Introduction
Measure maintenance performance
When critical equipment breaks down, it costs you. Operational delays, unplanned maintenance costs, off-hire periods, and increased pressure on crews and shore-based teams. That is why measuring maintenance performance matters. The right metrics show how frequently equipment fails, how long repairs take, and how breakdowns affect operational readiness. Combined with maintenance histories and cost data, they can also help technical teams identify where operational losses occur.
The basics
What are MTBF, MTTR, and availability?
Mean Time Between Failures (MTBF), Mean Time To Repair (MTTR), and availability are three of the most widely used maintenance KPIs. Each metric provides useful information on its own, but they are most valuable when used together to evaluate asset performance and improve maintenance planning.
Mean Time Between Failures (MTBF)
MTBF measures the average operating time between failures of a repairable asset. It indicates equipment reliability: a higher MTBF generally means that the equipment fails less frequently. However, MTBF is an average time and does not predict exactly when the next failure will occur.
MTBF = Total operating time ÷ Number of failures
- Calculation example
A ballast pump operates for 2,400 hours and experiences six failures:
MTBF =
2,400 hours
6 failures
= 400 hours
The calculation is only meaningful when failures are defined and recorded consistently. Comparisons should also involve equivalent assets operating under reasonably similar conditions.
Mean Time To Repair (MTTR)
MTTR measures the average time required to restore equipment after failure. It reflects how efficiently the problem is diagnosed, the repair is completed, the equipment is tested, and it is returned to service. A lower MTTR generally means less downtime.
MTTR = Total repair time ÷ Number of repairs
- Calculation example
For example, six repairs on a ballast pump require a combined 30 hours:
MTTR =
6 Repairs
30 Hours
= 5 hours
MTTR is not always defined in the same way. Some include only active diagnosis and repair time, while others include waiting for spare parts, vendor support, testing, and other logistical delays. To compare MTTR across a fleet, define clearly when the measurement starts, when it ends, and which delays it includes.
Availability
MTTR measures the average time required to restore equipment after failure. It reflects how efficiently the problem is diagnosed, the repair is completed, the equipment is tested, and it is returned to service. A lower MTTR generally means less downtime.
Availability = MTBF ÷ (MTBF + MTTR) × 100
- Calculation example
This example uses the calculations from the two previous MTBF and MTTR balast pump examples
Availability =
400 Hours
400 Hours + 5 hours
x 100
= 98.8% Availability
A longer MTBF or shorter MTTR improves estimated availability. Measured operational availability may also include planned maintenance, logistical delays, administrative delays, and other sources of downtime, depending on how you define the KPI.
MTBF in practice
Applying MTBF in maritime maintenance
By tracking MTBF, technical teams can identify equipment that reduces operational reliability and investigate recurring failure patterns.
This means you can use MTBF to:
- Identify recurring failures. A low or declining MTBF signals a need to investigate root causes rather than repeatedly fixing symptoms.
- Compare sister vessels. Differences in MTBF can highlight issues when equipment, operating conditions, and reporting are comparable.
- Support criticality assessments. Low MTBF has greater impact on critical systems like engines or generators, especially where redundancy is limited.
- Review maintenance intervals. Repeated failures before scheduled maintenance may indicate issues with scope, conditions, or maintenance quality.
- Improve spare-parts planning. Failure history helps determine onboard stock needs, considering lead times, criticality, cost, and risk of stock-outs.
Linking spare parts to components and maintenance activities can also improve planning and reduce delays caused by unavailable inventory.
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Get control with Inventory Management
SERTICA helps you keep track of your inventory, so you always know if the spares are in stock, and helps your procurement department know when to reorder
MTTR in practice
Using MTTR to improve maintenance efficiency
Where MTBF shows how frequently equipment fails, MTTR shows how quickly the organization restores it. You cannot prevent every failure, but you can often reduce the time an asset remains unavailable.
A high MTTR should prompt technical teams to investigate what delayed the restoration:
- Were the required spare parts on board?
- Did the crew have the necessary competence and equipment-specific knowledge?
- Were maintenance procedures and technical documents clear and accessible?
- Was the work order prepared in advance, or created reactively after the failure?
- How quickly did the vendor or technical support provider respond?
- Did testing or approval requirements delay the return to service?
Improving work preparation, documentation, spare-parts availability, and fault diagnosis can reduce MTTR and improve availability, even when failures still occur.
Read more
Manage unplanned breakdowns with defect reporting
SERTICA Defect Reporting provides a simple, structured process for managing unplanned breakdowns. It helps ensure that every unplanned job is documented, tracked, and managed from discovery to resolution.
Availability in practice
Understanding Availability
Availability connects maintenance performance with operations because it shows how much of the required operating period an asset, system, or vessel is ready for use.
It can support decisions related to:
- Vessel utilization: Assessing whether equipment reliability supports the planned operating schedule.
- Charter performance: Reducing the risk of equipment downtime that may contribute to off-hire, subject to the applicable charterparty.
- Operational readiness: Confirming that critical equipment is available when required.
- Drydock planning: Identifying assets that may require major overhaul, inspection, or replacement before the yard stay.
- Critical equipment management: Monitoring systems whose failure could significantly affect safe vessel operations.
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Structure workflows with Dry Dock
Bring your entire docking project into one structured workflow and manage all planning in one platform
How MTBF, MTTR, and availability work together
Looking at only one metric can create a misleading picture:
- High MTBF and low MTTR:
Failures are infrequent, and repairs are completed efficiently, supporting high availability. - Low MTBF and high MTTR:
Failures occur frequently, and restoration takes longer, creating significant downtime and operational risk. - High MTBF and high MTTR:
Failures are uncommon, but each event may have a serious operational impact. - Low MTBF and low MTTR:
Repairs are efficient, but frequent interruptions can still affect operations.
A high availability figure alone does not explain why performance improved or declined. Understanding the result means bringing together data on MTBF, MTTR, planned maintenance, logistical delays, and other downtime causes.
SERTICA does not just help you capture the data. Using the SERTICA Analytics and Dynamic Dashboard module, you can quickly get a visual overview of your KPIs or create the relevant reports you need, for example, reports for upper management or detailed reports for a technical deep dive.
Data quality
Challenges when measuring maintenance performance
These KPIs are only as reliable as the data behind them. Common challenges include:
- Inconsistent failure definitions. MTBF is unreliable when similar events are recorded differently.
- Incomplete maintenance histories. Missing work orders, repair times, or operating hours weaken KPI calculations.
- Manual or delayed data. Late entries increase the risk of errors and gaps.
- Different methods across the fleet. Inconsistent definitions and calculations prevent fair comparisons.
- Comparing unlike assets. Equipment type and operating conditions must be considered before comparing performance.
- Ignoring other downtime causes. Planned maintenance, logistical delays, and operational restrictions may affect availability without being part of active repair time.
- Focusing on isolated results. A single MTBF or MTTR figure provides limited insight without historical trends and supporting maintenance data.
- Reviewing vessels individually. Fleet-wide analysis can reveal recurring equipment issues and differences in maintenance practices that are not visible at vessel level.
When maintenance data is scattered, the full operational cost remains difficult to see. It appears as downtime, reactive work, manual reporting, repeated failures, and repairs delayed by unavailable spare parts.
SERTICA keeps all of that data in one place and is designed to guide users, so the relevant data is captured and logged in a structured, consistent way, which is exactly what reliable KPIs depend on.
Explore examples on how to visualize and monitor maintenance KPIs with dashboards:
Actions
Turning maintenance data into operational improvements
The purpose of MTBF, MTTR, and availability is not simply to produce another monthly report. The metrics should support decisions and continuous improvement.
Technical teams can use them to guide:
- Asset-criticality assessments
- Preventive and corrective maintenance strategies
- Budget and replacement planning
- Spare-parts decisions
- Drydock preparation
- Reliability improvement initiatives
- Fleet-wide performance benchmarking
Getting there depends on consistent data, and that is where a Planned Maintenance System makes a difference. SERTICA Maintenance brings maintenance jobs, component information, histories, documentation, defects, and spare-parts data into a structured environment. See it in action in this short introduction to SERTICA Maintenance:
When crews and shore-based teams record failures and downtime consistently, the system provides a stronger foundation for reliable KPIs and informed maintenance decisions.
Measured and acted on together, MTBF, MTTR, and availability turn maintenance from a monthly report into a way to raise uptime, control costs, and keep vessels operating safely and efficiently.
More about SERTICA Maintenance
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Structure workflows with SERTICA Maintenance
Plan, structure, and execute maintenance jobs in one system to reduce downtime and extend equipment lifetime.
