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Ship Maintenance Requirement and Energy Efficiency Measures

International Safety Management Code (ISM) specifies the rules and regulations for maintenance management that influence the shipping industry. The ISM Code stipulates that each ship operator is responsible for the ship's safe and pollution-free operation. The ship's hull, machinery and equipment should be maintained and operated following applicable rules and regulations.

The part of the ISM Code on "maintenance of the ship and its equipment" describes in general how ships should be maintained, inspected, non-conformities be reported, and corrective actions are taken. Accordingly, the ISM Code states that the shipping company should establish procedures to ensure that the ship is maintained in conformity with the provisions of the relevant rules and regulations and with any additional requirements which may be established by the company. Based on the ISM Code, it is a requirement that "the company should identify equipment and technical systems that through sudden operational failure might result in hazardous situations."

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When implementing a maintenance management system on board a vessel as part of the shipping company's safety management system, it is imperative to define the critical systems and equipment. According to manufacturers or other policies, maintenance instructions should be issued to ensure the uninterrupted and safe operation of them.

On the same ship safety issue, the classification societies are a big player within their classification rules. The primary classification societies gradually support more advanced routines for non-intrusive inspections. These include condition-based maintenance where equipment and machinery systems can receive a specific class certificate of alternative survey arrangement if maintained according to this alternative method. This approach simplifies classification routines for certain specific shipboard equipment and systems, leading to more flexible operation and reduced inspection costs.

Maritime maintenance management

Like any other continuous improvement activity, the senior management has to be committed to providing required resources, competent crew, and a well designed and implemented a maintenance management system to achieve the above objectives onboard. The fundamental part of the maintenance management system is normally a database that contains a register of all equipment on board that needs to be maintained. This database then populated with maintenance plans, maintenance activities carried out, etc. thus providing not only the requirements and plans for maintenance but also the full history of maintenance activities performed.

Effective maintenance planning is essential for ship operation due to its complexity and the obligations on shipping organizations to comply with specific regulations and requirements, including ISM. Poor maintenance management could reduce the ship's availability, which may, in turn, be reflected in the revenue of the company. Another issue that requires attention is the impact of maintenance on the ship's fuel consumption that is highlighted in this section. It is argued and shown that proper maintenance leads to more energy-efficient ship operation. Thus the requirement for maintenance and energy-efficient operation fully overlaps with each other.

Type of maintenance

Maintenance has different forms, and its application may vary from one company to another depending on their diverse requirements. The shipping company usually chooses the most appropriate maintenance type for various ship's equipment based on its maintenance policy or strategy.

The figure indicates different maintenance types and policy options with an outline description that follows.

Unplanned Maintenance: This type of maintenance is basic and simple as it is defined as breakdown maintenance. In this maintenance policy, the repair or replacement is performed only when a failure occurs. In this type of maintenance policy, however, basic preventive maintenance routines such as lubrication and machine adjustment are applied to the system at regular intervals.

Planned Maintenance: Maintenance scheduling or planning embraces all activities necessary to plan, control, and record all maintenance activities. Planned maintenance is based on a defined schedule of equipment maintenance. This maintenance policy is the standard practice today in the majority of shipping companies. The planned maintenance schedule is decided based on manufacturers' recommendations or use of analytical techniques such as analysis of mean time between failures (MTBF) and reliability analysis. This approach is based on a model of the time that elapses between maintenance periods that takes into account the mechanisms of failures.

Therefore, the planned maintenance schedule is not necessarily based on fixed-time programs but could be based on an analysis method that considers several factors, such as the equipment's reliability characteristics. Preventive Maintenance: This is a subset of planned maintenance (see Figure 8.1). Preventive maintenance usually depends on the manufacturer‘s recommendations and past experience for scheduling repair or replacement time. In this policy, the maintenance is performed on a planned basis within normally fixed scheduled intervals. Preventive maintenance is thus time-driven in that maintenance is performed based on elapsed time or hours of operation.

The preventive planned maintenance is still the main strategy for shipboard maintenance. The intervals were based upon the manufacturers’ recommendations in addition to past company’s or ship-board experience.

Ship maintenance by location

Predictive Maintenance: This is a subset of planned maintenance (see Figure 8.1). This is generally based on what is referred to as condition-based maintenance (CBM) or reliability-based maintenance (RCM). The maintenance decision is based on the current condition or reliability of the system or equipment. This policy stipulates the monitoring of the machinery and acting upon its condition. Usually, engineers record the system parameters, do condition/performance analysis, and use their senses or equipment to hear, sight, and smell the equipment to assess the system's condition. Different techniques are used in condition monitoring, such as visual inspection, performance monitoring, trend monitoring, vibration monitoring, lubricant monitoring, thermograph monitoring, and acoustic monitoring. The advantages of such a policy are that unnecessary maintenance work can be avoided. In this way, the loss of production during scheduled machine downtime can be reduced, and components can remain in service if it is in good working condition. The industry is gradually moving from preventive maintenance to predictive maintenance.

Reliability Centred Maintenance (RCM): This could be regarded as a subset of predictive maintenance. RCM is a structured way to determine the maintenance requirements of complex systems and assets. It was first developed in the late 1960s, and the approach was derived from the aircraft industry. RCM focuses on the effect of failure with the consequences of a failure being more important than its technical characteristics. The main objective of RCM is to reduce the maintenance costs by focusing on the most important functions of the system and avoiding or removing maintenance actions that are not strictly necessary.

Corrective maintenance: The corrective maintenance may be defined as maintenance, carried out after failure detection. Corrective maintenance can be subdivided into "immediate corrective maintenance" (in which work starts immediately after a failure) and "deferred corrective maintenance" (in which work is delayed in conformance to a given set of maintenance rules). Corrective maintenance is thus a subset of the unplanned maintenance policy.

The ship maintenance and repair activities can be completed in two different ways.
  1. They can be undertaken in the ship repair yard when the ship is due for dry docking for regulatory or class surveys. Certain type of maintenance activities are carried out at shipyard when the ship is at berth.
  2. Maintenance can be conducted during the ship‘s day-to-day operations of the ship; either while at sea or when in port.
Figure 8.2 shows this way of dividing the maintenance and repair activities.
Types of maintenance policy

Prevention Of Pollution While Carrying Out Overboard Maintenance

Any overboard maintenance must be carried out only after taking permission from port authorities and taking due precautions to prevent any material from falling overboard. Many port authorities have pollution regulations restricting or forbid maintenance being carried out over the ship's side. This is due to the possibility of potentially damaging substances dropping into the water. Accordingly, Masters must check with the local agent to see what regulations are applicable before planning or carrying out any overboard maintenance. In ports where such maintenance is permitted, all possible precautions must be taken to avoid polluting the water with paint, thinners, chemical cleaners, loose scale, or other potential contaminants.

Maintenance and energy efficiency

Maintenance operations are fundamental for the energy-efficient operation of machinery and systems. Deterioration of ship systems' condition occurs due to normal wear and tear, fouling, mis-adjustments, long periods of operation outside design envelopes, etc. As a result, equipment downtime, quality problems, energy losses, safety hazards, or environmental pollution may results. The result is a negative impact on the operating cost, profitability, customer satisfaction, and probable environmental impacts if maintenance is not properly done.

The major challenge of maintenance optimization is implementing a maintenance policy that maximizes the equipment's availability and efficiency, controls the rate of equipment deterioration, ensures safe and environmentally friendly operation, and minimizes the total cost of the operation, including energy cost. Fortunately, most machinery maintenance activities are simple adjustments, cleaning, part replacement, or elimination of adverse conditions, which means preventive maintenance. Studies by various industries and companies have shown that a company can cut energy consumption at its facility by about 5% to 10% by focusing on its preventive maintenance effort [Terry Wireman 2011]. As indicated earlier, the main strategic aim of a maintenance program is to safeguard the ship's safety and assets and increase the ship's availability for the highest operational returns. Luckily, the excellent maintenance of a ship generally leads to improved performance of the hull, propeller, and machinery, thus providing a more energy-efficient operation.

Hull and propeller cleaning

The impact of hull or propeller fouling and roughness on may affect ship energy efficiency quite significantly. Thus keeping hull and propeller in clean good condition can lead to major energy saving.

Engines’ adjustments and tuning

Engines are the subject of frequent maintenance actions for various reasons; one of the main reasons is the impact of burning low-quality fuel and its impact on engines. Engine condition monitoring is normal practice onboard ship, and engine adjustments and tuning could lead to energy saving.

Mechanical transmission systems

Onboard ships, a variety of mechanical transmissions systems are used. The most complex and important one is the propulsion shafting, and the simpler ones include all the mechanical linkages between drives/motors and the machinery. The energy savings in automatic transmission systems would be influenced by the type of maintenance performed and adjustments made. For example, the following would influence the energy efficiency of the mechanical transmissions systems depending on the type: