Equipment Number

Anchor weight is determined by a Classification Society formula that throws up a number which we call as Equipment number.

The Equipment number is the trigger to decide the anchor weight the chain size and the length of cable to be used.

The equipment number, EN, on which the requirements of equipment are based is to be calculated as follows:-
EN = K * ENc
where,
ENc = Δ^2/3 + 2BH + 0.1*A

ENc is the function of the ship displacement, Deck height, Area of the superstructure.

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 deckhouse, 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 upper deck, or from a 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.

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