What is a planned maintenance system on a ship? ISM Code, class and practice

What is a planned maintenance system on a ship?

A planned maintenance system is a structured way of deciding what maintenance each item of equipment needs, scheduling it, and recording what was actually done. On a modern merchant ship it is almost always software, with one database on board and a copy in the office.

A working PMS has four parts:

• An equipment register: every maintainable item, from system down to component, with maker, model and serial number.
• A job library: the inspection, testing and maintenance tasks for each item, with intervals and clear instructions.
• Records: completed jobs, measurements, defects and repairs, signed by the responsible person.
• Spares and stores: parts linked to the equipment they fit, with minimum stock levels.

IACS Recommendation 74, its guide to managing maintenance under the ISM Code, says a systematic approach "will begin with the establishment of a comprehensive asset register". Everything else in the system depends on that register being complete.

Does the ISM Code require a planned maintenance system?

The ISM Code does not use the words "planned maintenance system", but section 10, "Maintenance of the ship and equipment", sets out what one has to deliver. The company must:

1. Establish procedures to keep the ship maintained in line with the relevant rules and regulations and any additional company requirements (10.1).
2. Inspect at appropriate intervals, report any non-conformity with its possible cause, take corrective action and keep records (10.2).
3. Identify critical equipment: equipment and technical systems "the sudden operational failure of which may result in hazardous situations", with specific measures to promote their reliability, including regular testing of stand-by arrangements and equipment not in continuous use (10.3).
4. Integrate those inspections and measures into the ship's operational maintenance routine (10.4).

A PMS is the usual way to show all four to an auditor. IACS Recommendation 74 also links maintenance to other parts of the Code: the designated person (section 4), resources and personnel (section 6), non-conformities and accidents (section 9), document control (section 11) and the company's review of the SMS (section 12). It notes that more port state control detentions attributed to safety management failures have referred to maintenance than to any other clause of the ISM Code. See our ISM Code and SMS guide for the rest of the Code.

What is critical equipment under ISM Code 10.3?

Critical equipment is whatever the company identifies as equipment or systems whose sudden failure could cause a hazardous situation. The Code does not give a list; the company must make one for each ship type and trade.

IACS Recommendation 74 gives examples of stand-by and infrequently used equipment that should be inspected and tested under the maintenance plan:

In the PMS, critical equipment should be flagged so the office can see its status separately, with tests scheduled at defined intervals and overdue jobs escalated. An emergency generator and a galley fan should never look the same on a maintenance report.

How does a class-approved PMS replace continuous machinery survey?

Classification societies normally survey machinery under a Continuous Machinery Survey (CMS) scheme. Items are offered for survey in rotation so that the interval between examinations of each item does not exceed five years; Indian Register's guidelines say about one fifth of the items are examined each year.

IACS Unified Requirement Z20 allows an approved Planned Maintenance Scheme for machinery as an alternative to CMS. Survey is then based on the overhaul intervals in the PMS, using maker's recommendations, documented operator experience and condition monitoring where fitted. The main points of UR Z20 (Rev.1, July 2018) are:

The last row matters to ship managers taking over a ship: a class-approved PMS does not transfer automatically with the vessel. IACS UR Z27 adds requirements for condition monitoring and condition-based maintenance schemes, which apply only to ships already on an approved PMS survey scheme.

Each class society applies these requirements through its own rules, so check your class society's procedure before applying.

What types of maintenance jobs go into a PMS?

A good job library mixes three kinds of trigger, chosen for each item:

• Calendar jobs: fixed intervals such as weekly, monthly or annual. Used for safety equipment, stand-by machinery and anything that deteriorates with time rather than use.
• Running-hour jobs: triggered by counters, for main and auxiliary engines, purifiers, compressors and pumps. They only work if counters are updated reliably.
• Condition-based jobs: triggered by measurements such as vibration, lube oil analysis or temperature trends, where an approved condition monitoring scheme is in place.

IACS Recommendation 74 says intervals should be set from the maker's recommendations, condition monitoring where used, operating experience and failure history, how the equipment is used (continuous, intermittent, stand-by or emergency), what can only be done in dry dock, and class, convention, flag and company requirements. Record the reason whenever an interval departs from the maker's manual.

Some regulations now set their own expectations. Since 1 January 2026, SOLAS II-1/3-13 has required lifting appliances and loose gear to be inspected, tested and maintained to IMO guidelines, and those records may be kept in the PMS if they meet the conditions. We cover this in SOLAS II-1/3-13 lifting appliances: what your PMS needs.

How should defects and spares link to the PMS?

Defects and spares are where a PMS proves it reflects the real ship.

Defects. ISM 10.2 requires non-conformities to be reported with their cause and corrected. IACS Recommendation 74 adds that the company should address the maintenance system failure behind a defect, check whether the lesson applies to other ships, and verify that the corrective action worked. In practice, every defect should be raised against the equipment item in the PMS, not in a separate log, so the item's history is complete. Vetting inspectors check this too: SIRE 2.0 question 2.4.1 compares the defects the crew know about with what the defect system shows (see our SIRE 2.0 guide).

Spares. Each job should list the parts it needs, and critical equipment should have minimum stock levels. When parts are not linked, engineers guess requisitions and the office cannot see whether a ship can actually carry out an overdue job.

What records does a planned maintenance system need to keep?

IACS Recommendation 74 divides maintenance records into two groups:

The same records serve as management information. Trend analysis of defects and repeat failures can justify changing an interval, or show a problem that needs a longer-term fix.

What are the benefits of a planned maintenance system?

The benefits of a planned maintenance system come from replacing memory and paper with one shared record:

• Compliance evidence: ISM 10, class surveys, PSC and vetting inspections all ask for the same maintenance history.
• Fewer failures: critical and stand-by equipment is tested before it is needed.
• Survey efficiency: an approved PMS can be credited for class machinery survey.
• Handover continuity: a relieving Chief Engineer sees what is due, overdue and deferred.
• Office oversight: superintendents see the fleet's maintenance status without waiting for reports.
• Better spending: spares and repairs are planned rather than urgent.

None of these benefits survives poor data. A PMS that shows every job in date while the equipment is not maintained as the maker intended is worse than no system, because it hides the risk.

How do you build or clean up a PMS database?

The database decides whether the PMS works. Most failures trace back to the first data load: missing equipment, intervals copied without review, no starting status, and parts not linked. A sound approach:

1. Walk the ship and build the equipment list from what is installed, checked against drawings and class records.
2. Standardise names and coding across the fleet so the office can compare ships.
3. Review job intervals with the Chief Engineer and record any departure from the maker's manual.
4. Set the starting status from evidence: last overhaul reports, running-hour counters and class records.
5. Flag critical equipment in line with the SMS.
6. Link spares and certificates before go-live.

Our team builds and cleans PMS databases as a service; see PMS database creation. For how to get the first data load right, see our article PMS database creation: get the first data load right.

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