Load Line convention simplified

International Load Line Convention 1966 (ILLC) Simplified.

International LoadLine Convention is a IMO convention adopted on 5^th April 1966 and entered in to force on 21^st July 1968.

Why ILLC? (The Purpose)

The ILLC aims to establish uniform principles and rules with respect to limits which the ships engaged in international voyages may be loaded having regard to safeguarding life and property at sea.

Brief history.

The first LoadLine convention was adopted in 1930 based on the principle of reserve buoyancy. It was also recognised that adaquate freeboard ensures stability and to avoid excessive hull stresses due to overloading.

The ILLC 1966 have taken into account the freeboard by sub division and damage stability conditions.

The Structure of ILLC

The ILLC has 3 annexes. Annex 1 is further divided in to 4 chapters.

		ILLC
Annex 1		Annex 2		Annex 3
1. Chapter 1 - General		1. Zones, areas and seasonal periods		1. Certificates
2. Chapter 2 – Conditions of assignment of freeboard
3. Chapter 3 - Freeboards
4. Chapter 4 – Special requirements for ships assingned timber freeboards

Loadline ammendments that never came into force.

Various ammendments were adopted in years 1971, 1975, 1979 & 1983. They required positive acceptance of two thirds of the parties involved. This has not been reached, therefore never came into force.

So, What is TACIT Ammenndment procedure?

As you have read above, it takes a long time an ammendment to come into force by positive acceptance. In order to speed up this procedure, TACIT ammendment procedure was introduced which was included in 1988 protocol.

How does the tacit ammendment procedure work?

By tacit ammendment procedure an ammendment adopted to the International LoadLine Convention will enter into force 6 months after the deemed date of acceptance unless one third of the parties reject it.

Usually the duration from the date of adoption to date deemed acceptance is 2 years.

What happened to the 1995 ammendments?

The 1995 ammendments was adopted under the possitive acceptance method -did not enter into force were superseeded by 2003 ammendments.

2003 ammendments were adopted in June 2003 entered into force in 01^st Jan 2005.

Lets have a look at the contents of ILLC.

Annex I – Articles

There are 34 articles. A few important points mentioned below,

• Article 2 – Definitions
• Article 4 – Application
  • Applies to all ships engaged in international voyages
• Article 5 – Exemptions
  • 1 a) Ship's of war
  • b) New ships of less than 24 meters / 79 ft in length
  • c) Pleasure yachts not engaed in trade
  • e) Fishing vessels
  • 2 For ships navigating in Great Lakes, Caspian sea, The Plate.
• Ariticle 6- Exemptions
• Article 14- Initial, renewal inspections
• Article19- Duration and validity of certificate
• Article 31- Suspension

Annex I – Chapter 1 (Regulations 1 to 9) - General

Regulation Number	Description	Remarks
1	Strength of the ship
2	Application
3	Defintions of terms used in annexes
4	Deck line	Dimentions of the deck line described. Length = 300mm/ 12 inches, Thickness = 25mm/ 1 inch. Marked amidships on each sides.
5	Load Line mark
6	Lines to be used with Load Line mark
7	Mark of assigning authority
8	Details of marking
9	Verification of marks

Annex I – Chapter 2 (Regulations 10 to 26) – Conditions of assignment of freeboard

Regulation Number	Description	Remarks
10	Information to be supplied to the master
11	Bulkheads
12	Doors
13	Position of hatchways, doorways & ventilators
14	Cargo and otherhatchways
15	Hatchways cloased by portable covers & secured watertight by tarpaulins & batterning devices Hatchway coamings
16	Hatchways closed by watertight covers of steel or other equalant material fitted with gaskets and clamping devices
17	Machnery space openings
18	Misc, openings in freeboard & superstucture decks
19	Ventilators
20	Air Pipes
21	Cargo ports and other similar openings
22	Scuppers, inlets, & discharges
23	Side scuttles
24	Freeing ports
25	Protection of the crew
26	Special conditions of assignments for type 'A' ships.

Annex I – Chapter 3 (Regulations 27 to 40) – Freeboards

Regulation Number	Description	Remarks
27	Type of ships
28	Freeboard tables
29	Correction to the freeboard for ships under 100 mtrs (328 ft) in length
30	Correction for block co-efficient
31	Correction for depth
32	Correction for position of deck line
33	Standard height of superstructure
34	Length of superstructure
35	Effective length of superstructure
36	Trunks
37	Deduction for superstructure & trunks
38	Sheer
39	Minimum bow height
40	Minimum freeboard

Annex I – Chapter 4 (Regulations 41 to 45) – Special requirements for ships assigned timber freeboard.

Regulation Number	Description	Remarks
41	Application of this chapter
42	Definitions
43	Construction of ship
44	Stowage
45	Computaion of freeboard

Annex II – (Regulation 46 to 52) Zones, areas and seasonal periods

Regulation Number	Description	Remarks
46	Nothern winter seasonal zones and area
47	Sothern winter seasonal zone
48	Tropical zone
49	Seasonal tropical areas
50	Summer zones
51	Enclosed areas
52	The winter north atlantic loadline

Annex IV – Certificates

1. International Load Line Cetificate
2. Iternational Load Line Exemption Certificate

Any idea of Mean of Mean of Mean Draught?

The term mean of mean of mean draught is also termed as Quarter mean draught. Commonly used in draught surveying. Lets see how the quarter mean draft is derived.

Consider,
Fwd draught  = Fd
Midship draught = Md
Aft draught = Ad

Mean draught = (Fd +  Ad) / 2

Mean of Mean draught or Half mean draught 
 = (((Fd +  Ad) / 2) + Md)/2 
= (Fd +  Ad + 2Md ) /4

Mean of mean of mean draught or Quarter mean draught 
 =((Fd +  Ad + 2Md ) /4) / 2
= (Fd +  Ad + 6Md) / 8

The mean of mean of mean is the draught that is used to refer the stability booklet or the hydrostatic tables with.

Ship Board Operations - Draft Survey 1

Draft Survey - 1

Introduction

Purpose: The purpose is of a draft survey is to determine the present amount (weight) of the cargo on board, thereby calculating the cargo loaded or discharged.

The formula -  Cargo weight = Present displacement - (Light ship + Ballast + Stores  + Fresh water + Constant)

Objective: Objective is to find the cargo weight presently on board. For that  Light ship, ballast, stores, constant are known. Therefore, finding the present displacement will solve the equation.

The method in brief:

1. Read the drafts at 6 points and correcting them for their respective perpendiculars. 

2. Using the corrected drafts above, obtaining the "Mean of mean of mean draft" or the "Quarter mean draft" (QMD)
3. Refer the hydrostatic table or the ship's stability booklet with the quarter mean draft and obtain the displacement.

4. Calculate the 1st trim correction or "Layer correction" and applying it to the displacement on step 3.

5. Calculate the 2nd trim correction and applying it to the displacement on step 4.

6. Correct the displacement above for sea water. (if the vessel is not floating in sea water)

7. Subtract all known wights onboard including the light ship displacement to get the present cargo weight on board.

Statical stability curve. (GZ curve)

Minimum stability requirements (as to the date)

Having a positive GM value alone is not sufficient.

 The minimum stability criteria for cargo ships as per the Load Line Convention

1. The area under the curve of righting lever (GZ curve) shall be not less than, 
1. 0.055 meter radians up to an angle of 30°
2. 0.09 meter radians up to an angle of 40° or the angle at which lower edges of any openings in the hull,superstructure or deck house which cannot be closed watertight, are immersed if that angle be less
3. 0.03 meter radians between 30° and 40° or the angle referred above

  2. The righting lever (GZ) should be 0.20m at an angle of heel equal to greater than 30°.
  3. The maximum righting lever (GZ) should occur at an angle of heel not less than 30°.
  4. The transverse meta-centric (GM) height should not be less than 0.15m.

IMO recommended general criteria for cargo ships  (IS code 2008)

(The only difference from the Load line rules above is that the maximum righting lever should occur at angle of heel not less than 25°. Others are the same.)

1. The area under the curve of righting lever (GZ curve) shall be not less than, 
1. 0.055 meter radians up to an angle of 30°
2. 0.09 meter radians up to an angle of 40° or the angle of down flooding if that angle be less
3. 0.03 meter radians between 30° and 40° or the angle referred above
   

  2. The righting lever (GZ) should be 0.20m at an angle of heel equal to greater than 30°.
  3. The maximum righting lever (GZ) should occur at an angle of heel not less than 25°. If this is not practicable, an alternative criteria based on an equalant level of safety may be applied to the approval of the administaration.
  4. The transverse meta-centric (GM) height should not be less than 0.15m.

 

 

 

Statical stability curve. (GZ curve)

Introduction

The Statical stability curve or the GZ curve is drawn by plotting the GZ values against the angle of heel. It is drawn for each voyage condition for a particular displacement and KG.

Illustration 1: GZ curve - Source - http://thenauticalsite.com/NauticalNotes/Stability/MyStability-Lesson06-CurvesofStatStab.htm

 Following data can be extracted from a GZ curve,

1. Initial metacentric height (GM). Its the point of intersection when a tangent drawn at the origin and the purpendicular at 57.3° or 1 radian meets. The scale on the GZ shows the value of initial GM.
2. Point of contra fexture. Point of Contra flexture means the point on the curve where the direction of bending. Angle of heel at this point represents the angle of deck edge immersion (DEI).
3. Maximum GZ and the angle of heel it occurs.
4. The range of piositive stability.
5. Angle of of vanishing stabitlity.
6. The moment of stability for a given angle of heel. (GZ x Displacement = FLM)
7. The dynamical stability for a given angle of heel. (Dynamical stability at Ɵ° = Ship's displacement in tonnes (W) x Area between the GZ curve and the baseline upto the angle of heel in im meter-radians. (A))

Navigation - General formulas

General Navigation Formulas. 

Topics Covered:

1. Plane Sailing

2. Parallel Sailing

3. Mercator Sailing

Plane sailing formula can be used generally up to 600 nautical miles, there after mercator sailing should be used. Sums are not presented as these are some basics in navigation.


1. Plane Sailing

N.1 - Plane Sailin

As these are right angles triangles,

Tan Co. = Depature / D.Lat
Sin Co. = Departure / Distance


The formulas above are sufficient to solve any given problem of plane and parallel sailing.

Cos Latitude = Departure / D.Long










2. Parallel Sailing.

The name itself gives the idea. It is sailing parallel on a particular latitude. The course will be due east (090) or due west(270).


The parallel sailing formula is,

• Cos. mean Lat = Dep / D.Long

when sailing parallel mean latitude is referred as Cos Latitude.





3. Mercator Sailing.

N.3 - Mercator Sailing

DMP = Diffence between Meridional Parts. Meridional Parts (MP) can be read from Traverse tables. Difference of Meridional parts can be calculated by either subtracting MPs or adding MPs.

Following fomulas can be derived,

• Tan Co. = DMP / D'Long

• Dep. = D'Long x Cos mean. Lat