Neil Graham, technical director of diesel power company Royston, looks at the engineering and technical factors associated with bringing laid-up OSV engines back into service
Neil Graham, technical director of diesel power company Royston, looks at the engineering and technical factors associated with bringing laid-up OSV engines back into service
Reports of increased offshore investment and a growth in seismic exploration activity have provided some grounds for cautious optimism among OSV operators – and this supports a growing number of enquiries that UK-based Royston Ltd has received from vessel owners seeking advice and assistance in reactivating vessels ahead of anticipated new contract and tender opportunities.
Over many lean years within the offshore services sector there have been many hundreds of vessels that have been laid-up, with one recent study quoting the figure at over 1,700, or around 35% of the total fleet.
The reactivation of these vessels is not straightforward and inevitably requires a balanced consideration of the costs involved against the likely rates of return.
Neil Graham (Royston): “Bringing a vessel out of a long cold lay-up inevitably includes the risk of operational problems with engine function”
Fey to this process are the engineering and technical aspects associated with bringing a vessel’s engines out of a long-term lay-up period and giving due consideration to the maintenance and inspection procedures carried out during the lay-up.
Laid-up vessels are normally maintained in class. However, if the lay-up period is extended beyond the due date for special survey, the notation ‘Laid-up Surveys Overdue’ can be assigned and a minimum number of surveys agreed with the class society concerned. Complete suspension of class will normally invoke a termination of insurance cover. Class may also require a state of preserved or dry preserved engine.
Before a vessel can resume normal service, all overdue class and statutory surveys will need to be completed. In this respect, an accurate lay-up log is an essential requirement detailing the scope of any engine maintenance or service work carried out during the shutdown period. In addition, associated documents, such as dry dock work lists and lay-up personnel hand over reports, also provide useful documentation in terms of planning the engine reactivation measures required.
Accurate running hours for machinery should be made available throughout the lay-up period in order that appropriate spares for the maintenance of machinery items at reactivation can be planned by the joining crew and any attending technicians. In planning any maintenance works, careful consideration will need to be made of original equipment manufacturer (OEM) lead times for spare parts.
Full consideration of the lay-up reports and log books should enable a formal reactivation plan to be developed to restore the engineroom machinery and power systems to full working order. As part of this, any planned maintenance and service tasks that have been missed during lay-up periods will need to be checked.
Planning for reactivation
Planning for reactivation should of course commence when vessels are first laid-up. Decisions taken around hot or cold lay-up situations – or maybe something in between – will ultimately determine the steps needed to re-introduce a vessel back into service.
Bringing a vessel out of a long cold lay-up inevitably includes the risk of operational problems with engine function or performance and unplanned consequences that can extend the times and costs associated with any return to work.
“The reactivation of these vessels is not straightforward and inevitably requires a balanced consideration of the costs involved against the likely rates of return”
In theory, the reactivation of a ‘hot lay-up’ vessel should be more straightforward, but it is inevitable that owners will often have applied different levels of maintenance, technical attention and understanding to meet different class or flag state requirements while the vessel remained out of operation.
Determining the reactivation of any OSV therefore depends largely on the preparations made for lay-up – or lack of them – and the engineering and maintenance approach taken during out-of-service periods.
In particular, from an engineering perspective, there are a number of fundamental factors that need to be taken into account that can significantly influence the chances of the orderly return of a vessel to normal operation.
Any preservation measures taken should always reflect the prevailing environmental conditions, for example, appropriate action should be taken to prevent any damage due to freezing.
Engine damage
The risks of engine, component and associated system damage during lay-ups are many and varied and include the potential for corrosion, spalling, fractures, abrasive wear, adhesive wear, porosities, seizure, fretting and cavitation.
An example often encountered is the effect of adhesive wear between a bearing shell and a crankshaft journal during the starting or slow turning of an engine during a lay-up period. This is one of a number of potential engine problems that needs to be identified before a return to service. Other regular problems encountered are rust and scale in pipeline systems, dirty lube oil in engine oil bores, and problems with sticking cylinder head and air start valves.
The possible deterioration of the lubricating oils and fuel oils during the lay-up period also requires proper consideration. Lubricants and fuels are normally hydrocarbon-based products that are subject to degradation and contamination over time, which poses a risk to the efficient and safe operation of engine parts.
Routine checking and testing of all lubricating and fuel fluids should therefore be undertaken ahead of any propulsion and generator system reactivation work, including the inspection, cleaning and renewal where required of all cartridge and centrifugal filters.
The impact of the presence of moisture and any impact on engine parts is another area of concern and the review of any dehumidification records during lay-up can also provide a pointer to the likely risks of corrosion-related problems. For example, any areas of the engine that have condensation markings or where the records indicate that dehumidification has not been effective will require more care.
Note that for any lay-up other than a hot lay-up, the engines should be preserved/dry preserved as per class recommendations.
Seawater, fresh water and compressed air lines all require attention before, during and after the lay-up period to avoid problems relating to corrosion, scale build-up and blockages due to sediment.
Engines and associated systems
It is assumed that if the engines have been in cold lay-up, major overhauls (complete or partial to satisfy surveyors and maintenance requirements) will be conducted, and therefore tasks such as flushing through oil galleries will be done when the engine has had bearings removed.
With regards to the main engines, the current advice from engine manufacturers is for main engine crankcase spaces to be closed up and dehumidified during lay-up. However, this is not always the case and the recommended course of action is for a full crankcase inspection to be carried out, alongside checking the condition and security of rotating parts. In particular the need is to ensure that no foreign objects may have inadvertently been left behind and that there has been no condensation damage, bacterial growth or other contamination within the engine and sump.
The pistons and cylinder liners should be protected with an inhibitor and regular crankcase inspections carried out to check the general condition of engine internal components.
Blanking off of the exhaust gas system and air intakes is recommended to prevent moisture ingress into the engine.
For the lube oil system, consider blanking off or disconnecting the vent lines in the engineroom. The lube oil pumps and priming pumps should be turned on a regular basis and run up prior to starting the engine. Purifiers should be run up to clean the oil as much as possible, with samples taken for analysis before starting the engines.
Ideally, the lube oil system should be flushed through with a recommended flushing oil prior to starting the lube oil pumps.
Fuel lines with residual fuels should be drained and flushed with marine gas oil prior to lay-up. Any fuel remaining on board should be regularly tested for water, sediment, abrasives and microbial activity in the case of distillates. Water in fuel tanks should be drained off on a regular basis.
Fuel injection valves should also be cleaned, adjusted and refitted, and this requirement often applies to the fuel pumps also. The engine fuel system should be circulated prior to engine starting to ensure there is no leakage.
It is recommended that the starting air system is drained and opened up, cleaned and left dry. It is vital that any machinery or pipeline system that is left open should be subjected to a dehumidified atmosphere in the engineroom. Starting air valves should be removed and tested prior to start up.
Note that the engineroom temperature should always be a few degrees higher than the outside ambient temperature and never below freezing point.
Seawater systems, including pipelines and heat exchangers, should be opened and drained of water. The heat exchangers should be flushed with fresh water before being cleaned. If possible, leave the seawater system open to benefit from the dehumidified air.
Fresh water systems can be left filled if the appropriate chemicals are added and regularly tested to prevent corrosion and settling of solids.
“Lubricants and fuels are normally hydrocarbon-based products that are subject to degradation and contamination over time”
In general, all system valves should have their spindles greased and the valves operated regularly to prevent seizure. This also applies to seawater inlet valves, but a blanking off of the seawater system must take place to prevent seawater ingress.
The engines should be rotated regularly, and the shafts should be returned to a different position each time.
A vessel’s auxiliary diesel engines may have required an overhaul at the time of going into lay-up. This is particularly the case if they had been run at low loads for months during any period of interim hot lay-up without appropriate maintenance being carried out or running hour logs properly kept. It is therefore important that these items of machinery are also carefully examined as part of the reactivation process.
If the auxiliary engines have not been run during the lay-up period, a sample of main bearings and connecting rod bottom end bearings should be opened for examination, with possible remedial attention being dependent upon the condition found.
On completion of the various commissioning tasks that are undertaken after all checks and maintenance activities have been completed, full load engine and generator tests will be necessary to fulfil the requirements of the owner and the class surveyor.
The downturn in the OSV market finally appears to have turned a corner. In response, owners and operators who plan to reactivate their hot- or cold-stacked vessels need to think carefully about how this can be best achieved.
The danger is that rushing vessels back into service without the proper technical approach and attention to detail will lead to further problems – greatly undermining those brighter market prospects that have taken so long to emerge.
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