Approved Planned Maintenance Systems: Meeting Class Requirements (DNV, BV, LR, ABS)

Opening a perfectly healthy auxiliary engine simply because the class calendar says so: every chief engineer knows the feeling. At the other extreme, watching a surveyor refuse to credit a machinery item because the records do not prove what was done means a longer drydocking, a Condition of Class and a bill nobody budgeted for. Between the two sits a framework recognised by every major classification society: the approved planned maintenance system, usually called an approved PMS or Machinery PMS.

The principle is easy to state and demanding to sustain. Class accepts that maintenance carried out by the ship's staff, at intervals and against acceptance criteria derived from the manufacturer's recommendations, counts as survey of the machinery items concerned. The chief engineer plans and executes; the surveyor verifies annually that the scheme works. Verification shifts from physical sampling to documentary proof — and that is where many owners and managers come unstuck.

Class survey cycle, approval conditions at DNV, Bureau Veritas, Lloyd's Register, RINA and ABS, approved condition based maintenance, and what the annual audit really covers: here is what to know before applying. With one conviction from the field: without structured maintenance management software, an approved PMS does not survive three years.

1. The class survey cycle: the calendar nobody negotiates

Classification rests on a five-year cycle punctuated by mandatory milestones. Keeping class — and with it hull and machinery insurance validity, flag State compliance and charterer acceptance — depends on meeting that calendar. Windows vary slightly by society and ship type, but the framework is harmonised across IACS members and dovetails with the IMO Harmonised System of Survey and Certification.

Note the last line. An approved PMS replaces neither the bottom survey, nor the hull renewal survey, nor any statutory certification. It applies to machinery items under continuous survey. Confusing the two is the most common misunderstanding in discussions with class.

Continuous survey of machinery is the entry ticket

Three machinery survey regimes coexist: the normal system, where all items are surveyed at the five-yearly renewal; the continuous system, where items are spread over five years and part of the examination may be carried out by the chief engineer before a confirmatory survey; and the planned maintenance survey system, where each item has its own maintenance scheme. Bureau Veritas sets out this progression explicitly. Moving to PMS therefore assumes, almost always, that the ship is already on continuous survey of machinery.

2. What class actually expects from maintenance

Class does not ask for "maintenance". It asks for demonstration that adequate maintenance was carried out, at the right time, by competent people, with the right parts, and that the condition found was recorded. At an audit, what is not recorded did not happen.

The foundation is the ISM Code, whose element 10 requires the Company to establish maintenance procedures, hold inspections at appropriate intervals, report non-conformities, take corrective action, keep records, and identify equipment whose sudden operational failure may result in hazardous situations. An approved PMS builds on that foundation without replacing it — see our article on the ISM Code and maintenance software.

In substance, an acceptable plan is built on the maker's recommendations: scope of work, interval, and quantified acceptance criteria. A job card saying "annual turbocharger overhaul" and nothing else will not pass: you need the procedure, the limit, and the record of the measured value. That is the logic of a methodically built preventive maintenance plan.

3. What an approved PMS changes in practice

Survey credit moves on board

Planned maintenance carried out and recorded on board, under the chief engineer's responsibility, earns survey credit for the items concerned. Lloyd's Register makes the mechanism explicit: the chief engineer may examine applicable machinery items without a surveyor present and issue an Interim (I) credit; the surveyor then issues a Confirmatory (C) credit on the basis of the records, or an Examination (X) credit where an item is opened out in his presence. Every applicable item must be credited once in each five-year period, and LR is clear that it is for the chief engineer to distribute those credits across the cycle.

Planning returns to the ship

Without an approved PMS, the date of an overhaul is largely set by surveyor availability. With one, it is set by running hours, actual condition and trading pattern: you open an engine during a technical call you have chosen, not because a signature is needed before a deadline. RINA sums up the benefit in a line — survey is based on equipment running hours instead of fixed calendar time. For a ferry in high season or a tug on contract, that freedom is worth a great deal.

Benefits and limits

• No systematic opening out of all items at the five-yearly renewal: DNV presents its PMS as an alternative to the traditional five-yearly inspection approach.
• Intervals aligned with OEM recommendations, and therefore with real component life.
• Off-hire under better control: overhauls spread across the cycle rather than concentrated in the drydocking window.
• An evidence file reusable for vetting, sale and purchase due diligence and insurance claims.

It is not a blank cheque. Rules reserve for the surveyor the parallel operation trials of generators, testing of protection and safety devices, load trials, automation surveys and pressure vessels. Several rule sets prevent the chief engineer from crediting the same item twice in succession. And the surveyor retains the right to require an item to be opened up if not satisfied with its apparent condition.

4. Eligibility and the application file

Prerequisites

• Ship on continuous survey of machinery, up to date with surveys, with no Condition of Class outstanding on the items concerned.
• A system already running for several months: approval procedures commonly expect around six months of operation, so the database holds genuine history rather than nothing.
• Software accepted by the society, either through product type approval or case-by-case acceptance. DNV, Bureau Veritas and others issue such certificates to PMS vendors.
• The chief engineer formally designated as the person responsible on board, with named user access rights.
• A system usable in English and a trained crew, able to demonstrate competence to the surveyor.

Documentation to submit

1. Organisation chart of responsibilities ashore and on board: Designated Person Ashore, superintendent, chief engineer.
2. Procedures for filing and retaining documents and records.
3. The list of equipment proposed for the scheme, aligned with the list of items under continuous survey.
4. The procedure for identifying and physically tagging machinery, matching the tag to the software code.
5. A preventive maintenance sheet for each machine: tasks, interval, acceptance criteria, maker's reference.
6. The forward maintenance schedule across the five-year cycle.
7. Trend monitoring, data backup and access control procedures.
8. The annual report on the operation of the scheme, submitted to the society.

The implementation survey

Document approval is not enough. An implementation survey takes place on board, usually within a year. The surveyor tests the system against the real ship: is the machinery list complete? Do tags match the software codes? Are the records consistent? Can the crew operate the tool? Three outcomes are possible: satisfactory, satisfactory with remarks to clear, or unsatisfactory — in which case a new survey is required after rectification, with the attendance fee applying either way. The Equipment module is what makes the difference at this stage: without a clean asset tree and reliable running-hour readings, the survey ends in remarks.

5. Approved condition monitoring and CBM

An approved PMS fixes intervals; condition based maintenance replaces them with a measurement of actual condition. Class accepts it provided the monitoring arrangement gives a degree of confidence in the condition of the machinery equivalent to or greater than traditional survey techniques.

Recognised techniques

• Lubricating oil analysis: spectroscopy, ferrography, viscosity, particle counting, water content. The most mature tool for engines, gearboxes and shafting — and a condition of extended tailshaft survey intervals.
• Vibration analysis: imbalance, misalignment, bearing deterioration and excessive clearances on pumps, fans, alternators and reduction gears.
• Infrared thermography: loose electrical connections, bearing overheating, fouled heat exchangers, failing insulation.
• Performance monitoring: pressures, temperatures, flows, consumption, combustion diagrams — the richest and least exploited data source on board.
• Non-destructive testing: ultrasonics, dye penetrant, magnetic particle, eddy current.

What class requires around the measurement

The point is not the technique but the framework around it. Rules require limiting parameters based on OEM guidelines or a recognised international standard, not on in-house judgement. They require the original baseline data together with all condition monitoring data accumulated since the machine was last opened, a procedure governing changes to software and monitored parameters, and evidence of personnel qualifications. ABS guidance on equipment condition monitoring grades those skill levels explicitly: thermography and vibration analysis belong to trained and experienced technicians.

A single reading proves nothing. What class assesses is a trend — a dated, traceable series compared against a baseline and a threshold. Our article on moving from corrective to condition based maintenance sets out the steps. The society keeps the right to require an opening up or an independent test whatever the monitoring shows.

6. The annual audit: what the surveyor really checks

The audit is harmonised with the class Annual Survey. Its purpose: to confirm the scheme is being correctly operated and that the machinery has functioned satisfactorily since the previous audit. What actually gets examined:

• The annual report on the scheme: work carried out, breakdowns, repairs, changes to the equipment list.
• Planned, completed, overdue and postponed tasks: the volume of overdue work is the first indicator looked at.
• Traceability of each job: who, when, at what counter reading, which measurements, what verdict against the acceptance criterion, which parts fitted.
• Justification of postponements: postponing is not a fault; postponing without justification and approval is. Reason, approving authority and new due date must be in the system.
• Corrective maintenance: damage must have been reported to class, repaired and recorded, and the repair is verified at the audit. Several rule sets ask that replaced parts be retained on board.
• Spare parts: availability of critical spares, consistency between stock issues and jobs declared, traceability of part numbers and material certificates.
• Personnel qualification: certificates of competency, training on the system, credentials for condition monitoring.
• Consistency between software and machinery: the surveyor goes into the engine room and compares what is there with what the records claim. Upkeep incompatible with a spotless history triggers immediate deeper examination.
• Document control: access rights, current backups, non-editability of closed records.

Key takeaway — The annual PMS audit is not an audit of maintenance; it is an audit of the evidence of maintenance. The surveyor is not only asking whether you look after the ship, but whether you can demonstrate it item by item, date by date, reading by reading. An excellent engine team with loose records will lose the credit; a disciplined, properly equipped team will keep it.

7. Common grounds for suspending the credit

The rules converge: the survey arrangement under PMS or CM/CBM may be cancelled if the scheme is not satisfactorily carried out. The recurring causes:

• Exceeding agreed intervals: the number one cause. Overhauls pushed beyond approved intervals without justification or approval are enough on their own.
• Incomplete or inconsistent records: jobs closed with no measurement, no part, no signature — or keyed in en masse the day before the audit. Timestamps tell the story.
• Unreported damage: a major repair found during the audit and never reported to class is a breach of trust.
• Divergence between system and reality: condition contradicting the history, missing tags, equipment replaced without updating the list.
• An outstanding Condition of Class on an item inside the scheme: the item is normally removed until cleared.
• Critical spares missing, or stock records that do not match physical inventory.
• Change of manager, owner or classification society: the approval lapses and must be reconsidered.
• Data loss: no usable backup after an IT failure.

8. Asset hierarchy and coding: the condition of an auditable PMS

A PMS is auditable only if you can trace a physical item of equipment to its full history in under a minute. That is decided when the asset tree is designed, not the night before the audit.

Structure

Use a stable four- or five-level hierarchy: vessel → functional system → sub-system → equipment → replaceable component. For example: Vessel → Propulsion → Main engine → Turbocharger → Cartridge. The golden rule: the level at which a job is recorded must be the level at which you will later need to produce evidence. Recording everything against "main engine" makes the history useless. Every item on the class list must map to an identifiable node in the tree.

Coding

• A unique, immutable code per item, never reused even after the machine is replaced.
• A readable code: function + location + sequence number, for example ME-TC-01 for main engine turbocharger no. 1.
• A physical match: plate, engraved label or QR code on the machine. Approval procedures require it, and it is the first thing a surveyor checks.
• Consistency with drawings and the engine room log.
• Spare parts coding linked to equipment, in both directions.

Connect counters, stock and purchasing

Three flows must converge on the same equipment record. Counters trigger jobs on actual running hours. Stock records the part consumed on the job — the link surveyors ask for most often and the one most often missing, as we explain in our guide to MRO inventory management. Purchasing closes the loop by documenting the origin and conformity of the part fitted.

9. The maintenance system as the evidence base

From class's point of view, an approved PMS is a documentary system before it is a planning tool. Rules expect a computerised system with controlled access rights, regular backups and usable records. Marine maintenance software is therefore not a convenience but the evidence infrastructure of the arrangement. What it has to deliver:

• Timestamp and signature on every job closure, not editable afterwards.
• Offline data entry: at sea, a system that needs connectivity produces delayed entries and therefore suspect histories. The Smart Sailors mobile app works offline and synchronises when the link returns.
• Structured export of history by equipment and period, usable by the surveyor or transferable to class machinery-data platforms — DNV, for instance, has industrialised remote review of PMS data across entire fleets.
• An overdue and postponed work dashboard with reason and approval: the Dashboard must answer the audit's first question on one screen.
• Survey and certificate due-date tracking, to align PMS jobs with the class calendar through the Certificates module.
• Crew competence records and workload forecasting across the five-year cycle, so overhauls are spread rather than piled into the final year.

With more than 400 vessels equipped, we see one constant: the operators who keep their survey credit without drama are those who did the asset-tree and coding work before applying for approval, and who record work as it happens rather than in catch-up mode.

FAQ

Does an approved PMS remove the five-yearly renewal survey?

No. It removes the requirement to open out the machinery items covered by the scheme, planned maintenance counting as survey for those items. The hull renewal survey, the bottom survey, thickness measurements, the trials reserved for the surveyor and all statutory surveys remain due.

How long does it take to obtain an approved PMS?

Allow time to assemble the file — asset tree, job cards, maker's intervals, procedures — then a period of genuine operation, since approval procedures commonly expect around six months of history before the implementation survey. On a ship whose technical documentation is in order, six to twelve months from decision to certificate is a realistic order of magnitude observed in the field.

Does the software have to be approved by the classification society?

Societies issue type approval certificates to PMS products and also accept case-by-case approval of the system used on board. Either route examines the same requirements: access control, backup, record integrity, export capability and availability in English.

What happens if a job is overdue at the audit?

An isolated overdue item, documented, justified and given an approved new due date, does not normally attract a sanction. What triggers a remark and then suspension is unjustified overdue work, systemic lateness across a family of equipment, or exceeding approved intervals on critical items.

Can condition based maintenance fully replace calendar-based PMS?

Not fully, and not immediately. Approved CBM applies to items for which you can demonstrate reliable monitoring: limiting parameters from the OEM or a recognised standard, baseline data, trend history, qualified personnel. In practice operators combine both regimes, and the society keeps the right to require an opening up.

Is an approved PMS relevant to smaller vessels and yachts?

Yes, provided the vessel is classed and on continuous survey of machinery. Large yachts, mid-size passenger ships, tugs and workboats use it routinely, and it is on units with small crews that automating data capture pays back fastest.

Conclusion

Obtaining an approved PMS is a project of a few months; keeping it is a daily discipline. The difference comes down to three things: an asset tree aligned with the list of items under survey, job cards with quantified acceptance criteria from the maker, and data entry done at the time of the job rather than three weeks before the audit. Once earned, that credit changes how a fleet is run: maintenance becomes an operational choice rather than a calendar constraint.

Preparing an approval application, or want to de-risk your next annual audit? Book a demonstration of Smart Sailors, or trial the platform free for 30 days to see, on your own machinery hierarchy, exactly what the surveyor will see. Our pricing starts at 10 EUR per vessel per month.