Port Restrictions in Ship Chartering: Draft, Airdraft, LOA, NAABSA, and Canal Limits

Port Restrictions

Port restrictions are among the most important practical issues in ship chartering, voyage planning, cargo intake calculation, and safe berth nomination. A ship may be commercially suitable for a cargo, but still unsuitable for a particular port, berth, river passage, canal, lock, bridge, terminal, or loading/discharging facility. For that reason, port restrictions must be checked carefully before a fixture is concluded and again before the ship approaches the nominated port.

In dry bulk chartering, port restrictions are not limited to water depth. They may include LOA (Length Overall), beam, arrival draft, sailing draft, airdraft, tide windows, bar draft, lock dimensions, berth length, turning basin diameter, cargo gear outreach, shore crane limitations, mooring arrangements, seasonal closures, ice restrictions, daylight navigation rules, pilotage requirements, political restrictions, war risk areas, trade union action, and local port regulations. A failure to examine these matters may lead to delay, reduced cargo intake, lighterage, deviation, cancellation disputes, unsafe port allegations, demurrage disputes, or loss of a fixture.

Port restriction information is usually exchanged during chartering negotiations through abbreviations and short technical expressions. Shipbrokers, Shipowners, Charterers, operators, port agents, and cargo interests must therefore understand the meaning of these expressions and must not treat them as routine wording. Even a small difference in draft, airdraft, or beam may determine whether the ship can safely enter, load, discharge, or sail.

LOA (Length Overall) Restrictions

LOA (Length Overall) means the total length of the ship from the foremost point to the aftermost point. Ports and berths may impose LOA restrictions because of berth length, river bends, turning circles, lock chambers, mooring layout, bridge openings, or the physical arrangement of the terminal.

A ship may have sufficient draft for a port but still be unable to enter because the ship is too long to swing safely, berth alongside, or pass through a river channel. River ports with winding approaches may be particularly sensitive to LOA. Some berths also have strict maximum length limits because the mooring dolphins, shore loaders, gangways, fenders, or cargo equipment were designed for ships within a particular size range.

When LOA is material, Shipowners should provide accurate ship particulars, including the registered LOA, length between perpendiculars where requested, distance from bow to manifold or hatch positions where relevant, and any protruding structures that may affect safe berthing. Charterers should not nominate a berth unless the ship can safely reach, berth, work cargo, and depart within the port’s physical limits.

Beam Restrictions

Beam is the width of the ship. Beam restrictions become critical when a ship must pass through a lock, narrow channel, canal, bridge opening, dock entrance, or berth pocket. Beam can also affect whether shore cargo equipment can reach the hatch openings properly.

In bulk shipping, beam restrictions are not only navigational. A terminal may ask for the distance from the ship’s rail to the hatch coaming, hatch length and breadth, hatch spacing, outreach requirements, and crane working radius. If a ship is too wide, a shore grab, conveyor, shiploader, or unloader may not reach all parts of the cargo hold. This can create trimming problems, slow cargo operations, or require additional equipment.

Beam also matters in canals and locks because the ship must have sufficient clearance on each side for safe transit. In restricted waterways, port authorities may impose additional requirements for tugs, pilots, mooring lines, daylight transit, weather limits, or special maneuvering arrangements.

Draft Restrictions

Draft is the vertical distance between the waterline and the lowest part of the ship below the water. Draft restrictions are among the most common and commercially important port limits because they directly affect cargo intake, loading plans, discharge plans, and the number of ports a ship can safely serve.

Draft restrictions may apply at the berth, approach channel, river passage, outer bar, lock, turning basin, anchorage, or sailing route. A ship may be able to enter a port at one draft but may need to load or discharge only part cargo because of a sailing draft restriction. Similarly, a ship may be able to berth safely at high tide but not at low tide, or may need to wait for a tide window before crossing a bar.

If the charterparty names a specific discharge port without stating a draft restriction, Shipowners normally need to ensure that the nominated ship can comply with the known restrictions of that port. However, where the charterparty gives Charterers a range of ports or berths to nominate, Charterers must nominate a safe port and safe berth that the ship can reach and use safely, taking into account the ship’s arrival draft, sailing draft, cargo quantity, water density, tide, and local restrictions.

SWAD, FWAD, and BWAD

SWAD (Salt Water Arrival Draft) means the maximum arrival draft of a ship in salt water. Many ocean ports express their draft restrictions on a salt water basis because seawater has greater density than freshwater.

FWAD (Fresh Water Arrival Draft) means the maximum arrival draft of a ship in fresh water. River ports and inland ports often use FWAD. Because freshwater is less dense than salt water, a ship will sink deeper in freshwater with the same displacement. Therefore, a ship that is safely within a salt water draft limit may exceed the equivalent fresh water draft if no correction is made.

BWAD (Brackish Water Arrival Draft) means the maximum arrival draft where salt water and fresh water mix, usually in estuaries, river mouths, and tidal river systems. Brackish water density falls between freshwater and salt water. The actual draft may therefore depend on the local specific gravity, tide, river flow, season, and recent rainfall.

For accurate cargo intake calculation, the ship’s hydrostatic data, dock water allowance, freshwater allowance, and actual water density should be considered. A draft restriction is not simply a number; it must be interpreted according to the water density and the port’s measurement basis.

Airdraft Restrictions

Airdraft is the vertical height of the ship above the waterline. Depending on the context, it may refer to the height from the waterline to the highest fixed point of the ship, such as the radar mast, funnel, antenna, crane top, or bridge top. In cargo operations, airdraft may also refer to the height from the waterline to the top of hatch coamings or hatch covers.

Airdraft restrictions arise when a ship must pass under a bridge, overhead cable, conveyor gallery, loading arm, terminal structure, or airport approach path. A ship in ballast may have a higher airdraft than a loaded ship because the ship sits higher in the water. This is why port authorities and terminals may request the ship’s airdraft in ballast, loaded condition, and intermediate condition.

Some radar masts and antenna arrangements may be collapsible or hinged, but this must be confirmed in advance. The fact that a mast can theoretically be lowered does not automatically mean the port will accept the ship. The operation must be safe, practical, documented, and acceptable to the Master, Shipowners, and port authority.

Bar Draft and River Restrictions

Bar draft refers to a draft restriction at a bar, shoal, or shallow area often found at the entrance of a river or port. Bars are commonly formed by sediment accumulation where river flow meets tidal or coastal movement. A ship may need to cross the bar at or near high tide and may be restricted by a narrow time window.

In many river trades, especially grain, coal, minerals, and other bulk cargo movements, ships may load part cargo upriver, then cross a bar, and finally top off at another port or anchorage with deeper water. This practice must be planned carefully because cargo intake, stability, trim, tide, pilotage, and sailing window all interact.

Bar restrictions can also cause disputes if Charterers nominate a port or berth where the ship cannot safely load the contracted quantity. The charterparty should therefore make clear whether the cargo quantity is based on berth draft, bar draft, tide-dependent draft, always afloat requirements, or top-off arrangements.

Always Afloat and NAABSA

Many charterparties assume that the ship must remain Always Afloat (AA) at the loading or discharging berth. Under an always afloat obligation, the berth should have sufficient water for the ship to remain afloat throughout cargo operations, allowing for tide, draft, trim, and under-keel clearance.

Some ports and berths cannot offer always afloat conditions. In such places, the parties may agree to NAABSA, meaning Not Always Afloat But Safely Aground. Under NAABSA arrangements, the ship may intentionally or customarily rest on the bottom at certain states of tide, provided the ground is safe and the practice is customary for ships of similar size and construction.

NAABSA should never be treated casually. The bottom condition, seabed composition, slope, obstructions, previous experience with similar ships, local custom, hull structure, class requirements, P&I guidance, and Master’s approval all matter. A safe NAABSA berth is not simply a shallow berth; it must be a berth where the ship can lie aground without damage.

Tidal Restrictions and Tide Windows

Tides play a major role in port access and berth safety. The gravitational influence of the moon and sun creates tidal changes that affect available water depth. During Spring Tides, tidal ranges are larger because the forces of the moon and sun act together. During Neap Tides, tidal ranges are smaller because those forces partly counteract each other.

In tidal ports, a ship may only be able to enter, sail, cross a bar, berth, or shift during a limited tide window. If the ship misses that window, the ship may wait for the next suitable tide. This can affect laytime, demurrage, cancellation dates, Notice of Readiness, pilotage planning, and cargo delivery schedules.

Tide predictions are therefore essential for port planning. However, predicted tides may be affected by wind, atmospheric pressure, river flow, storm surge, swell, and local hydrological conditions. For this reason, port agents and pilots should provide updated local guidance before arrival.

St. Lawrence Seaway Restrictions

The St. Lawrence Seaway is one of the most important inland waterway systems in world shipping, connecting the Atlantic Ocean with the Great Lakes. Although the Great Lakes themselves are deep and commercially significant, access to the system is restricted by canals, locks, channels, bridge clearances, seasonal conditions, and environmental requirements.

The Seaway’s lock dimensions and navigation limits create a practical ship size category often called Seawaymax. Ships trading into the Great Lakes must be checked not only for length, beam, draft, and airdraft, but also for mooring arrangements, fairleads, lighting, sewage systems, pollution prevention requirements, and winter navigation limitations.

Because of ice and winter closure, the St. Lawrence Seaway also has a seasonal trading pattern. Shipowners and Charterers planning Great Lakes business must consider opening and closing dates, weather delays, draft restrictions, pilotage, port congestion, cargo readiness, and the risk of missing the navigation season.

Panama Canal Restrictions

The Panama Canal is a central route for world shipping because it connects the Atlantic and Pacific Oceans and avoids the long voyage around South America. Panama Canal restrictions affect ship design, routing, cargo intake, voyage economics, and charterparty negotiations.

The original Panama Canal locks created the familiar Panamax ship size concept. After the canal expansion, larger ships known as New Panamax or NeoPanamax ships became able to transit through the expanded locks. The relevant restrictions include length, beam, tropical fresh water draft, height, equipment, booking rules, water level, and transit availability.

Panama Canal draft is especially sensitive because canal operations depend on freshwater availability in Gatun Lake. During drought periods, the Panama Canal Authority may reduce maximum draft or daily transit capacity. During wetter periods, draft limits may be increased. Charterers and Shipowners should therefore check the latest official canal advisories before fixing a ship for a route that depends on Panama Canal transit.

Suez Canal Restrictions

The Suez Canal connects the Mediterranean Sea and the Red Sea and is one of the most important maritime routes between Europe, Asia, the Middle East, and the Indian Ocean. Unlike the Panama Canal, the Suez Canal has no locks because the two seas are broadly at the same level. This has allowed the canal to be widened and deepened over time to accommodate larger ships.

Suez Canal restrictions include draft, beam, convoy organization, ship type, cargo type, navigational safety rules, security requirements, pilotage, tug assistance, and special rules for large ships. Even where a ship’s dimensions are technically acceptable, transit may require special approval, timing, or operational arrangements.

Political and security developments can also affect Suez Canal routing. In some market conditions, Shipowners and Charterers may compare Suez transit with alternative routing via the Cape of Good Hope, considering bunker cost, war risk premium, canal tolls, insurance, time, emissions, and schedule reliability.

Political, Sanctions, and Security Restrictions

Port restrictions are not always physical. A ship may be restricted by political measures, sanctions, boycott rules, trading history, flag, ownership, cargo origin, cargo destination, crew nationality, previous port calls, or security conditions.

Political restrictions can affect whether a ship is allowed to call at a port, pass through a canal, receive bunkers, obtain port services, or discharge cargo. Sanctions regulations may also prevent trade with certain countries, entities, banks, cargoes, ports, or ships. These restrictions can change quickly and must be checked before fixing and before each voyage order.

War risk areas create additional concerns. Shipowners must protect the ship, crew, cargo, and insurers’ position. War risk premiums, additional insurance, crew bonus, routing clauses, deviation rights, and refusal rights may become important. Charterparties should contain clear war risk, sanctions, and trading limits clauses.

Trade Union and Labour Restrictions

Labour disputes can also restrict port access or cargo operations. Trade unions, stevedores, tug crews, pilots, terminal employees, truckers, or railway workers may affect the ability of a ship to berth, load, discharge, shift, or sail.

The International Transport Workers’ Federation (ITF) and local labour organizations may become involved where crew employment terms, wages, working conditions, or union rules are disputed. In some ports, shore labour may refuse to handle a ship, assist berthing, or provide cargo services if a labour dispute exists.

Time Charterers and Voyage Charterers should understand that labour restrictions can affect hire, laytime, demurrage, off-hire, strikes clauses, force majeure clauses, and safe port obligations. Shipowners will often seek to exclude regions or ports where the ship may be blacklisted, delayed, or exposed to industrial action.

Ice, Weather, and Seasonal Restrictions

Seasonal restrictions may be just as important as fixed port dimensions. Ice, monsoons, hurricanes, typhoons, swell, fog, river floods, drought, sandstorms, and seasonal low water can affect port safety and accessibility.

Ice restrictions may require ice-class tonnage, icebreaker assistance, convoy navigation, higher insurance, special routing, or seasonal closure. River ports may experience high-water restrictions, low-water restrictions, current limitations, or changes in bar depth. Coastal ports may be affected by swell conditions that make berthing or cargo operations unsafe.

Before fixing, the parties should ask whether the port is open year-round, whether seasonal restrictions apply, whether additional insurance or equipment is required, and whether local authorities may impose temporary controls.

Port Restrictions and Safe Port Obligations

Port restrictions are closely connected with the concept of a safe port and safe berth. A port may be unsafe for a particular ship if the ship cannot reach it, use it, and depart from it without being exposed to danger that cannot be avoided by ordinary good navigation and seamanship.

In practice, safe port questions often involve draft, under-keel clearance, berth suitability, weather exposure, swell, mooring arrangements, political risk, war risk, ice, tug availability, pilotage, and terminal safety. A port that is safe for one ship may be unsafe for another ship because of differences in length, beam, draft, gear, age, maneuverability, cargo, or class requirements.

Charterers should nominate only ports and berths that are safe and legally accessible for the nominated ship. Shipowners should provide accurate ship particulars and should raise concerns promptly if the nominated port or berth appears unsuitable.

Information Required Before Fixing

Before agreeing a fixture, the following port restriction information should be checked where relevant:

• Maximum LOA: berth, channel, lock, and turning basin limits.
• Maximum beam: lock, canal, berth, and cargo equipment restrictions.
• Maximum draft: arrival draft, sailing draft, berth draft, channel draft, and bar draft.
• Water density: salt water, fresh water, or brackish water basis.
• Airdraft: bridge, cable, loader, airport, and terminal clearance.
• Tide windows: required tide level for arrival, sailing, bar crossing, and shifting.
• Under-keel clearance: port authority and company requirements.
• Berth conditions: always afloat, NAABSA, bottom condition, and local custom.
• Cargo gear compatibility: shore crane outreach, ship crane capacity, grabs, hoppers, conveyors, and hatch access.
• Seasonal issues: ice, weather, swell, low water, high water, and closure periods.
• Legal restrictions: sanctions, flag restrictions, port bans, political exclusions, and war risk.
• Operational services: pilotage, tug availability, line boats, bunkers, fresh water, waste reception, and security requirements.

Port Restrictions in Charterparty Negotiations

Port restrictions should be addressed clearly in the charterparty. If a ship is fixed for a particular named port, the parties should still identify any known limitations that affect cargo quantity, draft, tide, airdraft, canal transit, or berth safety. If Charterers have a range of ports, the nomination clause should be read together with the safe port, safe berth, trading limits, and cargo quantity provisions.

Where the ship may need to call at restricted ports, the charterparty should clarify whether loading is subject to tide, whether top-off is permitted, whether lighterage is allowed, who pays for lighterage, whether NAABSA is acceptable, whether canal transit is included, and whether any special port charges are for Shipowners’ or Charterers’ account.

Ambiguous wording can create expensive disputes. Expressions such as “about,” “safe berth,” “always afloat,” “reachable on arrival,” “suitable berth,” “maximum arrival draft,” and “Charterers’ option” should be used carefully and consistently with the commercial understanding of the fixture.

Commercial Consequences of Port Restrictions

Port restrictions can directly affect freight, hire, laytime, demurrage, despatch, bunker consumption, canal tolls, insurance premiums, cargo quantity, and voyage profitability. A ship that must wait for tide, part-load upriver, top off elsewhere, lighten cargo, or deviate around a canal restriction may incur substantial additional cost.

For Shipowners, port restrictions may increase exposure to delay, grounding, hull damage, cargo claims, unsafe berth disputes, or off-hire arguments. For Charterers, restrictions may reduce cargo intake, increase freight per ton, create sale contract problems, delay cargo delivery, or require alternative port arrangements.

For these reasons, port restrictions should be treated as a commercial risk allocation issue, not merely a navigational detail. Proper investigation before fixing is usually far cheaper than resolving a dispute after the ship has arrived.

Conclusion

Port restrictions are a central part of safe and profitable ship chartering. LOA, beam, draft, airdraft, SWAD, FWAD, BWAD, bar draft, tide windows, NAABSA, canal limits, political restrictions, labour issues, and seasonal conditions all influence whether a ship can lawfully and safely perform a voyage.

Shipowners must provide accurate ship particulars and assess whether the ship can perform the employment ordered. Charterers must nominate safe and suitable ports and berths within the charterparty terms. Shipbrokers and operators should ensure that restrictions are checked early, recorded clearly, and reflected in the fixture recap and charterparty wording.

In modern shipping, where ships are larger, terminals are more specialized, and regulatory risks are higher, careful attention to port restrictions is essential. A well-planned fixture considers not only the cargo and freight rate, but also the physical, legal, seasonal, and operational realities of every port and waterway involved in the voyage.