CONDITION-BASED & RISK-BASED MAINTENANCE

 2.3. CONDITION-BASED & RISK-BASED MAINTENANCE   

By Aleksandar Pudar

Technical Superintendent and Planned Maintenance Supervisor Reederei Nord BV

Co-founder of "Out of Box Maritime Thinker Blog" and Founder of Naro Consilium Group

Condition-based maintenance (CBM) is a maintenance approach that involves monitoring the equipment's condition in real-time to detect and prevent possible failures. CBM uses various sensors and diagnostic tools to measure and analyse equipment operating conditions, such as temperature, vibration, and pressure and then makes maintenance decisions based on the equipment's current condition. CBM aims to detect and diagnose problems before they cause equipment failure or downtime.

Risk-based maintenance (RBM) is a strategy that prioritises maintenance activities based on the risk associated with equipment failure. It involves analysing the likelihood and consequences of equipment failure and selecting appropriate maintenance actions to mitigate the risks.

RBM is based on the idea that not all equipment failures are equally important, and some failures can significantly impact operations, safety, and the environment more than others. By focusing maintenance efforts on the most critical equipment and failure modes, RBM can help organisations optimise maintenance spending and improve equipment reliability.

CBM and RBM are two maintenance strategies that can work together effectively. CBM focuses on monitoring the condition of equipment to detect and diagnose potential problems, while RBM prioritises maintenance activities based on the risk associated with equipment failure.

In practice, CBM can provide valuable input to the RBM process by providing real-time data on the condition of the equipment. By continuously monitoring equipment and collecting data on performance, CBM can help identify equipment at a higher risk of failure and prioritise it for maintenance.

Conversely, RBM can help guide the CBM process by providing a framework for prioritising maintenance activities based on the risk associated with equipment failure. By identifying the most critical equipment and failure modes, RBM can help focus CBM efforts on the areas most needed, optimising maintenance spending and improving equipment reliability.

Overall, CBM and RBM are complementary maintenance strategies that can work together to provide a comprehensive approach to equipment maintenance. Organisations can minimise equipment failure, increase operational efficiency, and optimise maintenance spending by utilising real-time condition monitoring and a risk-based approach to maintenance planning.

2.3.1 CBM and RBM - Processes

Equipment maintenance can be approached in two distinct but complementary ways: CBM and RBM. The following is a brief overview of the steps involved in each process:

CBM Process:

·         Equipment Selection: Identify the critical equipment that requires monitoring and maintenance.

·         Sensor Deployment: Install sensors on the selected equipment to measure relevant operating parameters, such as temperature, vibration, and pressure.

·         Data Acquisition: Collect data from the sensors in real-time or at regular intervals.

·         Data Analysis: Analyse the collected data to identify patterns and trends, detect anomalies, and diagnose potential problems.

·         Maintenance Action: Take appropriate maintenance actions based on the results of the data analysis, including inspection, preventive maintenance, and corrective actions.

·         Continuous Improvement: Continuously monitor and evaluate the CBM program's effectiveness, and refine it as necessary to optimise equipment reliability.

RBM Process:

·         Risk Assessment: Identify and evaluate potential risks associated with equipment failure, including the likelihood and consequences of failure.

·         Failure Mode Analysis: Analyse the failure modes of the equipment and prioritise them based on their level of risk and criticality.

·         Maintenance Planning: Develop plans focusing on the most critical equipment and failure modes, including inspection, preventive maintenance, and corrective actions.

·         Implementation: Implement the maintenance plans, including scheduling maintenance activities and allocating resources.

·         Monitoring and Feedback: Continuously monitor equipment performance and adjust maintenance plans based on feedback received.

·         Continuous Improvement: Continuously monitor and evaluate the RBM program's effectiveness and refine it to optimise equipment reliability.

CBM and RBM are proactive maintenance strategies that optimise equipment reliability and reduce maintenance costs. CBM monitors equipment conditions in real time, while RBM prioritises maintenance activities based on the risk associated with equipment failure.

2.3.2 CBM and RBM - Vessel Management

The need for timely and factual data defining the operating condition of critical equipment and the effectiveness of operations such as maintenance and purchasing hinders the effective management of vessel machinery and equipment. CBM and RBM offer solutions to eliminate all factors limiting the performance of machinery and equipment. High maintenance costs directly result from inherent problems throughout the vessel, including poor design standards, outdated management methods, and improper operation, contributing more to high costs than catastrophic equipment failure.

However, the breakdown mentality and myopic view of the root cause of ineffective equipment/machinery performance can restrict vessel owners and operators to corrective maintenance functions or only use CBM and RBM as maintenance functions. Expanding the program to include regular evaluation of all factors that limit overall vessel performance can significantly enhance the benefits derived from CBM and RBM.

CBM and RBM are critical maintenance strategies for tankers and bulkers. These strategies can help eliminate factors limiting equipment and machinery performance, reduce maintenance costs, and enhance overall vessel performance by evaluating all contributing factors, not just those related to maintenance. Here are some detailed examples of how CBM and RBM can be implemented on a vessel:

2.3.2.1 CBM Management on a Vessel:

Example 1: Condition monitoring of a two-stroke Main Engine, such as the MAN ME engine

Engine condition monitoring is critical for ensuring safe and efficient vessel operation. CBM can monitor engine performance, detect potential problems, and prevent equipment failure. For example, one can install temperature and pressure sensors on the engine to keep track of coolant and oil temperatures and pressure. This data can be analysed to identify trends and patterns that indicate potential problems such as leaks, overheating, or worn components. Here is an example of how condition monitoring can be applied to the ME MAN two-stroke main engine:

·         Temperature Monitoring: Temperature sensors can be installed on various engine parts, such as cylinder liners, exhaust gas temperatures, and cooling water temperatures, to monitor the engine's thermal conditions. The collected temperature data can be analysed to identify abnormal temperature changes that may indicate potential issues such as overheating or cooling system blockages.

·         Vibration Monitoring: Vibration sensors can be installed on the engine's main bearing and other vital components to monitor vibration levels. The collected vibration data can be analysed to identify abnormal vibration patterns indicating potential issues such as bearing wear or misalignment.

·         Oil Analysis: Regular oil analysis can be conducted to monitor the engine's oil condition, such as the presence of metal particles, water, and other contaminants. The collected oil data can be analysed to identify any abnormal oil conditions indicating potential issues such as bearing wear or oil system contamination.

·         Pressure Monitoring: Pressure sensors can be installed on the engine's fuel and lubrication systems to monitor the pressure levels. The collected pressure data can be analysed to identify abnormal pressure changes indicating potential issues, such as fuel system blockages or lubrication system failure.

·         Exhaust Emissions Monitoring: Exhaust gas analysers can be installed to monitor the engine's exhaust emissions, such as NOx and SOx. The collected exhaust gas data can be analysed to identify any abnormal emissions indicating potential issues such as incomplete combustion or fuel system blockages.

Example 2: Steam-driven Cargo Pumps

Condition monitoring of steam-driven cargo pumps onboard tanker vessels is critical for ensuring safe and efficient cargo transfer operations. Here is an example of how condition monitoring can be applied to steam-driven cargo pumps:

·         Vibration Monitoring: Vibration sensors can be installed on the cargo pumps to monitor vibration levels. The collected vibration data can be analysed to identify abnormal vibration patterns indicating potential issues such as impeller damage, misalignment, or bearing wear.

·         Temperature Monitoring: Temperature sensors can be installed on the pump bearings and mechanical seals to monitoring the pump's thermal conditions. The collected temperature data can be analysed to identify any abnormal temperature changes that may indicate potential issues such as overheating or insufficient cooling.

·         Pressure Monitoring: Pressure sensors can be installed on the suction and discharge sides of the pump to monitor the pressure levels. The collected pressure data can be analysed to identify abnormal pressure changes indicating potential issues such as clogging or leaks.

·         Flow Monitoring: Flow meters can be installed on the suction and discharge sides of the pump to monitor the flow rates. The collected flow data can be analysed to identify abnormal changes indicating potential issues, such as blockages or worn impellers.

·         Steam Quality Monitoring: Steam quality meters can be installed to monitor the steam quality, such as pressure and temperature, to ensure that the steam-driven cargo pumps receive the required steam quality for their operation.

2.3.2.2 RBM Management on a Vessel:

Example 1: Environmental Risk Assessment - BWTS maintenance

Environmental risk assessment is critical for maintaining the Ballast Water Treatment System (BWTS) onboard tanker vessels. The BWTS is designed to prevent the spread of invasive species and other harmful organisms through the ballast water discharge. Here is an example of how environmental risk assessment can be applied in risk-based maintenance for the BWTS:

·         Identify the potential environmental risks: The first step is to identify the potential environmental risks associated with the BWTS operation, such as inadequate treatment, discharge of untreated ballast water, or discharge of residual biocides.

·         Assess the risks' likelihood and consequences: Each environmental risk's likelihood and consequences are assessed. For example, the likelihood of inadequate treatment can be assessed based on factors such as the system's design, age, and maintenance history. Likewise, the consequences of inadequate treatment can be assessed based on the potential impact on local ecosystems and aquatic life.

·         Prioritise the risks: The identified environmental risks are then prioritised based on their likelihood and consequences. For example, inadequate treatment may be considered a high-priority risk due to its high likelihood and severe consequences.

·         Develop a maintenance plan: Based on the prioritised risks, a maintenance plan is developed to address the most critical environmental risks. The plan may include regular inspections, maintenance, and testing of the BWTS to ensure it works effectively.

·         Implement the maintenance plan: The maintenance plan is implemented, including scheduling maintenance activities and allocating resources. For example, regular inspections and maintenance of the BWTS components may be scheduled, and the system's performance may be tested to ensure it meets the regulatory requirements.

·         Monitor and evaluate the plan: The maintenance plan's effectiveness is continuously monitored and evaluated, and adjustments are made as necessary to optimise environmental performance and reduce the risk of environmental pollution

By prioritising maintenance activities based on the risk level associated with environmental pollution, vessel operators can reduce the risk of invasive species transfer, comply with regulatory requirements, and ensure safe and sustainable operations.

Example 2: Safety Risk Assessment - Emergency Diesel Generator (EDG)

Safety is a critical consideration onboard vessels, and equipment failure can result in potential safety hazards for the crew and the vessel. RBM can identify equipment and systems with the most significant safety risks and prioritise maintenance activities accordingly. Here is an example of how safety risk assessment can be applied in risk-based maintenance for the Emergency Diesel Generator (EDG) onboard a tanker vessel:

·         Identify the potential safety risks: The first step is to identify the potential safety risks associated with the EDG operation, such as engine failure, fuel leaks, or exhaust system failure.

·         Assess the risks' likelihood and consequences: Each safety risk's likelihood and consequences are assessed. For example, it is important to consider the engine's age, operating conditions, and maintenance history to determine the likelihood of engine failure. In addition, it's crucial to assess the potential consequences of engine failure, considering how it could impact vessel safety and the ability to continue operations.

·         Prioritise the risks: The identified safety risks are then prioritised based on their likelihood and consequences. For example, the risk of engine failure may be considered a high-priority risk due to its high likelihood and severe consequences.

·         Develop a maintenance plan: Based on the prioritised risks, a maintenance plan is developed to first address the most critical safety risks. The plan may include regular inspections, maintenance, and testing of the EDG to ensure that it is working effectively.

·         Implement the maintenance plan: The maintenance plan is implemented, including scheduling maintenance activities and allocating resources. For example, regular inspections and maintenance of the EDG components may be scheduled, and the system's performance may be tested to ensure that it is meeting the regulatory requirements.

·         Monitor and evaluate the plan: The maintenance plan's effectiveness is continuously monitored and evaluated, and adjustments are made to optimise safety performance and reduce the risk of safety hazards.

By continuously monitoring equipment conditions and prioritising maintenance activities based on the risk level associated with equipment failure, vessel operators can optimise maintenance spending and reduce the risk of equipment failure, downtime, and costly repairs.

2.3.3. CBM and  RBM - Practical Techniques

Here are some practical techniques that can be used for CBM and RBM:

2.3.3.1 CBM Techniques:

·         Vibration Analysis: An effective method for CBM is vibration analysis. It entails measuring and examining vibration data from rotating machinery, such as turbines, motors, and pumps. The analysis can detect unusual vibration patterns that may signal potential problems, such as bearing wear, unbalance, or misalignment.

·         Thermography: Thermography is a CBM technique that uses infrared cameras to measure equipment temperatures such as electrical panels, motors, and bearings. The data is analysed to identify any abnormal temperature patterns that may indicate potential issues such as overheating or insufficient cooling.

·         Oil Analysis: Oil analysis is a CBM technique that involves regularly analysing the lubricating oil from equipment such as engines, gearboxes, and hydraulic systems. The oil is analysed to identify abnormal conditions, such as metal particles, water, or contaminants, that may indicate potential issues such as wear, contamination, or poor lubrication.

2.3.3.2 RBM Techniques:

·         Failure Modes and Effects Analysis (FMEA): FMEA is an RBM technique that involves identifying and analysing potential failure modes and their effects on equipment, processes, or systems. The data is used to prioritise maintenance activities based on the level of risk associated with each failure mode.

·         Root Cause Analysis (RCA): RCA is an RBM technique that involves identifying and analysing the root cause of equipment failures or incidents. The data is used to develop corrective actions that address the underlying causes of the failures or incidents rather than just addressing the symptoms.

·         Reliability Centered Maintenance (RCM): RCM is an RBM technique that analyses equipment function and performance to identify the necessary maintenance activities to ensure optimal performance and reliability. The data is used to develop plans that prioritise maintenance activities based on the risk associated with each equipment failure mode.

2.3.4 Benefits of CBM and RBM

Tanker vessels can significantly benefit from critical maintenance strategies such as CBM and RBM. These strategies can improve equipment reliability, reduce maintenance costs, enhance safety, comply with regulatory requirements, improve operational performance, and reduce environmental impact.

CBM and RBM enable early detection of equipment issues, allowing for timely maintenance activities to prevent equipment failure and extend equipment life. By prioritising maintenance activities based on the level of risk associated with equipment failures, vessel operators can optimise maintenance spending, reduce the frequency of unnecessary maintenance activities, and minimise unplanned maintenance costs.

CBM and RBM help identify potential safety hazards early, allowing timely corrective actions to mitigate risks and improve safety performance. Additionally, they ensure that equipment is maintained to the required standards and that maintenance activities are documented and tracked, helping vessel operators comply with regulatory requirements.

CBM and RBM improve operational performance by ensuring that equipment operates optimally, reduces downtime and delays, and improve vessel efficiency and productivity. Moreover, RBM prioritises maintenance activities based on the level of risk associated with environmental pollution, allowing for timely maintenance activities that can prevent environmental damage and reduce the risk of non-compliance with environmental regulations.

Implementing CBM and RBM on board tanker vessels can have numerous benefits, including improving equipment reliability, reducing maintenance costs, enhancing safety, compliance with regulatory requirements, improving operational performance, and reducing environmental impact.

 2.3.5 The variances between CBM and RBM maintenance tactics

The critical difference between CBM and RBM is the focus of the maintenance strategy. CBM focuses on monitoring equipment conditions and performing maintenance at the optimal time, while RBM focuses on prioritising maintenance activities based on the level of risk associated with equipment failure. CBM aims to reduce maintenance costs by preventing equipment failure, while RBM aims to optimise maintenance spending by focusing resources on critical equipment.

2.3.6 Conclusion

Tanker vessels, and all other vessels, can greatly benefit from critical maintenance strategies such as CBM and RBM.CBM and RBM allow vessel operators to detect equipment issues early, prioritise maintenance activities based on the level of risk associated with equipment failures, optimise maintenance spending, reduce maintenance costs, improve equipment reliability, enhance safety, comply with regulatory requirements, improve operational performance, and reduce environmental impact.

By implementing CBM and RBM, vessel operators can improve equipment performance and reliability, reduce maintenance expenses, and ensure that their vessels operate safely, efficiently, and sustainably. In addition, vessel operators can mitigate risks associated with equipment failures and environmental pollution, reducing the likelihood of incidents and ensuring compliance with regulatory requirements.

Overall, CBM and RBM are essential maintenance strategies that vessel operators should adopt to maximise the benefits of their investments, minimise risks, and ensure their tanker vessels' safe and efficient operation. By leveraging the practical techniques and examples outlined in this text, vessel operators can optimise their maintenance strategies and achieve operational and environmental goals.

 

References & Bibliography:

 

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Leoni, L., De Carlo, F., Paltrinieri, N., Sgarbossa, F. and BahooToroody, A. (2021). On risk-based maintenance: A comprehensive review of three approaches to track the impact of consequence modelling for predicting maintenance actions. Journal of Loss Prevention in the Process Industries, 72, p.104555. doi:https://doi.org/10.1016/j.jlp.2021.104555.

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www.reliableplant.com. (n.d.). Condition-based Maintenance (CBM) Explained | Reliable Plant. [online] Available at: https://www.reliableplant.com/condition-based-maintenance-31823. [Accessed 1 May 2023].

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Disclaimer:

Out of Box Maritime Thinker © by Naro Consilium Group 2022 and Aleksandar Pudar assumes no responsibility or liability for any errors or omissions in the content of this paper. The information in this paper is provided on an "as is" basis with no guarantees of completeness, accuracy, usefulness, or timeliness or of the results obtained from using this information. The ideas and strategies should never be used without first assessing your company's situation or system or consulting a consultancy professional. The content of this paper is intended to be used and must.