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ICLL 1966 / 1988 Protocol · SOLAS Ch. II-1 (MSC.216(82) & MSC.474(102)) · Freeboard & FWA/DWA

Load Line Survey, Weathertight & Watertight Integrity Checklist (ICLL & SOLAS II-1)

Weathertight and watertight integrity under the International Convention on Load Lines, 1966 / 1988 Protocol (ICLL) and SOLAS Chapter II-1 (IMO Resolutions MSC.216(82) & MSC.474(102)) is a top-5 deficiency category across the Paris MoU, Tokyo MOU, Indian Ocean MOU, and USCG Port State Control regimes.

Complementing our Ship Squat, UKC & Stability Guide and Draft Survey Calculator Guide, this guide provides a complete deck-by-deck walkaround checklist for Plimsoll & seasonal Load Line marks (`TF, F, T, S, W, WNA`), FWA/DWA density allowances, air pipe float heads (`Reg. 20`), hatch covers & weathertight doors, and SOLAS II-1 power-operated sliding watertight doors.

Updated · Written by SeaReady in our own words. Not affiliated with OCIMF, RightShip, CDI, any MoU or any administration — always check the current official documents.

1. Load Line Marks, Freeboard & Closing Appliances (ICLL 1966 / 1988 Protocol)

Every annual Load Line survey (`ICLL Article 14(1)(c)`) and Port State Control deck walk inspects the ship’s Conditions of Assignment of Freeboard (`ICLL Regulations 10–25`):

International Convention on Load Lines 1966 / 1988 Protocol (ICLL) deck closing appliances and freeboard marks.
ICLL Item & RegulationStatutory SpecificationPre-Arrival Deck Inspection & PSC Trap
Load Line Marks, Deck Line & Draught Marks (ICLL 1966/1988 Regs. 4–9)300 mm outer ring diameter; 25 mm line thickness; permanently cut/welded & paintedVerify that the Deck Line (300 mm × 25 mm), Plimsoll Ring (300 mm outer diameter intersected by a 450 mm × 25 mm horizontal line), Classification Society initials (e.g., LR, DNV, ABS, BV, NK), and seasonal load lines (TF, F, T, S, W, WNA) match the International Load Line Certificate millimetre-for-millimetre.
Weathertight Doors & Access Openings in Superstructures (ICLL Reg. 12)Steel construction; operable from both sides; gasket & all dogs/clips free and tightInspect rubber gaskets for paint contamination, cracking, or permanent set; grease all dogs, hinges, and toggles; run a chalk test or hose test (≥ 2 bar from 1.5 m distance); never tie open or remove clips from a superstructure weathertight door.
Cargo Hatch Covers, Coamings, Cleats & Drains (ICLL Regs. 14–16)Rubber packing compression ≤ design limit; non-return drain valves free; cleats snugCheck side/cross-joint rubber packing channels, compression bars, quick-acting cleats, wedges, hydraulic cylinders/chains, and coaming non-return drain valves. On bulk carriers, verify ultrasonic or hose weathertightness test logs and forward hatch-cover operational tests (2011 ESP Code § 3.3.2).
Air Pipes (Tank Vent Heads) & Ventilators (ICLL Regs. 19 & 20)Automatic float/ball closing device; intact corrosion-resistant flame screen; ≥ 760 mm heightAir pipe heads (ballast, fuel, and void tanks) are the #1 Load Line PSC detention item worldwide. Open and inspect float balls/discs, rubber seats, and wire-mesh flame screens; replace corroded coamings or missing clamping bolts; mark every vent and ventilator damper clearly with the space served and OPEN/SHUT indicators.
Sounding Pipes, Scuppers, Freeing Ports & Guardrails (ICLL Regs. 20, 22, 24 & 25)Weighted self-closing cocks on oil tanks; freeing port flaps free (non-locking); 1.0 m guardrailsNever tie open or block a self-closing sounding pipe cock in the engine room or double-bottom tunnel (immediate PSC Code 30 detention). Ensure bulwark freeing-port shutters swing freely on bronze/stainless pins without locking bolts, and keep guardrails (≥ 1.0 m height, ≤ 230 mm lowest course gap, ≤ 380 mm upper courses) intact.

2. Seasonal Load Line Zones, FWA/DWA & Zone-Transition Burn-Off Math

  • Seasonal Load Line Marks (`ICLL Reg. 6`): Relative to the Summer (`S`) load line (whose upper edge passes through the centre of the Plimsoll ring), the Tropical (`T`) mark is 1/48 of summer draught (`T_S`) above `S`; the Winter (`W`) mark is 1/48 × T_S below `S`; the Winter North Atlantic (`WNA`) mark (for ships `≤ 100 m` length) is `50 mm` below `W`; the Fresh Water (`F`) mark is FWA = Δ / (4 × TPC) (mm) above `S`; and the Tropical Fresh (`TF`) mark is `FWA` above `T`.
  • Dock Water Allowance (`DWA`) Verification: Before loading above the salt-water mark in a river or estuary port, sample dock water at midships at half-draught using a clean bucket and calibrated hydrometer, log the observed density (ρ_dock), and compute DWA (mm) = FWA × (1.025 − ρ_dock) / 0.025.
  • Zone Boundary Fuel Burn-Off Calculation: When sailing from a Tropical or Summer zone into a more restrictive zone (e.g., Summer to Winter), calculate the steaming distance and days to the seasonal boundary, multiply by daily fuel/fresh-water consumption (minus water generated), and verify that the ship’s displacement at the boundary will not exceed the Winter deadweight limit.

3. SOLAS Chapter II-1 Watertight Doors, Bilge Alarms & Subdivision Integrity

Below the freeboard/bulkhead deck, internal watertight subdivision is governed by SOLAS Chapter II-1 (IMO Resolutions MSC.216(82) & MSC.474(102)) and the 2009 Code on Alerts and Indicators (IMO Res. A.1021(26)):

SOLAS Chapter II-1 subdivision watertight doors, closing alarms, and weekly operational drills.
SOLAS II-1 SystemPerformance & Timing StandardMandatory Testing & Logbook Evidence
Power-Operated Sliding Watertight Doors (SOLAS II-1/13, 13-1 & 15 / MSC.474(102))Close in 20–40 s upright; local & bridge control; 3 independent stored-energy closuresMust close both locally (from both sides of the bulkhead) and remotely from the navigation bridge in ≥ 20 s and ≤ 40 s with the ship upright, and up to 15° list either way. Hydraulic accumulators must store enough energy for at least 3 complete closures without main power, with low-hydraulic-level, low-gas-pressure, and power-failure alarms (IMO Res. A.1021(26)).
Audible Closing Alarm & Visual Bridge Indicator (SOLAS II-1/13.7.1.6 & A.1021(26) § 3.2.4.2)Distinctive audible alarm sounds before and during remote closure; Red/Green bridge panelClassified as an Emergency Alarm under IMO Res. A.1021(26) § 3.2.4.2. Whenever closed remotely from the central bridge console, the audible alarm must sound before the door begins to move and continue until completely closed, accompanied by an intermittent visual signal in high-noise spaces.
Weekly Drills, Pre-Departure Checks & Official Log Book Entries (SOLAS II-1/21 & 22)Weekly drill of all watertight doors, mechanisms & valves; daily check if used at seaEvery watertight door, sidescuttle, valve, and closing mechanism must be operated weekly (and inspected daily when used at sea in passenger ships), with every opening/closing before departure and during the voyage recorded in the Official Log Book / Deck Log Book.
Bulk Carrier Cargo Hold Water Ingress Alarms & Dewatering (SOLAS XII/12 & XII/13)Two-stage hold water level detectors (0.5 m pre-alarm; 2.0 m / 15% depth main alarm) & forward dewateringUnder SOLAS XII/12 (and 2011 ESP Code §§ 2.8 & 3.7), bulk carriers must have audible and visual bridge alarms for each cargo hold: a pre-alarm at ≥ 0.5 m above the inner bottom and a main alarm at ≤ 15% of hold depth or 2.0 m (whichever is less), plus aft-end ballast/dry space alarms. Under SOLAS XII/13, forward ballast tanks and dry spaces forward of the collision bulkhead must have remote dewatering arrangements controllable from the navigation bridge or propulsion control station.

Run FWA/DWA and stability calculations offline in the SeaReady FWA/DWA Calculator, complete your pre-arrival watertight closure walk in Checklists, and verify Load Line survey readiness in the PSC and Flag & Class guides.

Questions seafarers ask

Why are air pipe automatic closing heads (ICLL Regulation 20) the top Load Line PSC detention item?

Under Regulation 20 of the International Convention on Load Lines 1966 (as modified by the 1988 Protocol) and IMO Resolution A.1206(34) Appendix 2, exposed air pipes serving ballast, fuel, and void tanks are the primary barrier preventing progressive downflooding if the freeboard deck is swept by green seas. If a PSCO finds a wasted air pipe gooseneck, a holed float ball, a missing rubber sealing ring, a float jammed open with wire or paint, or a corroded flame screen on a fuel tank vent, the tank loses reserve buoyancy and weathertight integrity — resulting in an immediate Action Code 30 detention.

How do you calculate Fresh Water Allowance (FWA) and Dock Water Allowance (DWA) for Load Line compliance?

Under the International Load Line Certificate, the Fresh Water Allowance in millimetres is FWA = Δ / (4 × TPC), where Δ is the summer displacement in tonnes and TPC is tonnes per centimetre immersion at summer load draught. When loading in brackish dock or river water of density ρ_dock (between 1.000 t/m³ fresh water and 1.025 t/m³ salt water), the vessel may submerge its applicable seasonal Load Line mark by the Dock Water Allowance: DWA (mm) = FWA × (1.025 − ρ_dock) / 0.025, provided the density is measured by a calibrated hydrometer at the ship’s midships draught and logged in the Deck Log Book.

When may a ship load to the Tropical (T) or Summer (S) Load Line if crossing into a Winter (W) zone during the voyage?

Under ICLL Annex II (Zones, Areas and Seasonal Periods), a ship must never be submerged below the applicable seasonal load line mark at any point along its route. If a ship loads in a Summer (S) or Tropical (T) zone and will enter a Winter (W) seasonal zone during the voyage, the departure draught must be restricted so that the fuel, lubricating oil, and fresh water consumed between departure and the boundary of the Winter zone brings the ship up to or above the Winter (W) mark before crossing the boundary line.

What are the SOLAS Chapter II-1 rules for keeping watertight doors closed at sea?

Under SOLAS regulation II-1/22 (as amended by IMO Resolution MSC.216(82) and MSC.474(102)), all watertight doors in subdivision bulkheads shall be kept closed during navigation, except that doors may be opened during navigation to permit the passage of passengers or crew, or when work in the immediate vicinity of the door necessitates it being opened. The door must be immediately closed when transit through the door is complete or when the task is finished, and the sill/groove must be kept completely clear of cables, hoses, or wooden wedges.

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