6. Operation in Sub-Zero Conditions
6.1 Cold Weather PrecautionsBefore entry into cold weather (when the temperature is expected to fall below zero) the Master should ensure that all personnel are fully aware of the hazards of operating in sub-zero temperatures and of the need to take additional precautions to prevent damage to, or freezing of, equipment.
Deck and engineering officers must ensure that equipment, particularly safety equipment, is regularly checked whilst in cold weather, daily if necessary, to ensure that it remains fit for purpose.
These procedures are primarily designed for vessels which are not specifically equipped for operation in sub-zero temperatures. Ice class vessels should apply and adapt these procedures as necessary to supplement any special equipment fitted.
6.2 Deck and Superstructure Icing
Deck and superstructure icing is a complicated process which depends upon meteorological conditions, the condition of loading and the behaviour of the vessel in bad weather. The most common cause of ice formation is the deposit of water droplets on the vessel's structure and decks. These droplets come from spray driven from wave crests and from ship-generated spray.
Ice formation may also occur in snowfall, sea fog, a sudden fall in ambient temperature, and from the freezing of raindrops which come into contact with the vessel's structure.
Freezing spray warnings are usually included in marine forecasts. However, it is difficult to provide accurate forecasts as to the effects of icing as individual vessel characteristics have markedly different results. Graphs assessing the rate of icing based on air temperature, wind speed, and sea-surface temperature can provide a guide to possible icing conditions, but should not be relied on to accurately predict ice accumulation rates. Caution should be exercised whenever winds of about 17 knots or more are expected, in combination with air temperatures below -20C. Generally speaking, winds of Beaufort Force 5 will produce light icing; winds of Force 7 moderate icing, and winds of 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.
Icing is a function of the ship's course relative to the wind and sea and generally is most severe in the areas of the bow, bulwarks and rails, the windward side of the superstructure and deckhouses, hawse pipes, anchors, deck gear, forecastle and upper decks, freeing ports, aerials, masts and associated rigging.
The effects of freezing spray can be minimised by reducing speed in heavy seas, by running with the sea, or by seeking more sheltered conditions.
It is important to try to maintain the windlass free of ice so that the anchor may be dropped in an emergency.
6.2.1 Severe Icing and the Effect on Stability
Ice accretion on deck can significantly affect stability, although the occasions when this might happen are very few and far between. Ice build up on deck in significant amounts only occurs when the vessel is shipping seas or spray in sub-zero conditions, and whilst in open water.
Obviously the more ice there is on deck, the more the stability is affected.
It is extremely difficult to estimate precisely the amount of ice on deck, but a reasonably accurate figure can be determined by multiplying the deck area coated by an estimated average thickness.
The Master and Chief Officer must be fully aware of the effect of icing on the stability of the vessel, and must have pre-calculated how much may be allowed to accrue on deck before the stability is affected enough to warrant taking preventative action. Under severe icing conditions manual removal of ice becomes important because of the effect on stability.
Such action must be taken well before stability becomes of concern. The manual removal of solid ice is a long and difficult process and the best course of action is to avoid the accretion of ice in the first place. Where there is concern that the amount of ice accumulating on deck might significantly affect stability, measures should be taken to reduce the propagation of it, for example by reducing speed in order to reduce the amount of spray coming on board, or by heading in a different direction. An important factor will obviously be how long the icing conditions are expected to continue for. Whilst in ice bound waters the only ice build-up will be from snow, or possibly rain. This should be relatively easy to remove manually if necessary.
6.2.2 Removal of Ice
The removal of ice on deck should only be attempted when considered absolutely necessary.
Wooden tools are preferred to steel, in order to prevent damage to equipment. The use of steam hoses should be considered, but adequate precautions must obviously be taken to prevent injury to personnel.
Ice removal equipment such as wooden mallets, shovels, crow bars, hammers, spikes and sledge hammers should be readily available in various locations. Steam or hot water hoses should be available.
An adequate supply of sand and salt for decks should be arranged and should be stored in readily available locations, particularly forward and around the accommodation decks. It is important that walkways are maintained safe for personnel as far as is possible.
6.3 Crew Protection
Winter clothes – suitable jackets, gloves, boots, balaclavas etc. must be available for the crew who are expected to work outside. These should have been obtained prior to entering cold areas.
The crew must be briefed on the dangers of exposure to freezing conditions, and the significant effect that wind can have on increasing the chill factor. They should be instructed to ensure that walkways are either kept ice-free or coated in sand or salt.
6.4 Accommodation and Internal Spaces
All external doors to the accommodation, stores, pump room, emergency escapes, emergency generator room, safety equipment stores, and the foc’s’le space should be closed. Vents, where not required for ventilation, should be closed.
The accommodation and critical spaces must be maintained at an adequate temperature for crew comfort and to prevent damage to equipment. If necessary where equipment is liable to damage from freezing conditions, it should be moved to another appropriate location.
Space heaters, where fitted, must be checked as fit for purpose and used as required. These include the bow thruster compartment, foc’s’le space, emergency generator room, emergency fire pump compartment, under deck passages and duct keels, where fitted.
Oil tank heaters must be turned on.
6.5 Navigation Bridge
The following precautions should be taken:
• Ensure bridge window heating is fully operational, and that it remains in use during periods of sub-zero temperatures. If heating is not available transparent heat shrink film may assist in the prevention of frost and condensation. Portable fans or improvised ducting fed from the bridge heating system may also be used, but care must be taken to avoid significant temperature changes which might cause windows to crack;
• Provide equipment such as scrapers, de-icing spray and salt on the bridge;
• Wheelhouse heaters should be kept on. If not fitted, portable heaters should be provided, consistent with safety. It is important that an adequate temperature is maintained in the wheelhouse to protect sensitive electronic equipment;
• The bridge window wash water line should be drained and the drains left open;
• Ensure that the whistle heater, if fitted, is operational and remains on at all times, and that compressed air is moisture free. Drain any water traps;
• Slack down all signal halyards;
• Keep radar scanners running at all times whilst in sub-zero temperatures;
• Ensure that navigation and deck lights remain fit for purpose and ice-free;
• Switches for the duct heaters to be switched on (where fitted).
• Clear-view screens to be kept running when needed;
• Search lights should be checked as fit for purpose;
• Ensure that the EPIRB trace-heating is operational – it should activate automatically by thermostatic control when the temperature drops below –20C.
It is important that there is an effective means to maintain clear vision through the wheelhouse windows. All round vision must remain unimpaired. Any mechanical means to clear moisture from the outside of a window should have an operating mechanism protected from freezing or ice accumulation that could impair its effective operation. Humidity from the heating system should be avoided in order to prevent window fogging.
6.6 Fire, Foam and Deck Lines
Prior to entry into cold weather the fire, foam and fresh water lines must be isolated and drained completely. Drain valve plugs should be left open. The notice CCR5 - Cold Weather Precautions must be displayed on the Bridge and in the Cargo and Engine Control Rooms, stating that the fire lines have been isolated and drain valves plugs are opened. Notices must also be posted at each fire and foam pump operating position.
All exposed valves must be left cracked open because moisture may freeze the valve seat and the valve together rendering the valve impossible to open. It is possible that with some fire line configurations additional drains may need to be fitted to allow adequate draining.
Using fire lines in below freezing temperatures, or maintaining water in the line, requires a constant flow of water through all exposed lines and branches. This is achieved by opening end valves slightly and leading water overboard through hoses, although care should be taken to avoid branch lines becoming water full and freezing.
After using a fire line in freezing conditions it must be quickly drained, within 10 minutes, and again all exposed valves left cracked open. Use of the anchor cable washing should only be considered if there is no possibility of significant ice accumulations in the hawse pipe.
6.7 Holds and Other Spaces
Holds and bilges in all areas liable to freezing should be stripped dry. The chain locker and foc’s’le spaces should also be stripped dry.
Where sounding pipes are exposed, the level in the associated tank should, as far as possible, be lowered to prevent freezing of the sounding pipe and subsequent damage. Where the pipe cannot be drained then consideration should be given to using anti-freeze.
When receiving freshwater alongside, water is to be left running continuously. Ensure that the end of the hose is pushed well down inside the freshwater tank filling pipe to prevent freezing.
6.8 Deck Equipment
Prior to entering into cold weather conditions action must be taken to ensure that all moving equipment, including mooring winches, roller and pedestal leads, cargo lashings, vent flaps, hatches, door hinges and dogs, trackways, sounding pipes, hydrants and valves, ship’s side railing openings, etc. have been adequately lubricated in order to prevent seizure. Antifreeze mixed with the grease has proved to be effective.
• All loose equipment on deck should be stowed away;
• Exposed electric and air motors of accommodation ladders, provision cranes, bunker davits, electric whistle, winch starting switch boxes etc. should be protected with canvas covers;
• Pilot ladders should be kept under cover and protected against icing. Pilot ladders must not be deployed overboard too early in order to prevent them becoming slippery and dangerous;
6.8.1 Cargo Equipment
The following precautions must be taken:
• Steam and condensate lines such as heating coils, IGS pipework and decontamination showers which are not in use, should be drained, blown through if necessary, and the drains left open;
• If cargo heating is required, the following recommendations should be followed: the heating system should be operated before entering cold weather, and should remain on until finally clear;
• Cargo and COW lines should be drained to prevent solidification of the cargo;
• Where fitted, heating of p/v valves should be operational and used as necessary;
• All p/v valves should be regularly checked for correct operation whilst in cold weather;
• Deck cargo heaters and tank cleaning heaters, where fitted, should be drained;
• IGS deck seal heating must be operational as used as necessary;
• IGS p/v breakers must be filled with a suitable glycol/water mixture according to the manufacturer’s instructions.
6.8.2 Mooring Equipment The following precautions must be taken:
• Mooring ropes on drums must be kept covered until required for mooring operations. In severe conditions consideration must be given to removing ropes from drums and storing them internally;
• The windlass and mooring winches should be operated well in advance of mooring operations. In severe conditions hydraulic tank heaters should be turned on. In severe conditions and whilst alongside consideration should be given to keeping mooring winches operating at slow speed;
• Polypropylene and other synthetic ropes are best suited for severe temperature use - manila should not be used for lashings as it becomes stiff and difficult to handle.
When in freezing conditions, decks and walkways should be kept free of ice as far as is possible.
6.8.3 Anchors
Where freezing spray conditions are likely there must be means of clearing ice from the anchor hawse pipes and windlasses before arriving in restricted waters.
When approaching a freezing spray area it is good practice to leave anchors slightly lowered – about 1 metre – in order that the hawse pipe may be cleared by heaving the anchor as well as by lowering it. Care should be taken to avoid damage.
Ice accretion on windlass brakes resulting in loss of grip should also be taken into consideration.
It may be necessary to de-ice brakes before lowering anchors.
6.9 Hydraulic Machinery Rooms The following precautions must be taken:
• Hydraulic systems should be filled with fluid designed for cold weather operation;
• The space heater, where fitted, should be checked for correct operation;
• The oil tank heater should be used as necessary;
• The compartment vent should be closed, or a shield used;
• A small quantity of 70% Isopropyl Alcohol will remove moisture in hydraulic oil and ease control mechanisms, but the equipment manufacturer’s instructions must be reviewed.
6.10 Cold Weather Precautions with Ballast The following precautions must be taken:
• Seawater freezes at about -30C (280F);
• Where fitted, heating should be operated in all wing ballast tanks, even those which are empty. This will prevent condensate freezing and damaging lines;
• All ballast and freshwater tanks should have sufficient ullage to allow for expansion due to freezing. When alongside, if practicable, the level in ballast tanks should be lowered to below the waterline to prevent freezing – ballast water will not freeze below the waterline except in extreme conditions;
• Where sounding pipes are exposed, the level in the associated tank should, as far as possible, be lowered to prevent freezing of the sounding pipe and subsequent damage.
Where the pipe cannot be drained then consideration should be given to using anti-freeze;
• Ballasting and de-ballasting operations must only be carried out after confirming that air-pipes are clear. Operations must be very carefully monitored. It is advisable to strip each tank completely to prevent freezing of any small volumes of water;
• Where fitted, heating should be operated in fresh water tanks, even those which are empty. The temperature of fresh water tanks should be regularly monitored.
6.11 Safety Equipment 6.11.1 Lifeboats
The following precautions must be taken:
• When approaching cold weather, an additive specifically designed to aid the starting of diesel engines should be added to the fuel tank in the proportions recommended by the manufacturer;
• Regular engine oil should be replaced by an appropriate winter grade type such as 5W30.
Synthetic oils reduce friction and can achieve easier starting than multi-grade oil in cold weather. Instruction on the proper viscosity for lubricating oil should be obtained from the lifeboat engine manufacturer’s manual;
• Where fitted, engine heaters should be in use. A suitable temporary heater may be used, consistent with safety. A fire resistant blanket over it may be used to conserve heat.
Electrical cables should not be run through access doors or windows;
• The lifeboat engines must be operated more frequently in cold weather to ensure continued satisfactory operation. The engine starting systems should be able to operate in temperatures of –150C and within two minutes of commencing the start procedure;
• Any water cooling of lifeboat engines must have an adequate amount of antifreeze in the coolant. The antifreeze mixture should prevent freezing up to temperatures of at least – 350C to avoid damage to the cylinder block;
• All lifeboat sea water lines must be drained of water as far as is practicable;
• Precautions should be taken to prevent the freezing and subsequent damage to lifeboat fixed fresh water containers by ensuring that there is sufficient space for expansion should they freeze. Portable water containers can be moved to an internal location and personnel temporarily delegated on the muster list to load the water into the boats in the case of an emergency;
• Equipment in the lifeboats such as the bilge pump and rudder must be regularly checked to ensure that they remain free to move;
• The lifeboat davits, blocks, sheaves, micro-switches, release equipment and all other running gear must be adequately lubricated to ensure continued operation;
• Emulsified oil in a davit gearbox may solidify under cold conditions. If the oil is contaminated then it should be replaced and the cause of the contamination determined and rectified. Excessive moisture in the gearbox may lead to braking system failure.
Uncovered survival craft, as well as the associated access ladder, should be protected from snow and ice by an appropriate cover.
Avoid material made from natural fibres for painters, embarkation ladders, ropes and protective covers because natural fibres absorb moisture resulting in a loss of flexibility and durability under cold weather conditions.
Ice accretion should be regularly removed from lifeboats and launching equipment. An ice removal wooden mallet should be available in the vicinity of the lifeboats.
6.11.2 Emergency Generator The following precautions must be taken:
• The emergency generator room space heater must be switched on, where fitted;
• If no heating is provided, then the emergency generator fuel tank must be filled with winter grade Gas Oil;
• Any water cooling of emergency generator engines must have an adequate amount of antifreeze in the coolant. The antifreeze mixture should prevent freezing to avoid damage to the cylinder block;
• The emergency generator must be run regularly in cold weather to ensure continued satisfactory operation.
Emergency generating sets should be capable of being readily started at a temperature of 00C. If this is impracticable, or if lower temperatures are likely to be encountered, provision should be made for heating arrangements.
Even though the emergency generator space may be heated, engineers must be aware that if the
Even though the emergency generator space may be heated, engineers must be aware that if the