Layup & Shipcare with Asean Shipcare™ (ASC)
Laying-up ships makes good business sense during tough times. Not only does it allow ship owners and operators to avoid non-profitable journeys and over supply, it also reduces wear and tear, crew costs, fuel consumption and insurance premiums during the idle period.
ASC has prepared these guidelines as support for customers that opt to layup their vessels – whether it be for shorter or longer periods – and to provide a clear overview of the layup methods and services available.
- Shelter provided from open seas, winds, waves, swells etc.
- Mooring method including ships berthed alongside, at buoys, anchors, stern moorings, anchored rafts of several vessels, etc.
- Security of location.
- Proximity to preferred trading routes after reactivation.
- Detailed local weather conditions, such as:
- wind, waves and swell, direction and force;
- cyclones, hurricanes, ice, local currents and tides;
- reliability of local weather forecasting services.
- Shelter provided from open seas, winds, waves, swells etc.
- Anchorage depth and type of holding ground, with diver or sonar surveys as appropriate.
- Water depth to be sufficient for the vessel to remain afloat with sufficient under keel clearance at all tide conditions.
- Proximity to any obstructions, wrecks, underwater cables or pipes, etc.
- Proximity to passing traffic and other moored vessels.
- Proximity of any commercial aquaculture including fish farms, oyster beds, water intakes etc
- Details of local authorities and availability of tugs, fire fighting, medical and safety services.
- Availability of services such as fresh water, waste disposal, shore power and repairers
- Available space or number of designated layup positions
- Suitable access and egress channels, pilotage, tug assistance during mooring, etc.
- Likely hull fouling due to marine growth
- Location of any effluent or corrosive discharges
- Availability of spare or replacement mooring equipment
- Potential windage of vessels, containers on deck, etc.
- Facilities for shore monitoring of vessel position, remote GPS monitoring etc.
Laying-up a ship is designed to:
- maintain the security, safety and protection of the vessel, crew and environment;
- preserve and maintain the vessel structure and machinery by protecting against corrosion and static seizure.
The extent to which a vessel will be laid-up depends on several factors, including: anticipated layup period duration; the need to reduce running costs; time required for reactivation; and the age and value of the ship.
ASC offers four different modes of layup:
|Hot||up to 3 months||(H)|
|Warm||up to 12 months||(W)|
|Cold||up to 5 years||(C)|
|Long term||5 plus years||(L)|
Hot layup (24-hour reactivation)
This layup condition is suitable for up to a month out of service. In this condition, the vessel is held within Classification and Flag State requirements, although crew numbers may be reduced to certified minimum safety crewing limits. Machinery is kept operational but economies are made. The vessel is located in an area close to potential cargo trade routes.
Warm layup (one-week reactivation)
Suitable for up to 12 months out of service. In this condition, vessel crewing is reduced to below the trading limit and in agreement with the Flag State, Classification Society, insurers and local authorities. Most ports will only grant a temporary permit to layup a vessel in this condition in port, provided that Class and Flag surveys are conducted. There may be local restrictions on vessels operations such as restrictions on the transfer of oily bilge water.
Cold layup (three-week reactivation)
Suitable for up to five years out of service. In this condition, vessel crewing is in line with emergency requirements to deal with fire, flooding, mooring and security watch. Cold ship layup locations are generally remote so access to the vessel can be limited. Upon reactivation, the vessel may need to go direct to dry dock before trading, depending on the extent of any hull marine growth. It is imperative that all preparations and processes during cold layup are well documented as crew changes may be significant.
Long-term layup (three-month reactivation)
Suitable for up to more than five years out of service. In this extended condition, preparations are comprehensive as original manufacturers are consulted for critical equipment, Any remedial work done on reactivation is likely to be extensive and unpredictable, such as renewal of alarm systems that may have become obsolete. For long-term layups, several vessel are laid up side-by-side to minimise supervision costs.
ASC is aware of all these potential problems involved in layups and has the experience, expertise and resources to avoid the pitfalls.
Preparation for layup of vessels
ASC can provide a range of specialist underwater maintenance, servicing and repair work on vessels as layup starts, throughout the layup period and at reactivation, including:
Hull cleaning - Ongoing research and development of new-generation hull cleaning equipment ensures understanding of how to successfully clean the latest low surface energy coatings currently in service.
Propeller polishing - A propeller-polishing tool can produce an industry standard surface finish of 0.5µ Ra. The cost of a quality underwater polish represents only a small proportion of the fuel savings it achieves.
Worldwide inwater surveys - Major Classification Approval ensure equipment is optimised to match the prevailing underwater conditions by using CCTV and high-resolution cameras that are sensitive to low light levels. ASC can also provide CAD generated drawings.
Other services include - Afloat Shell Plating - Repairs Allowing defective areas of shell plating beneath the waterline to be cut out and replacement insert plates be welded into position whilst the vessel is afloat.
Afloat Stern Seal Repairs - Capabilities to provide underwater stern seal replacement and repair services strategically situated at key global sites.
Afloat Propeller Repairs - Technically sophisticated solutions to propeller damage and associated performance problems in cooperation with Subsea Propeller Incorporated (SPI).
Underwater Welding - Typical Applications Sacrificial and impressed anode replacement, Rope guard and rudder repairs, External doubler plates, Sealing up disused inlet and outlet.
Specific services that may be required before, during and after layup include the following:
- In-water inspection of underwater hull and fittings prior to layup, with particular attention to the condition of the coating and the sacrificial anodes;
- Reinstatement of coatings underwater, such as epoxy anticorrosive coatings and (if required) tin free underwater applicable antifouling;
- Replacement of depleted sacrificial anodes and attachment of additional of sacrificial anodes for protection during layup (essential if impressed current systems are to be switched off).
- Design, manufacture and fitting of pressure blanks to sealing sea chest openings and discharge pipes while ship side valves are inspected internally, repaired or replaced. These pressure blanks are a sandwich of aluminium and marine plywood and thus unsuitable for long-term immersion. Information from ship’s drawings or a detailed inspection by divers is required to ensure the correct fit on the hull.
- For long-term layup, removal of valves to prevent corrosion and isolation of internal pipe work from sea water by fitting temporary steel spade blanks. Valve removal relieves the need for movement of the valves at regular intervals. Removal of valves and sealing the hull opening also removes the flooding risk where manhole doors are removed from salt water cooled coolers and equipment within the engine room;
- Fitting of layup sea chest covers to seal the sea chest against water flow and sunlight to limit fouling growth within the sealed sea chest. A capped port can be fitted for injection of biocide to kill off any existing fouling inside the sea chest, but full local permission is required before using biocides. Covers would not be applied to fire pump sea chests as they must be kept operational throughout layup.
- Periodic underwater inspections in line with class or owner requirements to monitor the hull condition and rectify emergent work;
- Monitoring of oil leakage and temporary sealing arrangements made where leakage found;
- Monitoring of bow and stern thrusters for leakage, as well as removal for repair ashore and reinstatement prior to re-commission;
- Regular hull cleaning. Vessels with biocide free low energy antifouling hull coating will foul rapidly while stationary. Unchecked, this may permanently damage;
- Sealing of emergent leakage problems caused by hull corrosion;
- Fitting pressure blanks to sea valves to allow repair and replacement;
- Underwater inspection of mooring / anchoring systems;
- Full Class inspection surveys, if required, depending on layup duration;
- Periodic checks on the hull electrical potential along the underwater side area to assess the effectiveness of the anode hull protection system.
- Hull cleaning prior to vessel leaving under her own power or being towed to a dry dock/breaker' yard;
- Removal of sea chest covers;
- Cleaning of fouling choked sea chests;
- Application of pressure blanks for reinstatement or inspection of hull side valves;
- Inspection of rudders and stabilisers prior to and during re-commissioning of the systems to ensure correct operation and rectification of any defects;
- Propeller polishing to remove fouling and calcareous deposits and peak efficiency of the propulsion system once the vessel gets under way;
- Underwater inspection by competent diver, as required by Class if layup period is more than 12 months.
All work carried out during layup preparation must be carefully recorded, documented and photographed. Copies of records should be retained on board (or ashore in designated office) during the layup period for use during reactivation. Any spares or equipment subsequently removed for operational purposes, such as transfer to other operational vessels, must be duly recorded. A daily routine log book must be kept to record all activities carried out by the layup team.
The nature and extent of preservation required for each laid-up vessel is determined by:
- layup duration.
- layup location and corresponding climatic conditions.
- general condition of the vessel (to be assessed and corrective maintenance performed in liaison with the owners prior to layup).
- conditions governing re-commissioning.
Corrosion is a major problem when laying-up a vessel and all measures should be made to reduce and even eradicate the risk. Any measures taken must be recorded for reference as a check list when the ship is re-commissioned. The following methods are used to reduce corrosion:
- Total and effective sealing of major accommodation and machinery spaces from external atmospheric conditions, particularly where high humidity levels exist.
- Controlled dehumidification of internal air spaces (including void spaces within machinery and pipelines) to prevent sweating and humidity corrosion damage, as well as moisture absorption into electrical cables and fittings.
- Application of preservatives and suitable lubricants to external equipment and machinery not within the dehumidified spaces.
- Hull cathodic protection to be maintained, and for long term layup ballast tanks to be suitably protected. This could mean that they are totally emptied, cleaned and dried out or fully ballasted to remove air pockets and corrosion inhibitor added.
- Regular turning of rotating machinery to prevent corrosion damage to bearings, seizure and component distortion. Equipment would be identified and highlighted on the check lists for this purpose.
Controlled humidity space sealing and dehumidification
Humidity can present risks for laid-up vessels. Corrosion and other moisture damage can be costly and cause serious delays when the time comes to re-activate. ASC provides a range of dehumidifying services to reduce the risk of such damage.
The atmosphere within designated spaces should be kept within certain set limits to ensure preservation of equipment. In some geographical location or during certain seasons, some may consider this to be unnecessary. However, this is a fallacy and dehumidification requirements should never be underestimated.
Main Machinery spaces should be maintained at 30 – 50% RH
Accommodation spaces should be maintained at 45 – 55% RH
All openings – including doors, windows, port holes, vent/extraction apertures, sanitary outlets, scuppers, drains and air intake grids – should be secured and sealed using proven methods. Limited means of access to be retained.
Dehumidification units of adequate capacity need to be sited and installed, together with associated distribution trunking to achieve sufficient air circulation both within the ‘controlled’ spaces as a whole and through major individual items of machinery, equipment and systems within those spaces. The circulation of dry air will be arranged such that desired levels of relative humidity will be achieved throughout. All water / steam systems and tanks within the controlled spaces, except those required for the layup operation will be drained free of water (including bilge areas), dried and left open to dehumidified atmosphere. Non-return valve internals will be removed where necessary to improve air circulation within the systems