Calculating the Size of the Ship Anchor as per Classification Society

-
The equipment number, EN, on which the requirements of equipment ship anchor are based is to be calculated as follows :-
EN = K * ENc

where,
ENc = Δ^2/3 + 2BH + 0.1A

where,
Δ = moulded displacement, [t], to the summer load water line.
H = effective height, [m], from the summer load waterline to the top of the uppermost deck-house, to be measured as follows:
H = a + Σhi
a = distance [m] from summer load waterline amidships to the upper deck at side.
hi = height [m] on the centreline of each tier of houses having a breadth greater than B/4. For lowest tier, hi is to be measured at centre line from the upper deck, or from the notional deck line where there is a local discontinuity in the uppers deck.
A = area [m2] in profile view of the hull, superstructures and houses above the summer load waterline, which is within the Rule length of the vessel. Houses of breadth less than B/4 are to be disregarded.
In the calculation of H and A, sheer and trim are to be ignored.
Parts of windscreens or bulwarks which are more than 1.5[m] in height are to be regarded as parts of houses when determining H and A. The height of the hatch coamings and that of any deck cargo, such as containers, may be disregarded.

‘K’ is a factor depending upon the type of vessel and service notation as given below: For fishing vessels,
K = 1.00
For other vessels,
K = 1.00 for vessels of Unrestricted Service.
K = 0.85 for vessels of Coastal Service

Having  found  the  equipment  numeral  the  details  regarding  sizes  and  quality   may  be  obtained  from  the  rigging  tables  provided  in  these  regulations. The  equipment  numeral  is  also  given  in  the  class certificate  and  hence  there  is  no  need  to  refer  to  this  formula  to  find  the  equipment  numeral   whenever  there  is a need as  in  the  case  of  ordering  new  chain  lengths  when  old  chain  lengths  have  been  worn  beyond  the  rule  requirement. For  information  and  guidance  a specimen  of  the  Rigging  table  is  reproduced  in next blog.

Comments

Post a Comment

Popular posts from this blog

Introduction to Mooring Line

-
Image
The mooring refers to any permanent structure to which a vessel/ship may be secured. Examples include quays, wharfs, jetties, piers, anchor buoys, and mooring buoys. A ship is secured to a mooring to forestall free movement of the ship on the water. An anchor mooring fixes a vessel's position relative to a point on the bottom of a waterway without connecting the vessel to shore. As a verb, mooring refers to the act of attaching a vessel to a mooring. Mooring is often accomplished using thick ropes called mooring lines or hawsers. The lines are fixed to deck fittings on the vessel at one end and to fittings such as bollards, rings, and cleats on the other end. Mooring requires cooperation between people on a pier and on a vessel. Heavy mooring lines are often passed from larger vessels to people on a mooring by smaller, weighted heaving lines. Once a mooring line is attached to a bollard, it is pulled tight. Large ships generally tighten their mooring lines using heavy machin
Read more

Introduction to Towline

-
Image
A tow line is used with a tug (tugboat or towboat) which is a type of vessel that maneuvers other vessels by pushing or pulling them either by direct contact or by means of a tow line. Tugs typically move vessels that either are restricted in their ability to maneuver on their own, such as ships in a crowded harbor or a narrow canal, or those that cannot move by themselves, such as barges, disabled ships, log rafts, or oil platforms. A tow line is the essential link between tug and ship. This applies to tugs operating alongside a vessel in the push-pull mode as well as to towing tugs fastened with a tow line to the bow or stern of a ship, also called `tugs towing on a line‟. Basic towline requirements A towline must fulfil two basic functions, firstly to function as the load-carrying link between tug and ship and secondly to cope with the dynamic loads resulting from the relative motion between tug and ship. This leads to the following basic requirements for towlines for harbo
Read more

Component of Ship Anchor Windlass

-
Image
The windlass machinery is combined with the forward mooring winch as one unit. The main winch consists of a double reduction gearing arrangement to produce a large torque. A brake is provided for control and a windlass is usually powered by an electric or hydraulic motor operating via a gear train. An ideal windlass assembly consists of a cable lifter, mooring drum and a warp end. All these are rotating equipment that work together for the anchoring process. The cable lifter has cable shaped snugs that are used to grip the anchor cable on the drum. The cable from the cable lifter goes around a mooring drum, which guides the cables by paying out or letting go of the mooring wires. A warp end is used to hold the cable at the desired position and is always driven in association with the mooring drum for efficient carrying out of the warping duties. Although all these units work together, they can also be individually controlled. A dog clutch is used to separately engage or diseng
Read more