Conditions of Assignment of Freeboard

1. Construction, Stability & Superstructure End Bulkheads

A. The Construction of the Ship:

• The construction must be such that her general structural strength will be sufficient for the freeboards to be assigned.
• The design and construction must be such that her stability in all probable loading conditions is sufficient for the freeboards assigned; the stability criteria are given in the Convention.

B. Superstructure End Bulkheads:

• The heights of the sills of openings at the ends of enclosed superstructures should be at least 380 mm above the deck.

What "conditions of assignment" means. Before a Load Line/freeboard can be assigned, the ship must meet a set of construction and closing-appliance conditions that ensure the hull can keep water out — openings raised, closed, or drained. These are the Conditions of Assignment of Freeboard.

2. Hatchways, Machinery Openings, Ventilators & Air Pipes

C. Hatchways Closed by Portable Covers with Tarpaulins:

• Coamings of substantial construction, height above deck at least 600 mm on exposed freeboard and RQD and on exposed superstructure decks within ¼ of the ship's length from the FP, and at least 450 mm on exposed superstructure decks outside ¼ L from the FP.
• Width of bearing surface for the covers at least 65 mm.
• Wood covers at least 60 mm thick with a span not more than 1.5 m; for mild steel portable covers the strength is calculated with assumed loads.

D. Hatchways Closed by Weathertight Steel Covers:

• Coaming heights are as for portable beam covers; this height may be reduced or omitted if the Administration is satisfied that safety is not impaired.
• Mild steel cover strength is calculated assuming the loads given; the product of the maximum stress and the factor 4.25 should not exceed the minimum ultimate strength of the material, and deflections are limited to not more than 0.0028 times the span.
• Mild steel top plating not less than 1% of the stiffener spacing or 6 mm, whichever is greater.

E. Machinery Space Openings:

• Properly framed and efficiently enclosed by steel casings of ample strength; where casings are not protected by other structures their strength is specially considered. Steel access doors with sills at least 600 mm above the deck.

F. Ventilators:

• Steel coamings; where they exceed 900 mm in height they should be specially supported.
• Coaming heights: 900 mm above the freeboard deck and 760 mm above superstructure decks.
• Vent openings provided with efficient weathertight closing appliances, except where coamings exceed 4.5 m (freeboard deck) or 2.3 m (superstructure deck).

G. Air Pipes:

• Exposed parts of substantial construction.
• Height at least 760 mm on the freeboard deck and 450 mm on superstructure decks; a lower height may be approved if these heights interfere with working arrangements.
• Permanently attached means of closing the pipe openings must be provided.

3. Cargo Ports, Scuppers & Side Scuttles

H. Cargo Ports and Similar Side Openings Below the Freeboard Deck:

• Fitted with watertight doors to ensure the ship's structural integrity.
• Unless permitted by the Administration, the lower edge of such openings should not be below a line drawn parallel to the freeboard deck at side, having at its lowest point the upper edge of the uppermost load line.

I. Scuppers, Inlets and Discharges:

• Discharges led through the shell (from spaces below the freeboard deck, or from within superstructures/deckhouses on the freeboard deck fitted with weathertight doors) must have efficient and accessible means of preventing water from passing inboard.
• Normally an automatic non-return valve with means of closing above the freeboard deck.
• Where the vertical distance from the summer waterline to the inboard end of the discharge pipe exceeds 0.02L, the discharge may have two automatic non-return valves without positive means of closing (inboard valve always accessible).
• Where the distance exceeds 0.02L, a single automatic non-return valve without positive means of closing may be accepted (per the Convention wording).
• In manned machinery spaces, main and auxiliary sea inlets/discharges connected with machinery operation may be controlled locally.
• Scuppers and discharge pipes penetrating the shell either more than 450 mm below the freeboard deck or less than 600 mm above the summer waterline must be fitted with an automatic non-return valve.
• Scuppers from superstructures/deckhouses not fitted with weathertight doors should be led overboard.

J. Side Scuttles Below the Freeboard Deck or Within Enclosed Superstructures:

• Fitted with efficient hinged, watertight inside deadlights.
• No side scuttle fitted with its sill below a line parallel to the freeboard deck having its lowest point 2.5% of the ship's breadth above the summer waterline, or 500 mm, whichever is greater.

4. Freeing Ports & Protection of Crew

K. Freeing Ports:

• The minimum freeing port area on each side of the ship, where sheer in way of the well is standard or greater, is given (in square metres) by:
  • A = 0.7 + 0.035l where l is the length of bulwark in the well and is less than 20 m; and
  • A = 0.07l where l is greater than 20 m.
• In no case need l be greater than 0.7L.
• If the bulwark is greater than 1.2 m in height, A is increased by 0.004 m²/m of well length for each 0.1 m difference in height.
• If the bulwark is less than 0.9 m in height, A is reduced by 0.004 m²/m for each 0.1 m difference in height.
• Where there is no sheer, A is increased by 50%; with less than standard sheer the percentage increase is obtained by interpolation.
• The lower edges of freeing ports should be as near the deck as practicable, and two-thirds of the area is required in the half of the well nearest the lowest point of the sheer curve.
• Openings in the bulwarks are protected by bars spaced approximately 230 mm apart; shutters must be prevented from jamming.

L. Protection of Crew:

• Efficient guard rails or bulwarks of minimum height 1 metre on all exposed parts of freeboard and superstructure decks.
• A lower rail may be permitted by the Administration.
• Maximum vertical spacing: 230 mm between deck and lower rail, and 380 mm between other rails.
• Satisfactory means of protecting crew getting to and from their quarters and other parts used in working the ship.

Surveyor asks: "What are the Conditions of Assignment of Freeboard?" Give the headings A–L: construction, superstructure end bulkheads, hatchways, machinery openings, ventilators, air pipes, cargo ports, scuppers, side scuttles, freeing ports and protection of crew — with the key numbers (380 mm sill, 600/450 mm hatch, 900/760 mm vent, 760/450 mm air pipe, 2.5% B side scuttle, 1 m rails).