Ice Navigation Procedures
Non-ice strengthened vessel now frequently trades in the St. Lawrence during the winter months, in part due to:
- Improved icebreaker assistance
- Improved ice observation
- Improved ice advisory service and ice piloting
- Improved ice charts
These factors will also reduce the risk of damage providing that the ship’s command acts in accordance with sound operating practice in relation to:
- speed in ice conditions
- manoeuvring in ice
- Ice convoy procedures
- Ice reports
- Ice navigation routes
- Drift ice & pack ice
The master must consult the relevant Admiralty & Canadian Sailing Direction, the Mariners’ Handbook, the Ice Navigation in Canadian Waters and the Coast Guard Joint Industry Guidelines, in order to be fully briefed on ice navigation and how best to deal with it. However, cold weather poses several problems of its own. The following guidelines may go a long way in guarding against cold weather damage to a vessel and its equipment.
Superstructure icing is a process which depends upon meteorological conditions. Condition of loading, and behaviour of the vessel in stormy weather, as well as on the size and location of superstructure and rigging. The more common cause of ice formation is the deposit of water droplets on the vessel’s structure. These droplets come from spray driven from wave crests and ship-generated spray. Ice formation may also occur in conditions of snowfall, sea fog.(including Arctic sea smoke) a drastic fall in ambient temperature, and from the freezing of raindrops on contact with the vessel’s structure. Ice formation may sometimes be cause or accentuated by water on board and retained on deck.
Vessel icing is a function of the ship’s course relative to the wind and seas and generally is most severe in the following areas: stem, bulwark and bulwark rail, windward side of the superstructure and deckhouses, hawse pipes, anchors, deck gear, forecastle deck and upper deck. Freeing ports, aerials, stays, shrouds, masts, spars, and associated rigging.
Superstructure icing is possible whenever air temperature are –2.2°C or less and wind are 17 knots or more, and when these conditions occur simultaneously. Generally speaking, winds of beaufort force 5 may produce slight icing; wind of force 7, moderate icing; and winds above force 8. Severe icing. Under these conditions, the most intensive ice formation takes place when wind and sea come from ahead. In beam and quartering winds, ice accumulates more quickly on the windward side of the vessel, thus leading to a constant list which is extremely dangerous.
Most of the time icing happen at night since it is dark on deck no one can notice it happening, unless, they lighten up the deck at time to verify the condition of the spray coming on deck.
BALLAST & CARGO CONDITIONS
Bring the vessel down in the water to a draught at which the sea suctions and propeller are well below the level of any ice. Keep ballast tanks slack by 20% in order to have the sounding lines and air vents free of water, open air vents flap and open sounding lines plug, for any water trap in the line to leak back to the tanks.
Restrict the trim (1-2 meters) to avoid the possibility of ice sliding under the vessel and blocking up the sea suctions.
ENGINE ROOM INLETS
Special precautions are required to prevent the blocking of sea inlets by ice. These precautions will vary and will depend on the type of vessel. The required action should be taken well in advance, after consultation with the vessel’s owners.
Although, it would be prudent from a safety point of view to address, in some detail, a suitable system for maintaining a supply of cooling water to the essential machinery of ships operating under these conditions. The following system of circulation provides on possible solution to the problem:
The ship should be provided with at least one sea bay from which pumps supplying cooling water to essential machinery can draw.
The sea bay should:
- be supported with water from a least two sea inlet boxes
- be connected to the sea inlet boxes by pipes, valves and strainers with a cross sectional area equal to the total area of the suctions served by the sea bay
The sea inlet boxes should:
- be fitted on each side of the ship
- be as deeply submerged as possible
- have an area open to the sea of five to six times the total area of the pump suctions served by the sea bay
Diversion valves and piping should be provided at overboard cooling water discharge to permit warm water to be returned to the sea inlet boxes to prevent blockage, IF POSSIBLE
Means must be provided to clear the sea bays if they do become blocked by ice. There are several design features which can ease or eliminate these problems.
COOLING SYSTEM DIAGRAM
FREEZING OF PIPING, VALVES, DECK & FIRE LINE AND TANKS
The fire-fighting system is often exposed to the environment and must be available when required, draining the fire-main system gives the best protection from freezing. The navigators and engineers should be aware of these potential problems and the solutions available to them on their ship.
STEAM DECK MACHINERY AND STEAM PIPING
Turn on deck steam if possible, when the outside temperature drops and approaches freezing point. Set all deck machinery in motion, turning slowly.
TANKER – CARGO HEATING SYSTEMS
Drain and blow through cargo heating inlet lines, coils and exhausts lines to remove all water. If cargo heating is required during the voyage, carry out the following:
- Turn on the cargo heating steam before encountering temperatures near freezing point: Keep the heating on until reaching warmer weather; blow the coil and lines through with air immediately after turning off the steam.
- Install a small diameter line (jumper line) between the supply and return manifolds on the forward tanks to prevent freezing at the exhaust return.
- Test all steam and exhaust valves for tightness to prevent leakage into “dry lines”.
Drain and blow through all pipelines not in use, this includes, but is not limited to:
- Steam smothering (if fitted) foam system
- Portable water filling lines and systems
- Main fire lines and off takes
- Cargo tank venting systems
- Steam end exhaust lines in pump room
- Butterworth tank washing lines (cow lines with offtakes)
- If the pump room cannot be drained on account of cargo requirement, turn on the steam supply
Reduce the flow of outside air into the engine space by closing down the vent fans and throttling the dampers. On a Diesel driven engine, the closing of dampers and a reduction in the ventilation must not allow a higher then normal vacuum to build up inside the engine space.
Recirculation of air in the engine room should be avoided, as this will result in a higher content of aromatics, hydrocarbon and noxious gases. Circulate freshwater systems continuously to eliminate the possibility of freezing.
EMERGENCY GENERATOR FUEL TANK
If the emergency fuel tank is not provided with heaters and the pour and cloud point of the fuel are not known, then maintain the tank at least 90% full to avoid condensation: if the tank is placed on or above the main deck in a ventilated space, add antifreeze to the radiator and jacket system if the diesel generator is not air cooled.
GENERAL COLD WATER PRECAUTION
Change fresh or brackish ballast water with sea water prior to arrival in the cold water zone.
If the sea water temperature falls or is expected to fall below 0ºC (32ºF), all tanks adjacent to the vessel’s shell plating (double bottom tanks) fore/aft peak, deep tanks, etc.) should be reduced to 90% capacity to allow for expansion, if freezing takes place.
Keep all doors closed as much as possible. Keep accommodation and storerooms warm. Use doors to leeward of the wind. Be alert to the possibility of flooding from frozen and burst water pipes. Burst water pipes normally become evident when the vessel returns to warmer waters.
Keep the deck and alleyways as ice free as possible to reduce the danger of slipping. Apply a generous amount of salt to the deck, to prevent ice forming in areas where there is the most traffic.
Avoid carrying bunkers in the deep tank forward, for tanker only. If space permits, shift cargo from the forward wing tanks to the center tanks, at the same time bringing the liquid lever in No. 1 wings slightly below the water level. If leakage occurs from a tank as a result of ice damage, lowering the level will prevent oil pollution. This is because the water head outside will be higher than that inside the tank. This action must be consistent with the recommended stern trim and well within the allowed stress level.
Check that all crewmembers are wearing clothing and shoes that are suitable for the weather. They must have a supply of cold weather clothing, blankets, etc… on board.
ITEMS USEFUL TO CARRY ON BOARD
- Road salt or sand in bags (for deck, etc.)
- Wooden mall (hammer) (de-ice hatches or windlass) if shipboard accretion, due to freezing spray.
- Shovels, snow scrapers, window scrapers.
- Large plastic in roll (heavy gauge) if some doors or windows doesn’t close tightly
- Antifreeze liquid. For life boat motor or emergency generator
- De-icing liquid (Methyl hydrates) or calcium chloride in powder for Sounding lines, ballast air vent.
- Portable heaters 3 phases (if necessary) for bridge.
- Proper clothing for deck crew.
BALLAST ARRANGEMENT AND M/E COOLING SYSTEM
All your ballast water will have to be changed as per Canadian regulations on water ballast.
Believed that the exchange will be done within the Gulf Stream areas, when crossing the Atlantic, this water will remain warm until Cabot Strait and up to 24 hrs after. Therefore, do not slack the tanks before you reach Port Cartier / Sept-Iles range or as directed by the ice pilot.
The main purpose when slacking the ballasts tanks is to keep all air vents tanks free of water to prevent the pipes from freezing.
When you de-ballast your tanks, keep all sounding lines plugs open, so that no water get clog inside (vacuum in), then put all plugs back on afterward.
Put a plastic or canvas around all ballast air vents, to keep warm air inside.
Keep your hatches close until arrival St.Lawrence port, because cold air would freeze your sounding lines and any vents passing inside the cargo holds.
The fwd cargo hold ballasts and sounding lines are always the first one who often cause problems with frost when holds are open.
If you have a cargo hold filled with water, keep it filled until a few hours before destination. We might use this water to assist in main engine cooling, because sea chest may get plug by frazil ice.
Should you stay at anchor for a long period of time, more than two days, then I recommend that you take out your top side tanks or re-circulate the water in the tanks if possible. But if you need to reduce the air draft for loading, then pump in some water in the top side tanks as needed before docking.
The bottom ballast tanks will not get frozen, but in any case, just re-circulate the water by pumping out a few minutes then pump back in same amount.
At the dock and if temperature is more than -5 and wind more than 15 knots then, just open the hatches as needed for loading, keep others hatches close and to keep the hydronic oil warm, just crack open all hatches a meter or so then close back every hour.
Items to deal with before Cabot Strait:
- drain all deck fire lines down to E/R and keep valves open
- drain your wheelhouse windows washing lines
- take your life boats fresh water inside and have your engines started daily or keep warm
- put in your emergency generator cooling system, anti-freeze liquid, keep the room warm. Same for emergency fire pump
- batten down tight the accommodation doors not needed and use one windward door access to main deck
- slack your anchors by 1 meters in case of freezing spray, weather permitting.
Items needed in case ballast sounding lines and air vents get frozen:
- The product used is call de-icing liquid, a product made out of methanol and can be supplied at load port
- Another product also good for this is call calcium chloride and it come in powder pellets bag, which when mixed with water, gives a good result in freeing sounding lines. You can procure these items from your ship chandler at destination.
Next items needed is road salt for the deck alleyways in order to keep ice free the walking areas. Shovels and snow scrapers. Suitable clothing for deck crew who has to perform mooring and loading operations; it is necessary to have suitable clothing to prevent frostbite.