.05L + 3 m for passenger ships).
All ships are to have an after peak bulkhead enclosing the stern tube in a w-t compartment.
All ships are to have a bulkhead at each end of the machinery space.
Additional w-t bulkheads are to be fitted in cargo ships depending on the length of the ship.

SHIPBOARD MEASUREMENTS

A ship’s size and capacity can be described in two ways--linear dimensions or tonnages. Each is completely different yet interrelated.

A ship’s measurement is expressed in feet and inches--linear dimensions. A ship is a three dimensional structure having length, width, and depth.

A Ship’s Dimensions

Draft - The depth of a ship in the water. This vertical distance is measured from the bottom of the ship to the surface of the water. Draft marks are cut into or welded on the surface of a ship’s plating. They are placed forward and aft on both sides of the hull and also amidships. At the midships draft we will also find the authorized Load Line markings which designate maximum drafts allowed for vessels under various conditions.

Freeboard - The vertical distance from the water line to the top of the weather deck on the side.

FREEBOARD

Freeboard is the distance between the waterline and the freeboard deck at mid length. The freeboard deck is the uppermost continuous deck which has means of closing all openings. Rules allow different freeboards for different ships in relation to their construction and cargo they carry. There are two types of ship;

Type A -which covers vessels designed to carry only liquid cargoes.

Type B-Which covers all other types of ship,

For type A ships cargo tanks must only have small openings which can be effectively sealed

Type B ships must have sufficient bulkheads and sealing arrangements for openings, but such openings e.g. hatches can be large

The freeboard allowed will be smaller for the type A ship compared to the type B ship of similar length because of the type of cargo carried and means of access for water. Type B ships classed as B-60 may have their freeboard reduced by 60% of that required for a normal B-100 ship provided that its method of construction approaches that of the type A ship. This type exists with OBO's.

Monday, 27 July 2015

TONNAGE MEASUREMENT

GROSS TONNAGE:

IT IS A MEASURE OF SHIP’S CUBIC CAPACITY
IT IS EXPRESSED IN TERMS OF 1 TON/100 CU FT., OR 1 TON/3M³ OF SPACE
GRT CONSISTS OF ALL ENCLOSED SPACES WITH CERTAIN EXCLUSIONS

GRT IS MADE OF SUM OF FOLLOWING:

TOTAL VOLUME BELOW TONNAGE DECK
CU. CAPACITY OF ALL SPACES IN T.D.
CU. CAPACITY OF ALL ENCLOSED SPACES ON OR ABOVE UPPER DECK WITH CERTAIN EXCEPTIONS
EXCESS HATCHWAYS IN EXCESS OF ½ % OF SUM OF a+b+c ABOVE

EXCLUDED SPACES

TANKS USED EXCLUSIVELY FOR BALLAST.
SPACES USED EXCLUSIVELY FOR MACHINARY SPACES FOR CREW & OFFICERS.
WASHING & SANITARY SPACES FOR CREW & OFFICERS
SPACES USED FOR NAVIGATION, RADIO ROOM, STORAGE FOR BATTERIES, CHAIN LOCKER

The gross tonnage (GT) of a ship shall be determined by the following formula:

GT = K₁*V

Where: V = Total volume of all enclosed spaces of the ship in cubic meters,

K₁ = 0.2 + 0.02 log ₁₀V

NET TONNAGE:

IT IS FOUND BY MAKING DEDUCTIONS FROM GRT
IT MAY BE DESCRIBED AS MEASURE OF EARNING CAPACITY OF THE SHIP
ALLOWANCE IS MADE FOR PROPELLING POWER
MASTER’S & CREW’S ACCOMMODATION INCLUDING WASH ROOM
WATER BALLAST SPACES OTHER THAN DOUBLE BOTTOM TANKS
SPACES USED FOR NAVIGATION, RADIO ROOM, & STORAGE SPACE FOR BATTERIES & SAFETY EQUIPMENT
CHAIN LOCKER
WHEN CARGO IS CARRIED BY FOREIGN GOING SHIPS IT IS MEASURED AND ADDED TO NRT

The net tonnage (NT) of a ship shall be determined by the following formula:

NT = K₂ * Vc * (4d / 3D) 2 + K₃ * [N₁ + N₂ / 10]

Vc = total volume of cargo spaces in cubic metres,

K₂ = 0.2 + 0.02 log ₁₀V

K₃ = 1.25

D = moulded depth amidships in metres

d = moulded draught amidships in metres

N₁ = number of passengers in cabins with not more than 8 berths,

N₂ = number of other passengers,

K2 * Vc * (4d / 3D) 2 Shall not be taken less than 0.25GT

NT Shall not be taken less than 0.30GT

VENTILATORS, AIR AND SOUNDING PIPES

Ventilators are necessary to give adequate air circulation to under deck spaces, accommodation and tanks. The coamings of ventilators are to have a minimum height above the weather deck of 900 mm in Position 1 and 760 mm in Position 2 Where the coamings exceed 900 mm in height they are to be specially stayed.

All ventilators are to be provided with means of closing unless the height of the coaming exceeds 4.5 m in Position 1 and 2.3 m in Position 2.

Special care is to be taken when designing and positioning ventilator openings, particularly in regions of high stress concentration.

Mushroom, gooseneck and other minor ventilators are to be strongly constructed and efficiently secured to the deck.

Goose or swan neck type ventilators are mainly used for air pipes to tanks. The height (H) shown is not to be less than 760 mm on the freeboard deck and 450 mm on the superstructure deck. Air pipes are to be fitted at the opposite end of the tank to that at which the filling pipe is placed and/or at the highest point of the tank.

Sounding pipes are to be as straight as possible and to have a bore not less than 32 mm. Where a sounding pipe passes through a refrigerated compartment where temperatures may be 0°C or below the bore is not to be less than 65 mm. Striking plates of adequate thickness and size are to be ﬁtted under open-ended sounding pipes.

AIR PIPES

Every tank on board ship must be provided with an air pipe; the purpose of providing an air pipe is to expel air from the tank during liquid filling operation and inlet air during liquid pump out operations. In other words, air pipes provide a passage way for inlet and expulsion of air during liquid movement, thus preventing Vacuum being formed in the tank.

The bore of the air pipe will much depend upon the volume of the tank to which it is fitted.

Every air pipe fitted to Double Bottom and deep tank which extends upto the shipside or any tank which may run up by the sea is always led above the Bulkhead (weather) deck.

Every air pipe leading from fuel tanks, cargo oil tanks, cofferdam having its opening above the weather deck must be of such height, where no danger will result from leakage of oil or its vapour.

The open end of the air pipes must be provided with closing arrangement, be fitted with weather tight closing arrangements, ball valve in the trunk of the pipe and spark arrester mesh on

the mouth of the air pipe, as required by the load line conditions assignment.

All exposed air pipes shall be of substantial construction, its height above the deck must be at the minimum 760 mm. in position - 1 and minimum 450 mm. In position 2; as far as possible, air pipes must be located in lee of the hatch / bulwark or such place where it has minimum exposure to damage.

BILGE WELL AND SUCTION ARRANGEMENTS

BILGE WELL IS A COMPARTMENT FITTED WITH SUCTION ARRANGEMENTS TO PUMP OUT ANY LIQUID THAT MAY FIND ITS WAY INTO THE CARGO COMPARTMENT.
BILGE WELL PROJECTS IN TUHEDOUBLE BOTTOM TANK, WITH ITS .0PENING FLUSHED TO THE TANK TOP, THE MARGIN PLATES MUST BE WATER TIGHT
BILGE IS DIVIDED INTO TWDCOMPAARTMENTS, THE FILTER BAY AND THE SUCTION BAY.
SUCTION BAY FIATTED WITH A STRUM BOX, THE SIDE WALLS OF THE STRUM BOX MUST BE PERFORATED, ATLEAAST 0NE SIDE MUST HAVE SLIDING OR HINGE OPENING ACCESS FOR INTERNAL CLEANING OF THE STRUM BOX.
SUCTION LINE MUST BE FITTED WITH A NON – RETURN VALVE.
SUCTIOAN LINE MUST NOT BE. LESS THAN 50 mm. INTERNAL DIAMETER.
EACH PERFORATION MUST BE 1 Cm.

PATENT STEEL HATCH COVERS

Patent steel hatch covers having direct securing arrangements, e.g. MacGregor Steel Hatches are a great improvement on the portable type previously described and are universally fitted for weather decks. They consist of plated covers stiffened by webs or stiffeners, watertightness being obtained by gaskets and clamping devices.

Securing cleats and cross joint wedges, together with suitable jointing material are to be fitted, the cleats are to be spaced to ensure weathertightness with a minimum of two per panel at the sides and with one arranged adjacent to each corner at the hatch ends. The cross joint wedges are spaced about 1.5 m apart.

The portable sections of folding covers are connected to one another and can easily and quickly be rolled into or out of position, leaving clear hatchways and decks. The normal practice is for the lengthwise opening of patent hatches but sideways opening hatches are found on some particular types of ships, e.g. OBO carriers, see pages 85 and 125. Patent steel hatch covers may be operated manually or hydraulically. The illustration shows a folding patent steel hatch cover.

The wheels at the sides of the hatch sections, eccentric rollers, are used for raising the hatch section clear of the coaming and for rolling it along the coaming trackway. As shown the axles of these wheels are so adjusted that when the hatch is in the closed position the weight is no longer borne by them. The jointing fits tightly on the coaming and the hatch is made completely weathertight by fitting and securing the cleats.

The roller is used when the hatch cover is pulled into its stowage position. It engages on the plate edge at the ends of the hatchway and the hatch section is turned into the vertical. Wires, chains or bars attached to the stub axles of these rollers at the centre of the wheel enable all the hatch sections to be drawn back and forth together.

The cross joints are made weathertight as shown with cross joint wedges.

Naval Architecture

Monday, 3 April 2017

NA & Ship Co Quiz II

Thursday, 23 March 2017

NA & Ship Co Quiz I