Briefing Paper - Ice

OIL COMPANIES INTERNATIONAL MARINE FORUM

Briefing Paper for OCIMF Member

Chartering and Vetting Groups

The use of Large Tankers in Seasonal

First-Year Ice or Severe Sub-Zero Conditions

NOVEMBER 2008

OCIMF's mission is to be the foremost authority on the safe and environmentally

responsible operation of oil tankers and terminals, promoting continuous

Issued by the

Oil Companies International Marine Forum

OIL COMPANIES INTERNATIONAL MARINE FORUM

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© Oil Companies International Marine Forum

The Oil Companies International Marine Forum (OCIMF) is a voluntary association of oil companies having an interest in the shipment and terminalling of crude oil and oil products. OCIMF is organised to represent its membership before, and consult with, the International Maritime Organization (IMO) and other government bodies on matters relating to the shipment and terminalling of crude oil and oil products, including marine pollution and safety.

Terms of use:

The advice and information given in this briefing paper (“Paper”) is intended purely as guidance to be used at the user’s own risk. No warranties or representations are given nor is any duty of care or responsibility accepted by the Oil Companies International Marine Forum (“OCIMF”), the membership or employees of OCIMF or by any person, firm, corporation or organisation (who or which has been in any way concerned with the furnishing of information or data, the compilation or any translation, publishing, supply or sale of the Paper) for the accuracy of any information or advice given in the Paper or any omission from the Paper or for any consequence whatsoever resulting directly or indirectly from compliance with, adoption of or reliance on guidance contained in the Paper even if caused by a failure to exercise reasonable care on the part of any of the aforementioned parties.

TABLE OF CONTENTS

1 INTRODUCTION

2

PURPOSE AND SCOPE

3

ICE NAVIGATION RISK ASSESSMENT

4

VETTING FOR ICE NAVIGATION

5

COMMENTARY ON ICE CLASS NOTATIONS

6 ENGINE

POWER

7

THE WINTERISATION OF SHIPS

8

NAVIGATION OF LARGE TANKERS IN ICE

8.1 Icebreaker Escort of Large Tankers

9

OILS SPILLS IN ICE

10 PROFICIENCY OF SHIP’S CREW

ANNEX 1

COMPARISON BETWEEN THE ICE CLASS NOTATIONS

OF CLASSIFICATION SOCIETIES

ANNEX 2

WINTERISATION OF SHIPS – CONSIDERATIONS

ANNEX 3

ICEBREAKER ESCORT OF LARGE TANKERS

ANNEX 4

TUG SUPPORT WHEN BERTHING AND UNBERTHING IN

ICE

A4.1

Arrival

at

Jetty

A4.2

Departure from Jetty

A4.3

Operations at Offshore Terminals

ANNEX 5

OIL SPILLS IN ICE

ANNEX 6

ICE OPERATIONS TRAINING COURSE

ANNEX 7

EXAMPLE TASK RISK ASSESSMENT – OPERATING IN

ICE

ANNEX 8

ICE NAVIGATION CONTROL SERVICES

A8.1

Finnish/Swedish

A8.2

Russian (Baltic Ports of St. Petersburg, Primorsk,

Vysotsk)

A8.3

Other Baltic Ports/Countries

A8.4

Russian Far East Navigation of Large Tankers in

Ice Conditions

A8.5

Canada

ANNEX 9

HELCOM RECOMMENDATIONS ON SAFETY OF WINTER

NAVIGATION IN THE BALTIC AREA

ANNEX 10

TRAFFIC SEPARATION SCHEMES AND MANDATORY

1. INTRODUCTION

Ice navigation and icebreaker-escorted navigation of large tankers is a concept that may be relatively new to many OCIMF member companies. With changes that have occurred in the Russian Federation, the tanker market has experienced an increase in the export of crude oil by large tankers from Baltic terminals impacted by the potential for winter ice navigation. This trend will continue elsewhere in the world as crude export terminals are established in other ice navigation areas such as the Barents Sea, White Sea and in proximity to Sakhalin Island (Eastern Russian Federation).

Some sectors of the industry have been used to dealing with the more-traditional high ice class smaller tankers designed specifically for escorted or unescorted ice transit. What is relatively new to the industry is the increase in demand for larger-size crude tankers of low, or no, ice class to trade out of an increasing number of ports subjected to first-year ice formation.

In the light of the experience of OCIMF members with the ice navigation of large, low-powered ice class tankers in the Baltic, and with a view to providing broad guidance to industry with regard to export projects involving the ice navigation of large tankers, OCIMF initiated the formation of a small group of specialists, the ICE Sub-Committee. The ICE Sub-Committee produced the first edition of this Briefing Paper in 2003 and has remained responsible for ensuring that the guidance continued to be current and reflected members’ experiences. This latest edition is produced in support of this aim and the opportunity has also been taken to re-structure the document to provide improved focus to the guidance.

2. PURPOSE AND SCOPE

The purpose of this paper is to provide guidance to the chartering and vetting groups of OCIMF members on the safe operation of tankers in areas affected by seasonal first-year ice.

Areas commonly affected by first-year ice include the Baltic Sea and Gulf of Finland, White Sea, Barents Sea, Eastern coast of Canada, Cook Inlet and in the proximity of Sakhalin Island in the Eastern Russian Federation.

The guidance in this paper is primarily aimed at the use of low, or no, ice class tankers from 50,000 tonnes deadweight upwards likely to encounter first-year ice. The paper does not attempt to address established or specialised ice trades utilising high ice class tonnage.

It is recommended that OCIMF members limit the use of low, or no, ice class ships in ice covered areas and non-winterised ships during severe sub zero temperature conditions. For the purpose of this paper, ‘severe sub-zero’ conditions are defined as forecasted daily mean ambient temperatures below -25°C.

The chartering groups of OCIMF members will be aware of the different types of ice clauses in common use in charter parties. This paper does not deal with the validity or otherwise of specific clauses and members are advised to consult their own commercial or legal advisers for advice on such issues.

General guidance on the various national and regional ice navigation systems is contained within annexes to the paper. This may be of particular use in clarifying some of the developments impacting on the movements of hydrocarbons from ports within the Russian Federation.

3. ICE NAVIGATION RISK ASSESSMENT

Many charterers and operators have a formal Hazard Risk Assessment process in place and conduct Hazard Risk Analysis when changes to activities lead to significantly higher risks or when circumstances create uncertainty over the safety of an operation.

It is therefore recommended that the operation of tankers in ice is subjected to a formal risk assessment process in accordance with individual company guidelines. When considering chartering any vessel, particularly large crude tankers or ships with no, or low, ice class notation, for voyages that include the potential for ice navigation or icebreaker escort, it is recommended that charterers and operators conduct hazard risk assessments. The following are amongst issues that should be considered for risk prevention or mitigation:

• Ice class notation; winterisation class notation • Ice certificate

• Appropriateness of insurance coverage in place due to breach of the Institute Warranty Limits (IWL). Ascertain limitations that may be described in individual charter parties, if applicable, or the ship’s insurance.

• Double hull

• Sufficient engine power available for use

• Operational duration in propulsion machinery critical range (with particular reference to the harmonic constant of LNG membrane tankers)

• Increased reserve bunkers and stores

• Compliance with items or procedures and precautions in place, as listed under Section 4 ‘Vetting for Ice Navigation’

• Use of Ice Advisors (particularly if the ice navigation experience of the bridge team is limited)

• Assessment of ice and weather forecast services • Convoy strategy, including ship’s position in convoy • Availability of icebreaker escort

• Navigational risks in ice, including besetment • Crew experience and training

• Increased manning levels (particularly bridge team)

• Additional arrival UKC (allowance for ice accretion impact on draft and trim) Annex 7 contains an example of a ‘Task Risk Assessment for Operating in Ice’ which is provided for information.

4. VETTING FOR ICE NAVIGATION

Depending upon the proposed trading areas, when intending to charter tankers for voyages where low temperatures, associated with ice navigation and/or icebreaker escort, are expected, the following basic issues relating to the ship's particulars or operating procedures should be considered as part of the risk assessment process, particularly if the vessel is not ice classed or of low ice class notation.

When considering a ship for a fixture, the intended voyage should be checked to determine if a breach of the Institute Warranty Limits will occur. If this is the case, appropriate action should be taken and the individual charter parties or, if applicable, ship’s insurance, should be reviewed and arrangements made with the ship’s owner or insurer, as appropriate.

It is critical that the significance of the ice class notation is understood. Ice class notation alone does not automatically imply that the ship itself is suitable for commercial operations in extreme (cold) environmental conditions. The fact that the hull has an ice classification means that it has been constructed to incorporate the minimum required speed/power output in ice and has hull structural integrity that allows the ship to navigate in seasonal first-year broken ice up to classification limits. Beyond these limits, additional measures, such as the use of icebreakers, will have to be taken.

‘Ice classification’ refers only to structural strength, propulsion power and arrangements. The fact that the hull is classed in this way gives no indication of the ship’s suitability to operate in very low temperature environments. The recently-introduced, optional ‘winterisation’ class notation provides an indication of the preparation of the ship to operate to an acceptable standard in extreme cold conditions where icing of the ship can be experienced.

Reference should be made to Section 5 for further information on ice class notations, Section 7 for winterisation, and to Annex 1 for a comparison of the differing ice class notations used by Classification Societies. It should be noted that, when reviewing the data in Annex 1, it is not always possible to determine direct equivalence between the various notations.

Chartering and vetting groups should ensure that ships intended for operations in extreme (cold) environments are capable and properly prepared. This includes the provision of adequate suitable equipment, preparations for equipment protection and procedures established to ensure safe operation and personnel welfare. The following list outlines areas that should be considered when chartering ships for operations involving low temperatures, associated with ice navigation and/or icebreaker escort. It is recommended that operators produce a suitable checklist to cover these requirements.

Classification

• Ice Class Notation (refer to Annex 1) Certification for Russian Ports

Ships entering Russian ports or bound for Russian ports may require an additional “Ice Certificate” in accordance with local regulations. This process assesses a ship’s suitability to operate in ice conditions and considers the following aspects:

• ice performance, including ice class

• speed and manoeuvrability characteristics in ice • compressive hull strength

• predicted ice conditions. Charter party / Insurance

• Hull and machinery insurance Institute Warranty Limits (IWL) should be checked.

Crew Proficiency

• Do the Master and navigation officers have suitable experience of navigation in ice or operating in extremes of cold weather?

• Are navigating officers provided with basic ice navigation training? (Refer to further guidance in Section 10)

Bridge Equipment

• Provision of high definition radars • Provision of infra red cameras • Heated wheelhouse windows

• Searchlights - number, position, method of control, power and suitability for operation in ice and snow

• Preferably enclosed bridgewings Hull

• Are systems in place to keep essential sea chests free of ice?

• Is steel suitable for exposure to low temperatures for voyage duration?

• Can propeller be kept sufficiently submerged below expected level ice conditions?

• Are accommodation heating systems adequate?

• Are systems in place to prevent freezing or snow blockage of essential air intakes and venting systems (including cargo and ballast venting systems)? Procedures and Precautions

• Does the operator have procedures and/or precautions in place that include the following:

ƒ Assessment of ice navigation and cold weather operational risks? ƒ Conduct of ice navigation/icebreaker escort navigation?

ƒ Receipt of ice navigation information (e.g. ice charts, satellite images)?

ƒ Cold weather operation and protection of, and access to, fire fighting systems, life saving appliances, critical equipment and deck machinery, including mooring equipment?

ƒ Prevention of freezing of services on exposed decks including fire lines, air systems, control systems and instrumentation?

ƒ Prevention of freezing of cargo and ballast systems including ballast water and venting systems?

ƒ Prevention of dangerous ice accretion?

ƒ Provision of adequate cold weather clothing and PPE for crew?

ƒ Provision of suitable tools and material for prevention and removal of ice and snow on board?

5. COMMENTARY ON ICE CLASS NOTATIONS

There is a wide range of ice class notations assigned by different Classification Societies and National Authorities. Ice classes cover different ship types and services, such as, cargo ships, icebreakers and tugs. For the purposes of this briefing paper, ice classes for tankers normally come under the banner of cargo ships intended for service in light ice to medium first year broken ice conditions. Ice class requirements are based on structural strength, propulsion power and arrangements with regard to ice thickness. The different levels of ice class notations are defined according to the nominal operational ice thickness. The rules pertaining to ice class notations deal with:

• Hull reinforcement - "ice belt" area from bow to stern between ballast and load water lines divided into forepart, midships and aft parts.

• Minimum engine power (linked to bow form of the ship) – the Baltic regulations from the Finnish-Swedish ice class rules as applicable to ships built after 1st September 2003.

• Additionally, the ship should have sufficient power for possible independent movement at a minimum steady speed of 1-2 knots, through an ice thickness determined through calculations based on the ice class of the ship.

• Rudder reinforcement and fittings. • Propeller, shaft and gears.

• Stern design.

• Sea chests and cooling systems. • Engine starting systems.

It should be noted that individual States or ports may require specific levels of ice class notation.

For further information on ice class notations, reference should be made to the appropriate Classification Society rules.

Most Classification Societies have their own individual ice class notation. The Finnish Maritime Administration (FMA) provides an easy to use reference document, FMA Bulletin 4/2.4.2007. It is available at their Website http://www.fma.fi/

Reference should also be made to Annex 1 for information on the differing ice class notations used by Classification Societies. It should be noted that when reviewing the data in Annex 1, that it is not always possible to determine direct equivalence between the various notations.

6. ENGINE POWER

The engine power of ships operating in the Baltic has traditionally been governed by the Finnish-Swedish Rules with tables and mathematical formulae. These are predicated upon maintaining a minimum speed of 5 knots in broken first year ice. The majority of ships classified using these rules are less than 50,000 metric tonnes. As the size of ships being classified for ice navigation has increased up to and including Suezmax, other methodologies, such as ice model tests, have been used to provide evidence that this minimum speed requirement can be met with less power than that calculated using the formulae. The power requirement depends on the basic design, including hull and bow forms to reduce resistance to encountered ice, modification of power plant, propulsion and propeller design to achieve the necessary thrust and, hence, the ability to reach the minimum speed requirement.

7. THE WINTERISATION OF SHIPS

The ice class notation covers a ship’s structural strength, propulsion power and arrangements. The notation does not cover suitability from the standpoint of commercial operability in low temperatures, ice navigation and/or icebreaker escort.

Some ice class ships may have voluntary additional notations, generally referred to as ‘winterisation’ or ‘de-ice’ notations. These notations will embrace technical and operational issues to minimise risk when operating in ice or severe cold conditions. It should be ensured that ship operators have written procedures addressing risk minimisation when preparing for and operating in cold weather and ice.

Preparations should be such that no aspect of safety is compromised while the ship is operating in cold weather conditions. Annex 2 provides detailed advice on winterisation.

8. NAVIGATION OF LARGE TANKERS IN ICE

Large conventional tankers are normally designed for optimum performance in open water. This applies to designs for hull form, rudders and propellers. Large conventional tankers perform relatively poorly in ice, for a number of reasons, including the following:

• they are more difficult to manoeuvre in ice

• propellers designed for optimum open water performance may not be suited for delivering maximum thrust in ice

• propellers and rudders designed for open water operation may be more susceptible to ice impact damage.

Given the above, it is strongly recommended that the propeller is kept as deep as possible and it should always be deeper than the thickness of level ice to be navigated. If conventional tankers have to go astern in ice, the rudder should always be placed amidships. The speed of the ship should be controlled to reduce the risk of ice damage. However, large tankers may find that, once stopped in ice, regaining momentum is difficult without icebreaker assistance.

‘Besetment’, or getting stuck in ice, is a risk that the Master of a large tanker should be aware of when navigating in ice. Ice under pressure can cause local forces on the ship's hull that may result in damage to plating, structure or hull coatings.

The waterline coating systems of tankers may suffer heavy abrasion damage in ice. In addition, some impact deformation of hull plating is possible. Charterers may wish to consider arranging independent inspections of the hull before and after ice voyages.

Where a ship’s officers and crew are not particularly experienced, the use of an Ice Advisor may be considered in order to supplement onboard knowledge.

8.1 Icebreaker Escort of Large Tankers

Charterers should be aware that large tankers are likely to require icebreaker assistance. The icebreaker escort of large tankers is not a subject that can be easily condensed. However, for the purposes of this Briefing Paper, it is considered useful to provide some basic information and this is contained in Annex 3.

In addition, the use of tugs to assist in berthing and unberthing operations is addressed in Annex 4.

9. OIL SPILLS IN ICE

The scope of the Shipboard Oil Pollution Emergency plan (SOPEP) of tankers operating in ice should address specific issues associated with the response to oil spills in such conditions. Operators should demonstrate that attention has been paid to the unique hazards posed by spills in the extreme cold or in ice. Annex 5 contains an overview of the issues that need to be considered.

10. PROFICIENCY OF SHIP’S CREW

It should be noted that the safe operation of a ship trading in ice requires skill and technical proficiency in excess of those required during normal operating conditions. It is, therefore, important that suitable training is offered to complement existing experience.

A ship’s officers and crew should be adequately trained for circumstances likely to be encountered when operating in low temperatures, undertaking ice navigation and/or icebreaker escort. This may take the form of in-service training, simulator training and/or Computer-Based Training (CBT).

It is recommended that the ship’s officers and crew have experience of trading in ice and a suggested experience guide for key personnel is as follows:

Suggested Ice Sailing Experience

Superintendent 2 seasons

Master 2 seasons

Chief Officer 1 season

Chief Engineer 1 season 2nd _{Engineer part season}

When reviewing the experience and training of ship’s officers, it is preferred that experience is gained in the rank that they are serving onboard, although it is recognised that this is not always achievable.

ANNEX 1: COMPARISON BETWEEN THE ICE CLASS NOTATIONS OF CLASSIFICATION SOCIETIES

For the ships the keels of which are laid or which are at a similar stage of construction on or after 1 September 2003. (In accordance with Bulletin No. 4/2.4.2007 of FMA)

№

RS Russian Register

GL DNV BV LR RINA ABS NK Finnish-

Swedish Ice Class

1 LU 5 / Arc 5 E4 ICE - 1A* 1A SUPER Ice Class 1AS FS(+) Ice Class 1AS FS

1 A Super 1 AA 1A Super

1A Super

2 LU 4 / Arc 4 E 3 ICE - 1A 1A Ice Class 1A FS(+) Ice Class 1A FS

1A 1 A 1A 1A

3 LU 3 / Ice 3 E 2 ICE - 1B 1B Ice Class 1B FS(+) Ice Class 1B FS

1B 1 B 1B 1B

4 LU 2 / Ice 2 E 1 ICE - 1C 1C Ice Class 1C FS(+) Ice Class 1C FS

1C 1C 1C 1C

5 LU 1 / Ice 1 E ICE - C 1 D Ice Class 1D 1D 1D

ANNEX 2: WINTERISATION OF SHIPS - CONSIDERATIONS

The considerations for the winterisation of oil or gas tankers are structured according to the following broad areas:

1 General 2 Deck

3 Engine Rooms, Machinery and Systems

4 Safety and Lifesaving Equipment, including Medical 5 Fire-fighting Systems and Equipment

6 Pollution

7 Ice Accretion and Snow Accumulation

In the event that the nominated ship has a voluntary ‘winterisation’ notation, reference should be made to the details of the specific notation to determine the preparations that have been undertaken.

A2.1 GENERAL

All void spaces, empty tanks, chain lockers and spaces should be sounded prior to entering cold weather. If any water is found, it should be educted dry, as far as is practical, to avoid ice damage when these residues freeze. The spaces should be regularly sounded to ensure that they remain water-free.

Sounding pipes, vents and remote gauges should be protected and remain operational as far is possible.

Valves

Hydraulic cargo or COW valves on deck should be protected with canvas covers and the valves should be frequently activated while in sub-freezing temperatures to avoid freezing/blockage. Portable steam hoses and connections for the manifold areas are quite important. If any water is present in valve gear boxes, when frozen, it will inhibit the opening of the valve.

If any valves are left ‘cracked’ open to avoid fracturing of valve bodies, it is advisable to mark each open valve on a pipeline mimic diagram.

Ballast Systems

Hydraulic ballast valves in empty tanks should be frequently activated to avoid freezing/blockage, unless other means are employed to prevent freezing. Ballast tank vents may become frozen if not protected by canvas covers or steam heating on passage. However, this could lead to over or under pressurisation of ballast tanks. The use of covers on these vents should be strictly supervised to ensure that the covered vents can still operate as designed. It is recommended that covers are removed prior to the commencement of cargo operations. Frequent removal of any accumulated ice will be required.

Cargo Systems

Cargo Tank P/V Valves

P/V valves should be thoroughly overhauled prior to entry into sub zero temperature area. Valves to be kept protected from ice accumulations on passage with canvas covers or steam heating. In extreme low temperatures, canvas covers have been shown to be more effective than steam heating. Before any cargo operation commences, it is recommended that covers are removed and that pressure/vacuum arrangements are free of ice blockage. In particular, check that drain holes are clear and free to operate. The painting of Hi-Jet seat faces with anti-freeze will protect them from freezing in the shut position and will prevent an ice film forming.

IG Deck Seal (Heating)

The deck water seal heating must be operational in freezing temperatures. It should be ensured that the inlet/outlet of sealing water is not frozen and/or blocked by ice. Frequent checks should be undertaken to confirm a positive water flow.

P/V Breakers – Liquid (anti-freeze)

The deck breaker should be filled with anti-freeze (Glycol as opposed to Methanol based) as per maker’s instructions. Frequently checks should be undertaken to ensure the level is maintained. Once clear of the cold weather, the density of the P/V breaker will need to be tested and returned to the correct value necessary to ensure correct operation.

Mast Vent Riser (where fitted)

The mast vent riser valve needs to be protected with grease and a canvas cover. Flame arresters should be checked free of ice before the start of cargo operations. Prior to arrival, mast risers and inert gas (IG) lines should be drained of any liquid.

If fitted, auto and manual valves on the IG main line and tank inlets should be kept greased and protected with canvas covers. The operation of piston breather valves on IG lines should be checked before operations commence. Covers should be removed and de-icer sprayed in way of the valves.

It is recommended that the diameter of drainage lines on mast risers systems should be at least 50 mm

Cargo Pumps

Deepwell pumps

Motors and shafts of pumps, located on deck, should be protected with canvas covers to avoid delays due to de-icing pumps before discharging. ‘Framo’ Style Hydraulic Systems

The grade of hydraulic oil used in the Framo pumps is satisfactory for air temperatures down to -25°C without causing any problems. If the oil temperature falls below +25°C, the heating valve to the system should be opened. The Framo system should be started on low load with forward warming through valve open, at least 30 minutes before the system is required for operations.

If the temperature of the hydraulic oil is less than +20°C, it must be heated before the pressure can be increased. This is achieved by running a power pack with minimum system pressure (60 Bar), and opening the bypass valve on the cargo main deck forward to circulate the oil. Once the temperature is above 20°C, the bypass valve is closed and the pressure can be increased to operational requirements. It should be ensured that the oil is warmed through in good time before mooring as it takes approximately one hour to increase the temperature by four degrees centigrade in freezing conditions.

It has been stated that some thickening of the hydraulic oil due to the increased viscosity will be experienced when ambient temperatures fall to zero and below. Minimising dead legs will assist in the pump’s operation and, when starting the pump initially, it should be started very slowly to enable the warm hydraulic oil from the main to slowly displace the cold oil in the pump and consequently warm the pump through slowly. An increase in the normal loading may be placed upon the supply pump on starting a hydraulic pump due to the change in viscosity of the hydraulic oil.

Cargo Residue Tank Pump

Some tankers have a small screw pump on the main deck for pumping oil residues ashore. This pump must be drained down and isolated to prevent fracturing of the pump casing.

Cargo Stripping Systems

Any systems using water seal vacuum pumps need both the pumps and the seal supply header tanks to be protected from freezing. The manufacturer’s recommendation should be followed and the required percentage of anti-freeze added to ensure safe operation.

Crude Oil Washing (COW) & Tank Cleaning Systems

COW machine gearboxes should be protected with canvas covers. Gearbox oil should be renewed, particularly if the presence of any moisture is suspected to avoid damage. Tank cleaning lines should be drained of all water and isolated from the drive system. If tank cleaning is to be undertaken in cold regions, the sub-division of the cleaning system should be reviewed to limit the amount of pipe-work containing water.

Cargo Tank Heating Coils

If not in use, heating coils and lines should be drained and blown through with air. Steam delivery lines should be blanked off (deck steam supply line required for steaming hoses, but must not be allowed to compromise heating coil integrity through leakage and subsequent freezing in lines).

Consideration should be given to opening the plugs under the COW isolator valves to drain down any water in the seat of the valve.

Tank Cleaning Heater

When located in an exposed location, this will need to be protected and, in any event, should be drained.

Cargo Lines

Differences in temperature experienced by the ship can cause contraction of the deck lines that may not be taken up in the usual manner. There is a possibility of flange leakage and it would be prudent to check the integrity of the lines that are to be used to ensure they are tight for the forthcoming operation.

All cargo, ballast, tank cleaning and COW lines on deck should be well drained after pressure test or use. Particular attention should be paid to ballast systems, including ballast monitors and lines. After loading, discharging or bunkering in cold climates, ship’s lines should be drained and drain valves left open until the ambient temperature rises sufficiently. Where possible, it is recommended that at least one tank filling valve is left open to allow the line to drain and preclude the possibility of the line becoming pressurised due to temperature changes.

The pour point of the cargo being carried or to be loaded should be checked to determine whether line blockages may occur if cargo operations are stopped for any reason. Similarly, bunker fuel specifications should be checked for pour point.

Ice Accretion on Deck Fittings and Cargo Valves Pump Rooms

Without compromising safety, pump room fans should be used only as required for ventilating the space to minimise the effect of sub-zero temperatures inside the pump room. Pump room doors should be kept closed, if possible.

Steam lines in the pump room, including those serving the tank-washing heater, should be drained down. The stripping pump, if fitted, may be kept warming if it is required to be ready for cargo operations or, alternatively, to provide some warmth in the pump room.

If fitted, pump room heaters should be turned on and, if provided on different floors, at least one on each floor should be used to promote convection currents in the space.

Oil Discharge Monitoring Equipment (ODME)

The fresh water supply to the ODME should be drained down together with the water supply/flushing pump.

Particular care should be taken when isolating and draining down the ODME as this is a well-documented weak spot on ships in cold climates.

Prior to entering cold conditions, all cargo, bunker, ballast and subsidiary valves that will be required to be used for the forthcoming operation should be inspected to ensure that their gearboxes contain no water and are well greased. A small amount of water in the gearbox of a hydraulic valve, or in the valve bonnet, will, when frozen, have a detrimental effect upon that valve and, in extreme cases will render the valve inoperable. Care should be taken when forcibly removing ice from machinery and equipment to ensure that the equipment is not damaged by the use of hammers or tools.

Ice Accumulation in Ballast Tanks

Before entering cold climates, the Master should determine the density of the ballast water contained within the ballast tanks. The more saline the water is, the lower the freezing temperature will be. Consideration may be given to exchanging the ballast water to increase its salinity.

The surface of ballast water may freeze in ballast tanks. A considerable danger exists whereby during de-ballasting operations a layer of ice remains suspended in the tank, falling at a later time, causing damage to internal structure and fittings. If possible, ballast levels should be kept at or below the level of the sea surface (but also be aware of dangers of having sea suctions too close to sea surface getting blocked with sea ice).

Where fitted, ballast tank heating (or bubbling systems) must be in operation prior to entering areas with sub-zero temperatures, particularly when ballast levels are above the water line.

If stability and the ice belt depth allows, where no ballast tank heating or bubbling systems are fitted, periodic lowering of the ballast level may avoid freezing of the water surface.

A2.2 DECK

As well as the natural consequences of sub zero temperatures, e.g. freezing of liquids, another area that should be managed is the accumulation of ice on deck from freezing spray and rain. Consequently, many of the actions below relate to covering equipment with canvas, heavy-duty plastic sheet or similar. Ice accumulations on unprotected equipment will render the equipment inoperable.

Oil spill equipment should remain inside deck houses to prevent icing up if wet, but it should remain ready for use.

Tank gauging/dipping point valves should be covered to prevent ice accumulation. Cargo manifold pressure gauge connections should be covered to prevent ice accumulation

Cargo Manifold drip tray should be maintained dry. The drain valves on the drip tray should be drained of any water to prevent freezing in sub zero temperatures as well as be operational for draining cargo from loading arms into the drain tank.

Cargo handling Cranes/Derricks- should be operated and tested prior entering sub-zero temperatures. Heating arrangement provided should be used appropriately.

Accommodation Gangways – Pneumatic/Electrical motors should be adequately covered to prevent ice accretion.

Action should be taken to prevent scupper holes from getting iced over and scupper plugs not fitting correctly. Coating the scupper plug rubber faces with petroleum jelly will prevent seizure of the plugs in scupper holes.

The main air valve to deck should be closed and the airline drained down, taking care to remove any moisture that may be contained within the, line especially at the ends. Deck Mooring Equipment

For hydraulic equipment, for example, winches and hose handling cranes, particular attention needs to be paid to the operating temperature range of the hydraulic fluid. For hydraulic driven systems, oil should be circulated all the time when external temperature is below 0°C so as to ensure that the fluid systems are maintained at working temperature. If this is to be achieved by leaving machinery (e.g. winches) running, careful attention must be paid to the regular lubrication of the equipment. The oil manufacturer’s stated operating temperature range/viscosity must be checked for suitability. Oils may have to be treated with an appropriate viscosity additive or, in extreme cases, the oil may have to be changed for a more suitable grade.

If a ship trades extensively within cold climates, a reduction of hydraulic line life can be expected. This can be up to 25% of the manufacturer’s advertised life for these products.

Control boxes and motion levers should be protected by canvas covers. Ice Accretion on Windlasses

Mooring wires and synthetic ropes should be protected by canvas covers to stop ice accretion until they are required for use. If any mooring ropes have to be left out on deck, they should also be covered with canvas to stop ice accretion. The clutches and engaging gears of winches should be well protected by substantial coatings of grease.

Other

Particular care should be taken in sealing the chain locker spurling and hawse pipes.

Prior to arrival in port, both anchors should be lowered so that they are free to run from the pipe (i.e. not frozen in) when safe navigation permits. However, they should be fully brought home when mooring and unmooring.

Sprinkler Systems

Sprinkler systems should be drained down free of water. This should include sprinkler systems to chemical, paint and other store rooms, mast riser systems and any fresh or salt water systems covering other spaces.

A2.3 ENGINE ROOMS, MACHINERY AND SYSTEMS

Prior to entering cold weather areas, the engine room should be prepared for the anticipated conditions. Particular consideration should be given to deciding when the engine room should be manned.

The provision of heaters in the engine room/machinery spaces will assist in maintaining temperatures above freezing. The use of hot-air-blown space heaters may also be considered within these spaces.

The following points should be considered to maintain the safe and effective operation of the ship’s propulsion and subsidiary systems.

Cooling System Intakes (Sea Chests)

Cooling water generally is going to be a problem in sub-zero sea temperatures. Prior to entering cool water, it is important that all seawater strainers are cleaned since a slightly clogged filter will lead to reduced flow, resulting in rapid ice formation within the strainer.

Ships that are not fitted with a system as specified by authorities, such as the Canadian Coast Guard, should exercise vigilance to ensure that heating arrangements of the cooling water sea chests are working at optimum efficiency. The machinery space should be constantly manned to ensure adequate and prompt action. If cooling water becomes too cold, reduce flow and/or bypass cooler water inlet with outlet. Should the flow become inadequate due to the build-up of ice on the sea chest, RPM should be reduced, plugging the intake until the heating system restores conditions to normal.

The steam heating system to all sea chests should be checked for good working condition and then kept operating when the ship is in ice infested waters. Flexible steam hoses should be connected to the sea suctions prior to arrival in ice or cold waters.

Consideration should also be given to the following:

• It may become possible to severely overcool the jackets, something that should be avoided

• Shut down to one central cooler

• Sea water system – main sea water system in engine room set up for re-circulation to sea chest with steam connections ready for use

• Adjust charge air coolers

• Monitor closely the scavenge temperatures and ensure that they are maintained within limits.

Fuel System

Ensure steam heating is operating on all bunker storage tanks, bilge tank, bilge overflow tank, main engine sump settling and service tanks. Bunker storage tank temperatures should be kept at least 5ºC above the minimum transfer temperature given in the fuel’s specification.

Consideration should be given to changing over from heavy fuel oil to diesel oil prior to closing down the main engine so that the fuel lines are primed with diesel oil instead of fuel oil. This ensures that any cooling of fuel lines will not result in oil solidifying within the lines.

Cargo Pumps

If fitted, ensure cargo pump steam inlet lines are completely drained of condensate to avoid damage to pipe work.

Run cargo pump lube oil priming pumps to ensure lubricating oil remains at a satisfactory temperature and does not become too viscous.

Stern Tube

Stern tube oil should not contain any free water or be contaminated with water/oil emulsion. Consideration should be given to draining any water from the system or replacing the stern tube oil charge.

The temperature of the stern tube cooling water tank should be closely monitored. Consideration should be given to sourcing a suitable additive or temporarily draining the tank when the contents approach 0º C.

Ventilation

Consideration should be given to stopping all but one main engine room ventilation fan to maintain a reasonable ambient temperature in the machinery space. However, suitable air flow must be maintained to allow the correct operation of boilers, main and auxiliary engines if they are not provided with separate ducting.

Ensure, so far as possible, that vents feeding off the main ventilation system do not blow directly on to fuel lines or pipes containing fuel oil. Likewise, ensure that these vents are not blowing onto the heavy fuel oil transfer pumps.

Stop ventilation fans in the steering gear space and close fan flaps to maintain a reasonable ambient temperature.

Activate accommodation steam heating and maintain a comfortable temperature and humidity in accommodation spaces.

Regularly operate pneumatic and manual fan flaps to ensure their correct operation and avoid seizing.

Machinery

Electrical Systems

Portable space heating tape is an adhesive tape with wire contained in it that can be used to heat pipes and machinery. It comes with the necessary documentation to calculate current, load and wattage. It provides a temporary, quick and cost-effective solution to heating pipes and machinery. It is not “IX EX” approved and is therefore suitable for use only in non-hazardous areas.

Electrical motors not fitted with electric space heaters should be checked. Generators

The fuel temperature of any generator running on gas oil/diesel should be monitored and arrangements made for temporary local heating if the temperature approaches the fuel’s pour point.

Emergency Generators

Some ships have emergency generators that have electric heating on the alternator end. This should be tested to ensure satisfactory operation.

The emergency generator room external vent flaps and supply fan damper should be kept closed. Notices advising of the status of the flaps and dampers should be posted in the emergency generator room and main engine control room. It should be ensured that the emergency generator has the correct amount of anti-freeze added to the cooling water.

Reference should be made to Maritime and Coastguard Agency Marine Guidance Note MGN 34 (M+F) Lifeboat Engines and other Compression Ignition Engines used

in an Emergency, copies of which can be downloaded from the MCA site at

http://www.mcga.gov.uk/c4mca/mgn0034.pdf

Emergency Batteries

Emergency batteries and power for communications’ equipment should be protected from extreme low temperatures. Spaces containing batteries may need to be provided with space heaters, dependent upon their location/exposure.

Battery Lockers

GS batteries (maintenance free type) and GMDSS batteries (water/acid mixture) are unlikely to freeze in expected conditions but, as a precaution, can be covered with plastic sheet.

Water

When not Generating Water

Domestic/Distilled Tanks. Ensure that, where possible, gauge glasses are drained. If gauge glasses are not drained, there is the possibility that the lower section of the gauge glass will become frozen and shatter. Remote sensing gauging cannot be relied upon. If the evaporator is not in use, drain the line as this may freeze.

When Generating Water

Monitor the temperature in the water storage tanks and make water to tanks as necessary to maintain a reasonable temperature. As the distillate from the evaporator is at about 50°C, this should prevent the water in the tanks becoming cold enough to freeze.

The supply lines from domestic fresh water tanks to pressurising pumps are generally susceptible to freezing, depending upon their location.

Boiler water sensing lines should be protected from freezing Compressed Air

If ice contaminates the general service and or instrument air system, there is the possibility of problems with on board instrumentation air supply, and also there is the possibility of blowing the general service air main valves.

Rudder & Steering Gear

Steering gear motors should be kept running at all times to keep the oil warm. Space heaters should be used in the steering flat to ensure no cold soak of the equipment takes place and also to protect the gauging system of any fresh water storage tanks that may be contained within the steering flat.

Lubrications and Oils

It should be ensured that only suitable winter grade oils are used. These will typically be effective down to temperatures of -20ºC with only increased viscosity to be contended with.

Reference should be made to Maritime and Coastguard Agency Marine Guidance Note MGN 34 (M+F) (see under ‘Emergency Generators’ above).

Winter Grade Diesel Oil Blend

The following information is intended to enable blending of fuel to achieve a calculated pour point. It is important to realise that a pour point of -15°C would not give an engine start requirement at an ambient of -15°C. Hence, the ISO DMX spec is based upon a cloud point value. The reality is that an engine may fail to start at some temperature lower than the cloud point because wax crystals have formed, causing blockage and fuel starvation.

Diesel to the ISO-8217-DMA spec or equivalent should be purchased and the pour point for the fuel obtained. For calculation purposes, it is assumed to be the summer specification, which has a pour point of 0°C. On this basis, the following ratios will give target pour points as follows:

Ratio Diesel/Kerosene Pour Point

°

50/50 -14 40/60 -18 30/70 -23 As the proportion of kerosene is increased, there is a risk of exceeding the flash point minimum of 43

°

°

A2.4 SAFETY AND LIFESAVING EQUIPMENT, INCLUDING MEDICAL

Periodic inspections of all safety related systems should be undertaken during the exposure to extreme temperatures to ensure that the precautions being taken are effective.

All available space heaters and engine sump heaters/heat lamps should be fully utilised. Ships that do not regularly trade in such conditions may require the purchase of additional protective equipment.

Life rafts

All life rafts should be rated for safe operation down to temperatures of -30°C.

Ice accretion should be regularly removed from the life rafts, cradles, cradle release pins and launching equipment to ensure ease of launching and inflation. An icing removal mallet should be readily available in the vicinity of the life rafts. Care should be exercised when using mallets to avoid permanently damaging any equipment. Similar precautions should be taken for lifeboats, rescue boats and their launching appliances. Particular checks should be made to ensure that brake release securing pins are free to be extracted.

Lifeboats

The overall condition of the lifeboat’s gel coat should be inspected, in good time, for any damage, particularly penetration of the gel coat and fibre sub structure. Any damage should be made good in a warm dry climate to limit water ingress, which, if subjected to freezing, can cause severe damage to the boat’s structure.

Lifeboat Engines

The lifeboat engine should at all times remain available for immediate use within two minutes of starting at -15°C. (SOLAS)

The process of starting an extremely cold engine is quite different from normal starting procedures. The correct procedure should be drawn to the attention of all persons likely to be involved in starting the engine in very cold conditions to ensure they are familiar with the operation.

Manufacturer’s instructions for the grade of oil to be added to the cold starting pots, if fitted, should be followed. This oil should be readily available in the lifeboats. The possibility for increasing the amount of throttle required on starting should not be overlooked. It should also be borne in mind that the performance of the starting batteries in cold conditions might be diminished.

If fitted, heaters in life boat engines should be used. Lifeboat Fuel Systems

“Winter Grade” diesel/gas oil is the grade that should be used to prevent waxing in fuel systems leading to lack of engine start and impaired reliability. The fuel tanks and line contents on lifeboats should be changed out and the engine run on new fuel to ensure the system is properly flushed and primed.

Reference should be made to Maritime and Coastguard Agency Marine Guidance Note MGN 34 (M+F) (see under ‘Emergency Generators’ above).

Lifeboat Cooling Water Systems

The lifeboat cooling system, if of a recirculating self-contained type, must be adequately protected with anti-freeze solution. If the system is not self contained, it should be checked to ensure that no obstructions or contamination has prevented the natural drainage of this system.

Lifeboat Water Spray Systems

The spray systems on the life boats should be drained and water-free. The pumps to the spray system should also be drained and water-free. In some classes of boat, if the spray pump is frozen, it will inhibit starting of the lifeboat engine by locking the propeller shaft.

Lifeboat Bilges

These should be cleaned and dried and should remain water free. Lifeboat Water Ration Containers

Water in lifeboat containers will freeze. It should be ensured that sufficient space is allowed for expansion of the contents to prevent splitting of containers. A level of ¾ full is suggested. Additional containers will be required to ensure the water provision meets SOLAS requirements for each lifeboat.

Stern Launched Lifeboats

It is not safe to release a stern launched lifeboat into ice. When in ice, it will be necessary to break the ice, whether by judicial use of the ship’s engines or by other craft. The lifeboat may be winched out and down to rest upon the ice surface.

Rescue Boats with Water Jet Engines

The use of semi-rigid rescue boats, particularly boats with water jet drives, in ice conditions is a dangerous operation if not handled correctly. It will be individual Master’s decision as to whether to use the fast rescue boat or the more-substantial ship’s lifeboat with conventional propeller drive, which may be more suited to the prevailing conditions.

In any event, the engine of the rescue boat should be dry to prevent the seizure effect of any surface or ingested frozen water. The rescue boat should be maintained in a condition that will allow immediate use but will also protect the boat from the extremes of weather. Appropriate covers and protective measures should be taken to ensure this.

Subsidiary LSA Equipment Immersion Suits

Special immersion suits for Arctic waters are available and are recommended for ships operating in cold climates.

Commonly supplied immersion suits have a design operational range in immersed (seawater) temperatures from -1.9°C up to +35°C. Below -1.9ºC, the suit’s thermal protective properties will be reduced but it will still afford limited protection to the user.

TPAs (Thermal Protective Aids)

TPAs are effective within a temperature range of -30°C to +20°C. Lifebuoys

Ensure these are not iced into position and are free to be removed and used. External Pyrotechnics

Bridge wing lifebuoy/smoke floats’ release pins should be well greased together with the complete apparatus to ensure it remains ice-free.

EPIRBs

EPIRBs should be maintained ice-free.

Breathing Apparatus and Oxygen Therapy Units

In sub zero conditions, the use of compressed air/oxygen breathing or resuscitation apparatus should be considered with care. The hazards involved

include the freezing of the demand valve and exhale valve due to the freezing of exhaled vapours from the user leading to premature emptying of the gas bottle or failure of the system. The effect of low temperature (below -4°C) on the lungs of the user, can lead in protracted cases to frostbite of the lung tissue.

Eye Wash Stations

Eye wash fluid is effective in a fluid temperature range of +5°C to +25°C. Below +5°C the effectiveness of the fluid is reduced. At 0°C fluid temperature, it is strongly recommended not to use the fluid except in extreme urgency as it may cause damage to the eye. Consideration should be given to withdrawing temporarily exposed eyewash stations into the accommodation whilst the vessel is operating in sub zero conditions.

Hard Hats

The safe operating temperature range for hard hats is marked within the hat by the manufacturer. Some hard hats are certified for safe operation to -40°C and their use should be considered.

A2.5 FIRE-FIGHTING SYSTEMS AND EQUIPMENT

Precautions should be taken to prevent nozzles, piping and valves of any fire extinguishing system from becoming clogged by impurities, corrosion or ice build up. The exhaust gas outlets and pressure vacuum arrangements on gas detection systems should be suitably protected from ice build up that could interfere with the system’s effective operation.

Type of Extinguisher Minimum operational temperature Modified extinguisher Minimum operational temperature Maximum operational temperature Hazards

Water gas -20°C

if “Kerrol” or

an equivalent

additive is used.

N/A If

no

additive

water will

freeze at

CO2

_----

_{N/A Cold}

_burn

hazard

Dry Powder

_----

_{Cold burn}

hazard

AFFF

_----

_Nil

Operational Temperature Ranges of Portable Extinguishers

Fire Extinguishers (in exposed locations) Water Gas and Low Expansion Foam

Fire extinguishers located in exposed areas are susceptible to freezing. Foam extinguishers will be ineffective and, when they do thaw out, the foam compound will have been ‘frost damaged’, rendering them useless.

Unprotected water and foam extinguishers are rated for safe and effective operation to +1ºC. If protected with ethylene glycol, this figure is revised downward to -10ºC.

If the additive ‘Kerrol’, or equivalent, is used, this will enable water and foam extinguishers to be available for use at temperatures to -20˚C.

CO2 Extinguishers

CO2 extinguishers are rated for safe and effective operation to -20°C. However, if operated at these temperatures extreme caution should be taken to avoid contact with any part of the extinguisher or expelled gas to avoid low temperature burning.

Dry Powder Extinguishers

These types of extinguishers are rated for safe operation from -30°C to +60°C. The extinguishing medium presents no additional special precautions. However, the propellant, CO2 _{needs to be treated with extreme caution to} avoid personnel injury through exposure to the cold gas.

AFFF

AFFF (Aqueous Film Forming Foam) extinguishers have a nominal safe operational range of temperatures between +5°C and +60°C. At temperatures below +5°C, the operation of AFFF cannot be guaranteed.

Fire Mains and Foam Systems Hoses and Nozzles

There is no restriction on the use of fire spray nozzles down to -25°C.

Most hoses are rated for safe operation to temperatures of -20°C. Cold weather hoses are available that are rated to -40°C and are marked accordingly.

Fire and Foam Lines

The fire and foam lines on deck must be well drained, by opening drain valves and the lowest hydrant valve. Fire and foam lines must be ready for use at all times (not blanked). Monitors, hydrant valves and any other moving parts must be well greased and protected to avoid ice/snow accumulation that may prevent their immediate operation. Their movement should be regularly checked to ensure that they remain free for operation. In addition, the water curtain and spray system pipe work must be checked drained and empty. Also any items drawing from the fire main, such as hawse pipe cable washer lines, should be drained down, particularly if a re-circulatory fire main line is in use (to avoid any “dead-ends”).

Fixed foam system bulk storage tanks will need heating to ensure that the temperature in these spaces remains above zero. It may be necessary to source temporary space heaters to heat these spaces adequately.

Portable Foam Equipment

Drums and canisters of foam for portable branch pipe appliances are subject to the same sensitivities as portable fire extinguishers.

These should be kept ice-free on catches/locks/dogs/hinges to allow ease of access. Spray nozzles and couplings should be well greased and water free. All hoses should be completely drained of water to avoid damage and to facilitate their rapid use.

A2.6 POLLUTION

Prevention of pollution to the environment in areas of extreme cold is of great importance. Care should be taken to follow all regulations in force and particular to those areas the ship is trading in. An example of local requirements is the proposed prevention of grey water discharge while in the Baltic.

Changes to the pollution contingency plans should be made well in advance bearing in mind issues, such as, the reduction in the effectiveness due to ice accretion of gutter bars to mitigate loss of primary containment to the main deck.

The readiness of pollution equipment must not be compromised by the effects of ice accretion. If pollution equipment is stored forward, consideration should be made to stowing it in the after part of the ship where the possibility of icing is less.

The ship’s sewage system should be in good operating condition and suitable storage available in the event that discharge to sea is not permitted by local regulation.

A2.7 ICE ACCRETION AND SNOW ACCUMULATION ON SHIPS

Ice accretion and snow accumulation poses hazards for personnel having to work onboard the ship, as well as to the ship itself. De-icing a ship is a complex, time-consuming and expensive operation and ships generally are not well equipped to do the job. Masters should try to minimise, as much as possible, sea spray on deck by either reducing speed and/or altering course. Masters should bear in mind that entering thin ice will reduce sea spray and hence ice accumulation. It should be borne in mind that ice accumulation also results in a potential for falling ice and the associated dangers.

In certain conditions, ice formed of fresh water or sea water accumulating on the hulls and superstructures of ships can pose a serious threat. Fresh-water ice can form from fog, drizzle, rain or snow. Icing from seawater is generally experienced with air temperatures of below -2°C and in conditions of strong winds.

Radio and radar failure due to ice on aerials or insulators may be experienced soon after ice starts to accumulate.

Where deck icing is evident, additional care needs to be exercised when moving and working around the ship, remembering that ice can be found both on the external surfaces and, in some conditions, in internal spaces.

The following section describes the effects of ship icing and how best to avoid or mitigate its formation and impact.

Description of Sea Spray Icing

Sea spray icing is a serious hazard for marine operations in high latitude regions. Many ships and lives have been lost when ships sank, or became disabled, following

the accretion of ice on decks and superstructures. Large amounts of ice on smaller ships can raise the centre of mass so as to result in a catastrophic loss of stability. Capsizing, extreme rolling and/or pitching, and topside flooding can occur as a result of the loss of stability and extra weight from the ice burden. The effects of icing on a larger ship may have a significant financial penalty attached if it impedes upon the ability to discharge or load cargoes satisfactorily.

Effects of Icing and Ice Accretion Causes

Sea spray icing occurs when cold, wave-generated spray comes into contact with exposed surfaces and the air temperature is below freezing. There are two general factors to be considered—Environmental and Ship Characteristics.

Environmental Factors

The following environmental factors affect sea spray icing: 1. Wind speed

2. Air temperature 3. Water temperature

4. Freezing temperature of water 5. Wind direction, relative to the ship 6. Swell and wave characteristics

• wave size • wave length

• wave propagation direction

Factors 1-3 are the most important to consider when determining the potential for sea spray icing. Factor 4 is nearly constant, Factor 5 can be changed by altering the ship heading and Factor 6 is closely related to the wind.

Ship icing can occur when the following environmental conditions are present: • High wind speed - usually above 18 knots or 9 m/s but sometimes lower • Low air temperature - below freezing (-1.7°C)

The first two factors, high wind speed and low air temperature, are associated with cold air advection. Cold air advection often occurs after the passage of a cold front. It is most intense when air formed over continents or ice regions (i.e. Polar Continental, Arctic and Antarctic air masses) moves over open water in the late autumn (fall), winter or early spring. Long, closely-spaced bands of low level cumuliform clouds called 'cloud streets' are a sure sign that cold air advection is taking place over water.

The cold air advection, and associated serious icing, is most intense when an ice edge or shore is less than 200 kilometres (108 nautical miles) upwind. At further distances, the air becomes warmer and icing is less likely. Very close (less than about 5 kilometres or 3 nautical miles; the exact distance being dependent on the ship’s size) to a shore or ice edge, waves are not developed and, hence, there is protection from icing even when the above conditions are met.

In the Northern Hemisphere, icing is most likely to occur in the northern portions of the Atlantic and Pacific Oceans. It also can occur everywhere in the Arctic Ocean and in the Southern Ocean surrounding Antarctica.

Ship Characteristics

In addition to the environmental factors discussed above, the severity of sea-spray icing depends on ship characteristics. Icing can only occur when there is a source of water for wetting the deck, superstructure and other exposed parts of a ship. Some ship factors to consider are as follows:

• Ship speed

• Ship heading (with respect to wind, waves and swell) • Ship length

• Ship freeboard • Ship handling • Ship cold soaking

In general, for the same environmental conditions, there will be more sea spray reaching the exposed deck and superstructure areas when a ship is travelling faster, heading into wind and waves, and with lessened freeboard. Smaller ships will, in general, also experience more spray reaching these areas.

The graphs below illustrate sea spray icing potential as a function of wind speed and air temperature for a given sea temperature. These are slightly different from the graphs used by the US Navy (1988) because they are based on the most recent work by Overland (1990). The main difference is that the effect of cold seawater is emphasised more in the graphs shown. Generally, icing is not a problem at sea temperatures greater than 7°C, and no cases with higher temperatures were considered when the algorithm was derived.

Note: The above provides only an approximate guide for ships steaming into the wind and waves. The actual potential for icing depends on the type, load, and handling characteristics of a particular ship. Any Captain or bridge officer who is familiar with a ship should be well aware of the wind speeds which cause sea spray to reach the deck and superstructure and should base their assessment on the potential for icing on this knowledge.

Another ship factor to consider is cold soaking. When a ship has been in cold temperatures for a long time (two-three weeks) the body of the ship will remain cold even if the air temperature is warmer. In this situation, icing may be more severe than expected given the current environmental conditions. Prediction of Vessel Sea Spray Icing

Algorithm

The following algorithms have proven to be useful for predicting sea spray vessel icing. These algorithms were based primarily on reports from vessels.

Where:

PPR = Icing Predictor Va = Wind speed (m s-1)

Tf = Freezing point of seawater (usually -1.7°C or -1.8°C) Ta = Air temperature (°C)

Tw = Sea temperature (°C)

The following table shows the expected icing class and rates for ships that are steaming into the wind.

PPR <0 0 –22.4 22.4-53.3 53.3-83.0 83.0->

Icing Observation

None Light Moderate Heavy Extreme

Icing rate Cm/hr Inch/hr 0 <0.7 <0.3 0.7 – 2.0 0.3 – 0.8 2.0 – 4.0 0.8 – 1.6 >4 >1.6

These icing rates are only a guide. Actual icing rates depend on ship characteristics, cold soaking and exposure to sea spray.

ANNEX 3: ICEBREAKER ESCORT OF LARGE TANKERS

There are various different types, designs and sizes of icebreakers. Icebreakers used for escorting large tankers may be multifunctional or may have been designed with other prime or secondary purposes in mind. The world's icebreaker fleet is ageing and it is recognised that there is a shortage. Most escort systems work on the principle of providing icebreaker assistance only when the ship is bound to the port/country which also provides the icebreaker service.

In general terms, large conventional tankers may require icebreaking assistance in anything more than thin unbroken ice. The ice channel required by large tankers will usually be wider than the beam of the tanker. Two icebreakers may be required for efficient escort. However, depending on the circumstances, single icebreaker escort is also possible.

There is a range of different large-ship icebreaker escort techniques in use depending, for example, on the ice conditions, preferred methods of the local icebreaker Captains and availability/design of icebreakers. Azimuth stern drive (ASD) icebreakers can break significantly wider ice channels than their beam by directing the azimuth thrust forwards and outwards. Conventional, high power icebreakers can achieve wider ice channels than their beam by breaking thin or medium thickness ice at high speeds of advance.

A common mode of large ship escort consists of two icebreakers in tandem (one ahead of the other) and separated by about 20 metres (depending on the beam of the tanker). This provides an ice channel approximately the width of the combined beams of both icebreakers plus the separation distance. The tanker travels at a "safe distance" behind the nearest icebreaker at a "safe speed" nominated by the icebreaker Captain who controls and manages the convoy. The tanker will encounter ice floes in the channel, as illustrated in the Figure below.

The convoy Masters must be alert to the danger of collision between tanker and icebreaker, particularly if the icebreaker comes to a sudden stop due to ice ridges, deformed ice or pressure. Missing the ice channel at high speeds when navigating from open leads or nilas (thin new ice) into thicker ice is also dangerous for the following tanker. The tanker’s bridge team cannot be allowed to become fatigued and, if they are not familiar with this mode of operation, experienced assistance in the form of an ice advisor is recommended.

Good communications, defined responsibilities and adherence to well thought out procedures are extremely important to the safe execution of large tanker escort operations.