Operational Guide · Registers & Logbooks

# Planned Maintenance System (PMS) and Auxiliary Machinery

The silent heart of onboard reliability: how to identify critical equipment under the ISM Code and turn maintenance from reactive into genuinely planned.

ISM Code PMS auxiliary machinery maintenance

## Operational Explanation

The Planned Maintenance System (PMS) translates into daily practice the ISM Code requirement to keep the ship and equipment in conditions consistent with applicable rules and Company instructions. Not all equipment carries the same weight, however: the ISM Code specifically requires identifying equipment and technical systems whose sudden operational failure may result in hazardous situations (critical equipment), reserving stronger reliability measures for it.

The distinction between critical and ordinary equipment is not merely formal: it determines the testing frequency of standby units, the minimum spare parts level to be carried on board, and the priority given during maintenance planning when resources (time, manpower) are limited.

## Regulatory Reference

ISM Code, par. 10 (Maintenance of the Ship and Equipment), in particular par. 10.3: the Company must identify equipment and technical systems whose sudden operational failure may result in hazardous situations, including periodic testing of stand-by arrangements or equipment not in continuous use.

## Scope of Application

Every piece of onboard machinery and technical system, with particular attention to auxiliary machinery (compressors, pumps, cooling systems, generators) whose continuous availability is not always as immediately visible as that of main machinery.

## Procedure / How to Complete It

1. Identify, with the Chief Engineer's involvement, the critical equipment according to ISM par. 10.3 criteria (sudden failure with potential hazardous situation).
2. Schedule differentiated maintenance intervals in the PMS, with reinforced priority for the identified critical equipment.
3. Periodically test stand-by units and equipment not in continuous use, not only the primary equipment.
4. Record every maintenance intervention, including anomalies found and interventions postponed for lack of spare parts or time.
5. Periodically review the critical equipment list, updating it after technical modifications or significant events (failures, near misses).

## Practical Example

Example of identification: an auxiliary cooling pump for the main engine, classified as critical equipment since its sudden failure without a ready standby unit could lead to overheating and engine stoppage underway; tested monthly even when not in primary use.

## Real Cases

Numerous serious failures underway have been traced, in the related investigations, not to an absolute lack of maintenance, but to a PMS that had not correctly classified a component as critical, resulting in maintenance and testing intervals insufficient relative to the real potential impact of its failure.

## Common Mistakes Mistake Library

Mistake | Consequence | How to avoid it
--- | --- | ---
Critical equipment not explicitly identified, treated as ordinary maintenance | Maintenance/testing intervals insufficient relative to the real risk | Systematically apply the ISM par. 10.3 criteria to identify critical equipment
Standby units not tested because 'not in use' | A failure of the primary unit reveals that the standby also fails to work | Periodically test standby units too, not only those in continuous use
Maintenance interventions systematically postponed for lack of time, without tracking the impact on risk | Build-up of backlog maintenance on critical equipment | Explicitly track postponed interventions and their recovery priority

## PSC Observations

The PMS is not typically subject to direct PSC documentary verification as such, but its effectiveness emerges indirectly when an equipment failure (e.g. emergency generator, pumps) generates a deficiency or a detention.

## Operational Tips

- Always involve the Chief Engineer in the periodic review of the critical equipment list, don't leave it as a static document.
- Test standby units periodically with the same discipline applied to those in primary use.
- Explicitly track every postponed maintenance intervention, so as not to lose visibility on the accumulated backlog.

## Checklist

- Critical equipment identified according to ISM par. 10.3
- Standby units tested periodically
- Maintenance interventions recorded, including anomalies and postponements
- Critical equipment list reviewed periodically
- Maintenance priorities reflect real criticality, not just available time

## FAQ

Who decides which equipment is 'critical' under the ISM Code?
The Company, typically with technical input from the Chief Engineer and the shore technical department, applying the ISM par. 10.3 criterion: sudden operational failure of the equipment could generate a hazardous situation.
Do Classification Societies still impose a fixed list of mandatory spare parts?
The role of Classification Societies on spare parts has evolved over the years: the previous Class requirements based on IACS recommendations have largely been replaced by guidelines, leaving the Company greater responsibility for defining minimum stock levels for critical equipment.
Does a well-implemented PMS completely eliminate unforeseen failures?
No: it significantly reduces the probability of predictable failures, but does not eliminate the risk of genuinely unforeseen failures; a well-defined blackout/failure management procedure therefore remains necessary regardless.
🎬 Additional photos, videos and interactive diagrams for this topic will be available in a future version of the platform.

## Related Topics

Critical Spare Parts Management Blackout and Failure Management

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