Marine Maintenance Concepts

Life Cycle Cost analysis conducted on various classes of ships have proved that the cost of the operation and maintenance of a ship can be approximately 50%  to 60% of its Life Cycle Cost.  Considering the fact the cost of ships are normally several millions or billions of dollars, it can be seen that the cost of maintenance is quite a significant amount in the annual budgets of the ship owners. Therefore various options are considered by the ship owners to reduce the maintenance cost without any major impact on the performance of the equipment and the operational availability of the ships. In addition proper maintenance of the ships are also necessary to reduce the risk of environmental pollution and to ensure safety of men and material at sea.MM

Some of the most common maintenance concepts followed by ship owners are as follows:

Reactive or Corrective Maintenance: Reactive or Corrective maintenance, also known as Break Down Maintenance is based on the policy of ‘Run Until It Breaks’. This is the most avoided kind of maintenance onboard ships as it poses a serious safety risk. In this case, no actions are carried out to maintain the  equipment and it is expected that the equipment will fulfill its design capability for the for the duration of its designed life. Reactive maintenance may at times prove to be cost effective type of maintenance through the life cycle of an equipment, provided the failure of the equipment does not lead to any major catastrophe. But considering the fact that most of the equipment onboard ships are critical, Reactive Maintenance is the least recommended mode of the maintenance of equipment onboard.

MM1

Preventive Maintenance: Preventive Maintenance or Scheduled Maintenance is the most common mode of maintenance followed onboard ships. This system reduces the malfunctioning of the equipments and thereby reducing the downtime. Preventive maintenance is a calendar based or running hour based maintenance concept which employs various scheduled offline testing methodologies to conduct periodic assessment of the system and thereafter carry out the maintenance activities as prescribed in the schedule. The detailed procedure and schedule for the preventive maintenance routines such as change of filters, insulation tests, lubrication etc.  are normally advised by the manufacturer and, if followed correctly, it ensures efficient running of the equipment resulting in reduced life cycle cost.

Predictive Maintenance: The Predictive Maintenance method analyses the causes, symptoms and effect relationship of the equipment’s performance to predict the requirement of any corrective actions. In the case of a Predictive Maintenance program the key values of the equipment are measured or monitored and the values obtained are compared with the standard set of values for the respective equipment to identify the deviations if any. The causes of the deviations found are thereafter analyzed to identify the maintenance routines to carried out normalize the equipment’s performance parameters.

Condition Based Maintenance: Condition Based Maintenance is the maintenance activity carried out based on the knowledge of the condition of an equipment obtained from routine or continuous monitoring. MT2Condition Based Maintenance is similar to the Predictive Maintenance but uses both online and offline test data to decide up on the requirement of maintenance to be carried out. In the case of Condition Based Maintenance, if the test results fall in the normal or acceptable range, the scheduled Preventive Maintenance may be skipped which shall reduce the maintenance effort and the associated costs. Application of a customized Condition Based Maintenance plans are now gaining wider acceptance in the shipping world with the classification societies such as DNV coming up with the standards which permit the inclusion of this maintenance methodology in the overall maintenance program of ships.

Several aspects of an equipment including its functionality and criticality are to be considered before deciding up on the maintenance program for each equipment. The choice of the maintenance strategy also varies based on the class and type of the ships. The criteria for deciding the maintenance program for a commercial ship is different from that of a military ship. Commercially available analysis tools such as the FMECA, RCM, RAMS may be used to support the selection of the maintenance strategy. The continuous quest of the ship owners for a safe and economical maintenance methodologies has led to the introduction of Reliability Centered Maintenance in which an optimized maintenance strategy is formulated through a combination of Preventive, Predictive and Condition Based Maintenance practices best suited for the particular equipment. The advancements in the engineering and technology have led to the development of more reliable and rugged marine equipments and the monitoring systems which have revolutionized the maintenance requirements and widened the scope for introduction of more efficient and frugal maintenance programs for ships in future.

Ship’s Life Cycle Cost

Ship’s Life Cycle Cost (LCC) is the total cost of ownership of a ship and its equipment including its  conception, acquisition, operation, maintenance, upgrade and decommissioning. LCC is normally calculated by summing up the cost estimates from inception to disposal or in other words cost estimates from cradle to grave. While LCC analysis is carried out for commercial ships to estimate the net profit and return of investments, in the case of Naval Ship Building it is mainly used to choose the most cost-effective options from all the options available. LCC is normally used in the corporate world as a management decision tool based on facts, money and time.

To understand and analyze the LCC of a marine platform, it is very important to understand the various stages of its life cycle from different perspectives. The stages of life of a marine platform based on a shipbuilder’s perspective  would be Conception, Design, Engineering & Development, Production and Logistics Support. From a customer’s perspective the stages of life of a marine platform are Purchase, Operation, Support, Maintenance and Disposal.

Life Cycle Cost of a ship can be divided in to two parts – the initial cost or the acquisition cost and the future cost or the sustaining cost. The initial cost is the incurred prior to the purchasing of the ship and the future cost is the cost incurred after the commissioning of the ship.

LCC IB

In the case of marine platforms, especially the Naval ships, it is seen that the acquisition cost is approximately about 20% – 40% of LCC whereas the sustaining cost would be about 60% – 80% of LCC.

The LCC of Naval ships are normally reduced by the application of the Integrated Logistics Support (ILS) principles. LCC PIEThe costs are normally estimated based on the predictive method where no historic data are available or a method based on statistical data available for the existing systems. In all cases, appropriate discount rate and escalation rates are incorporated in to the calculations to make the future cost comparable with the present cost.

The success of any business depends on the application of a combination of good engineering practices and sound economic decisions. LCC analysis acts as a data based decision-making tool which can potentially provide comprehensive cost information that takes in to consideration a number of factors and brings out the hidden costs, thereby playing a decisive role in capital-intensive programs like ship building. However it should be noted that LCC does not provide an exact value of cost. As it is an estimate, the accuracy of LCC depends up on the correctness of  inputs and the method adopted for calculations. Notwithstanding this vital assumption, the LCC definitely provides an insight in to the cost factors and the magnitude of the associated costs which are critical for decision-making.

Cost and Schedule Overrun in Naval Shipbuilding

Naval Shipbuilding is a multi-billion dollar industry which deals with high-end and complex technology which demands high level of professional competence in Engineering and Management. Majority of the Naval Shipbuilding and Ship Refit programs have been affected by cost and schedule overruns due to various reasons, some of which shall be discussed in this article. A quick glance through the fact sheets of few of the prestigious Naval ship Building programs of major Naval powers, in some of the best shipyards across the globe, is sufficient to understand the gravity of this problem and its impact on the financial and military standings of the respective countries.

Unlike Commercial Shipbuilding and Ship Refit which are structured and standardized to a great extent, the Naval Shipbuilding and Ship Refit programs on most of the occasions are highly ambitious and more often than not deals with the introduction of new designs and technologies. Naval programs which are characterized by complex systems to cater for the challenging mission requirements coupled with a cost and schedule budget with little margin for error, increases the risk of cost and schedule overruns , especially in the case of first-in-class vessels of the program, which in turn may induce overruns due to knock on effect on the budget of follow on ships.

Some of the most important factors which cause cost and schedule overrun in Naval Shipbuilding and Ship Repair are as follows:

Design Finalization: Most of the ShipBuilding contracts are finalized without freezing the final design. Due to the typical nature of the industry, it normally takes a decade or more to develop a new class of ship from concept design to the delivery. This long duration of the Shipbuilding program makes it almost impossible to finalize on the technologies to be used as the life cycle of the technologies are much shorter. Therefore it becomes necessary to finalize the shipbuilding contract without detailed design. Moreover the detailed design process itself is a time-consuming and cost intensive activity which forces the concerned parties to conclude the contracts without investing on detailed design. This leads to formulation of contracts which are not very well-defined and which in turn leads to poor cost and time management as the program progresses. This ambiguity in the design of the ship is one of the major factors of cost and schedule overrun and therefore effort should be made to firm up the design, at the earliest, to the best possible extend with adequate provision for technological conversions.

Contracts and Cost Estimate: Normally there are two major types of contracts which are practiced in shipbuilding industry – Fixed Price Contracts and Cost Reimbursement Contracts. Provisions for conditional penalties for delay are incorporated in both the types of contract. In the case of Fixed Price Contracts, which are normally used for the follow on ships, the price is finalized and agreed by the ship builder and the client, and in the event of cost exceeding the agreed value; the additional cost is borne by the builder, unless the reason for it is attributable to the requirements of the client. In the case of Cost Reimbursement Contracts, which are normally used for the first-in-class ships, provision exists for the client to pay for all the additional expenses for completing the program, if the ship builder could justify the costs incurred.  Both the types of contracts sometimes include an incentive scheme which acts as a basis to control the cost and profit and encourage the shipbuilder and the client to perform their role more efficiently. As these contracts are based on the estimated costs, the accuracy of the estimate plays a major role in determining the probability of occurrence of any cost overruns. The terms and conditions handling any cost and schedule overruns must be well-defined in the contract for the benefit of all the stakeholders and to ensure the success of the program.

Complexity of the Systems: Highly advanced and complex systems chosen for Combat Management and Platform Management onboard often tend to increase the risk of Cost and Schedule overrun. The probabilities of occurrence of such overruns are at the maximum if the systems being selected are in the development stages. While such advanced systems under development are required to be chosen on some occasions to meet the mission capabilities of the vessel, adequate risk mitigation plans together with necessary provisions to meet any contingencies must be incorporated in the program.

Labor and Material Costs: The cost of labor and material for shipbuilding and ship repair constitutes a major portion of the program cost. The shipbuilding programs are normally spread across many years and therefore the effect of any escalation on the quantity of labor required or the increase in the cost of material pose a significant risk of cost and schedule overruns. The additional requirement of labor which may delay the project arises due to the rework s caused by immature design. Cost may also increase due to the overhead expenses such as the yard’s operational expenses which increase with the increase in duration of the program.

Engineering Changes: Major and Minor Engineering Changes warranted by regulations, or those initiated by the yard on its own initiative or the ones carried out due to client requirement, are found to be one of the major causes of the schedule delays. While the cost aspect is taken care in most of the cases, the amount of labor and time required to implement the changes may force a change in the program schedule resulting in the delayed delivery of the vessel.

Customer Factor: A demanding customer who always look for more value at no extra is a major cause for the scope creep which can result in cost and schedule overruns. Good communication and understanding with the customer is necessary for the smooth progress of the project. For example the cooperation of the customer is necessary for timely completion of the inspection activities and it is expected that the customer nominates competent personnel for such activities in time. At the same time the yard must provide all the required information towards this in advance to the customer in order to ensure that he comes prepared for the tests and trials.

Delivery of Materials and Services: The delay in delivery of the Materials and Services may cause schedule overrun in Ship building projects which can indirectly lead to the escalation of overall cost. For example the delay in delivery of the Engines could hold up the progress of structural work which may have a knock on effect on the other scheduled tasks. Similarly the delay caused due to the poor services provided by an incompetent sub-contractor can lead to quality issues delaying the acceptance of the vessel and thereby causing a schedule overrun for the entire program.

Project Management: Poor Project Management not only damages the reputation of the shipbuilder but also causes significant cost and schedule overruns. It is therefore very important for the Project Manager to understand the factors responsible for the overruns and adequate measures should be implemented proactively to avoid any cost escalation or schedule delay.

Funding Issues: Naval Shipbuilding and Ship Refit programs are mostly very expensive evolutions with a duration spread across many years and costing millions of dollars to the state.  Due to this reason the funds for the program are allocated in the budget by the governments of the respective navies in parts which are associated with various milestones of the program. Due to factors such as recession and economic crisis, which are now a common phenomenon in the world economy, the governments may be forced to restrict the funds for certain programs to meet other urgent requirements, thereby leading to a schedule overrun.

Technology Transfer: In the modern era of ship building, most of the navies are promoting indigenization which has led to the formation of strategic partnerships between the shipyards across the world. Such a partnership demands the transfer of technology which needs to be carried out in a controlled manner based on well-defined procedures.  Poorly controlled transfer procedures and lack of cooperation among the participating yards during various stages of the project may lead to cost escalation and unwanted delay in the completion of the shipbuilding program.

These are only few of the several factors which lead to Cost and Schedule overruns in Shipbuilding and Ship Refit programs. The very nature of the warship building program and its complexity makes it more prone to the risk of such overruns. All shipbuilding and ship refit programs demands high level of professional competence and strict project management. Overruns have happened in projects executed by the best of the yards for the best of the navies in spite of their vast experience and domain knowledge. Efforts should be made to identify well in advance the risk factors which can lead to cost and schedule overruns and have efficient plans in place to mitigate them. In addition, efficient project management practices are to be adopted to guarantee sufficient control of the cost and schedule at all stages of Shipbuilding or Ship Refit.

Marine Power System Design Documentation

One of the most critical part of the ship design is the design of the Ship’s Electrical Power Generation and Distribution System. The introduction of many new products and the advancement of technology in this field have made the design of Ship’s Electrical Power System very complex and challenging. As in the case of any aspect of ship design, the design of Ship’s Electrical Power System is also determined by the design rules defined by the classification societies. The rules of the Classification Societies for design, construction, installation or inspection of electrical equipment for ships are predominantly based on internationally accepted standards such as IEC 60092 and IEEE SA 45 and the implementation of these rules includes a number of processes during all stages of ship construction.

The design of the Ship is approved by the Classification Society by validating the system design documents which are required to be submitted by the ship’s designer/builder and these documents are categorized as ‘for approval’, ‘for information’ and ‘on request’  . Important Ship’s Electrical Power System design documentation which needs to be submitted for the approval/information/on-request  of the Classification Society (DNV as reference) are as follows:

  • Overall Single Line Diagram: The overall Single Line Diagram (SLD) is required to be approved by the Classification Society. It is a diagrammatic representation of the Ship’s Power System depicting the Generators, Transformers, Main and Auxiliary Switch Boards, Converters, MCCs Battery Systems and major  consumers. All the important system specifications are to be mentioned in the overall SLD.
  • Switchboard Single Line Diagrams: In addition to the overall SLD it is also required to produce the SLDs for each switchboard for AC, DC and UPS power distribution.  These drawings should have the details and ratings of the feeders including the interconnectors, cable dimensions and the settings of respective protective devices.
  • Electrical Consumption Balance: The purpose of this document is to study the consumption of the available power during various modes of operation of the ship such as Normal operation, Maneuvering, Combat operations, DP operations, Heavy Duty Crane operations, Cargo Handling, Normal Harbor operations etc. This document is normally produced in a tabular form stating the calculated design values of power consumption of each consumer under various modes of operation. The tripping of non-important consumers shall be determined based on this information and the Power Management System can be programmed accordingly.
  • Power System Philosophy: This document is submitted for the information of Classification Society and it explains the basic philosophy of the Ship’s Power System under various modes of operation. It will also have the details of the functionality of system/sub-system/consumer for automatic operation of the circuit breakers, Power Management System, Dead Ship Recovery, Emergency Power arrangements, Black-Out Recovery, etc.
  • Short Circuit Calculation: The Short Circuit Study or Fault Study is carried out to correctly size the buses, protective equipment and the cables. Preliminary short circuit calculation can be carried out once the load analysis and the number and ratings of the generators are determined. The calculation of Short Circuit Current is based on IEC 61363  and IEC 60909 and the study is conducted by calculating the symmetrical (RMS) and asymmetrical fault (Peak) currents using various methods such as MVA Method or Per Unit Method.
  • Harmonics Distortion Calculation: A Harmonics study is to be conducted if more than 20% of the connected load are constituted by semi-conductor assemblies such as Variable Speed Drives/ Static Frequency Converters. These semi-conductor assemblies produces harmonic currents which distort the ship’s power supply and causes damage to the electrical equipment. The Classification Society therefore insists the Total Harmonic Distortion of the voltage waveform for the overall power system shall not exceed 5% and it is required to submit the calculations/study document to the Classification Society with the details of the same.
  • Voltage Drop Calculations: As per the classification society rules the voltage drop at the terminals of the generator when a sudden load, such as a motor, is switched on, should not be more than 15%. A voltage drop more than the acceptable limit may cause malfunctioning of other electrical/electronic equipments in the system and may even activate the tripping of under voltage protection devices. A study is required be carried out to calculate the effect of starting of the largest motor load on the power system voltage and the documentation of the same is to be submitted to the Classification Society for their approval.
  • Discrimination Analysis:  The Discrimination Analysis also known as Protection Coordination Study is to be carried out to determine the settings for the protective devices (circuit-breakers and relays) which would reduce damage to equipment and to isolate only the circuit that has a short circuit or fault thereby causing minimum disturbance to the rest of the power system.  These studies also verify the correct fuse size and determine the protection required for conductors, transformers, and other equipment. The protection settings of each equipment is to be set primarily based on its individual characteristics and thereafter necessary coordination setting is to be done with respect to the reminder of the power system.

In addition to the above, other design documentations such as Failure Mode Effect Analysis (FMEA), Test Procedures (HATS & SATS), Electrical Schematic Drawings,  Cable Selection  Philosophy etc. are also required to be prepared and submitted to the Classification Society as a part of the design approval process for a Ship’s Electrical Power System. It should be noted that the Ship Design is an iterative process, especially the Ship’s Electrical Power System design and therefore several revisions of the design documents may be required to be produced for the design approval. The preparation of these documents normally involve power system studies which can be easily carried out by using application softwares such as ETAP, EDSA, Captor/ Dapper etc. It is always advisable to have strict version and quality control measures in place to ensure the accuracy of the data and documentation produced for the design and analysis of Ship’s Systems in general and the Power Systems in particular.

Electrical Propulsion for Naval Ships

The successful commissioning of Type 45 Destroyers not only marked a significant landmark in the evolution of Naval Power & Propulsion systems but also proved to the world that Integrated Electrical Propulsion (IEP) is the future of World Navies. The fact that IEP is the chosen mode of propulsion for the prestigious DDG100 Destroyers program of US Navy and the Queen Elizabeth Class (CVF) Aircraft Carrier program of Royal Navy underlines the significance of this technology in warship building. Electrical Propulsion with military specific advantages such as tactical endurance, increased stealth, increased redundancy and survivability, is definitely going to be an essential feature of naval capabilities and the key to naval transformation.

Mechanical Vs. Electrical Propulsion : In the case of Mechanical propulsion there are two sets of engines of which one is exclusively used for propulsion and the other is for generating electrical power for the electrically operated systems onboard. The high rpm of propulsion engine is converted to low rpm using a set of gears connected through a mechanical drive system.  In the case of Electrical propulsion there is a single set of engines connected to alternators to generate the electrical power which is used to run the heavy duty propulsion motors connected through Variable Speed Drives (VSDs) as well as to feed the electrically operated systems onboard.

Some of the important advantages of IEP are as follows:

Increased Stealth: Stealth is the most important aspect of any warship. It has been proved that the sound signature of the IEP vessels are considerably lower than that of the mechanically driven vessels. This reduces the warships overall acoustic detectability  which is very critical especially for the submarines and thereby increase their survivability and effectiveness. The reduction in the overall volume of the electrically propelled surface ships reduces their IR signatures and Radar cross section.

Reduced Life-Cycle Cost: It is estimated that an IEP warship will consume 10% to 25% less fuel than a similar ship with mechanical propulsion system. This would result in reduced life-cycle cost over the life of the vessel which normally is around 30 years. In addition to the savings on fuel, the IEP will also reduce the life-cycle cost as it would require less crew to man the vessel and as the maintenance requirement for the IEP is considerably lesser than the requirements of a conventional propulsion system.

Increased Survivability: By eliminating the requirement to fit all the equipments required for propulsion in a straight line along the bottom of the ship and permitting them to be placed in locations which can be better protected, the IEP improves the survivability of the warship to a great extent. The use of Electric Drive makes it possible to distribute the equipments around the ship and thus preventing a total failure of the propulsion system due to a single hit. The IEP also offers more flexibility in utilization of the available power during emergencies when more power would be required for operating damage control equipments or for preventing an imminent threat.

Flexibility for Power Utilization: The integrated electrical power system gives the flexibility to choose how to distribute the total energy available onboard to meet the propulsion, pay load and sensor load for various tactical situations. As the power required for propulsion can be controlled at any point of time, ships with IEP gives the advantage of fitting state of art and highly potent combat systems which would require large amount of electrical power for their operation.

Increased Payload: As the Electrically Propelled vessel is more fuel efficient, the requirement of space onboard for storage of fuel will be less compared to the conventional vessels. The elimination of shaft line and reduction gears would further reduce the overall space requirement for the propulsion system. This freed up space can be utilized to carry more payload which would increase the potent power of the warship.

Electrical Propulsion is an environment friendly technology which has been successfully used in  the commercial ships with huge tonnage and the technology in this area, even though constantly evolving, guarantees the required stability and life-cycle support. This is in contrast to the difficulties envisaged in the life cycle support of mechanical drive systems as most of its manufacturers have reduced the production of their components due to the shift of commercial shipbuilding towards Electrical Propulsion. The transition of Naval platforms to IEP will not only grant the advantages listed above but also give the opportunity for warship builders to take the advantage of the phenomenal technological advancements in the larger commercial electrical power conversion industry.

While the Electrical Propulsion technology offers many advantages, it also have some disadvantages like the high installation and near term costs, increased system complexity and less efficiency at full power. The past few years have been very important for the establishment of the IEP system in the naval environment.  Over the years Electrical Propulsion has been successfully implemented in several naval platforms like the LPD and Auxiliary Oilers of Royal Navy and the LHDs of French Navy. A land based Electric Ship Test Demonstrator (ESTD) was set up by Alstom for UK and France to test the current, future and emerging electrical propulsion technologies there by de-risking the future naval IEP platforms.  Many new researches are underway and the size of IEP equipments are expected to reduce significantly thereby offering strategic advantage of high power availability coupled with availability of more space onboard for combat systems.  With the significant operational and tactical advantages offered by this technology compared to the very few disadvantages, IEP is definitely the future of Naval Power and Propulsion. This is precisely the reason why major naval powers like the United States and the United Kingdom have chosen the IEP technology for their future warship plans.

Next Newer Entries