Survey of diesel main propulsion machinery by a Classification Society

CSM is a class maintenance system in which the items of machinery listed in the Classification Society's rules (main engines, auxiliary engines, reduction gear, shafting, stern tube, thrusters etc.) are surveyed in a continuous rolling programme spread over the class period (usually five years) instead of all at one special survey. Each machinery item is examined at intervals (commonly 12 monthly) in turn, so that over the five-year cycle every listed item is opened up and surveyed. When the survey interval expires the cycle repeats. This spreads the surveyor's attendance, reduces downtime and keeps the machinery under continuing surveillance, with a "continuous" record of survey status in the class register.

Class societies allow approved surveyors, chief engineers and, for many routine openings, the ship's engineering staff to carry out the survey work and to certify it, provided a documented system is maintained and the work is witnessed/inspected by a class surveyor at intervals. This is possible because class societies delegate the actual examination of machinery (e.g. opening of a main engine, inspection of bearings and liners) to the ship's own engineers under a recognised programme, especially where a main engine/oil lubricated system and a well-kept logbook are maintained. The surveyor "attends" only at defined intervals, or trusts the certification of competent staff on arrangements where crew carry out the survey and record it. This reduces attendance and cost while class remains satisfied by audit of records and periodic spot checks.

The ship's planned maintenance system (computerised or paper), which schedules periodic overhauls, service, oil analysis and parts replacement for each machinery item, can be aligned with the CSM cycle. When an item is withdrawn/opened for maintenance under the PMS, the survey of that item required by CSM can be combined with that occasion; the PMS records and reports serve as the documentation and evidence that the survey has been carried out. This avoids extra shutdown, keeps all items surveyed on schedule, provides traceable records for the surveyor, improves breakdown avoidance, and lets the crew time the class surveys to coincide with routine overhauls - saving time and money.

• Main Engine and Large Slow-speed Engine Special Arrangements (e.g. the engine manufacturer's planned maintenance programme approved by Class, combined with oil analysis and cylinder/condition monitoring): Class accepts a scheme where the engine's condition is verified by periodic bore-scope/endoscopic inspection, oil analysis, performance (indicator) data and the manufacturer's recommended overhaul intervals, so physical strip-down at every survey is not required.
• Predictive/Condition-based maintenance and remote/continuous monitoring using approved machinery condition monitoring (vibration, temperature, oil analysis and data trending): Under an approved condition-monitoring programme Class may allow survey credit where the records demonstrate satisfactory condition, reducing the frequency of opening up main/auxiliary engines and shafting.

In both, the records are audited by the surveyor at defined intervals and the class status is maintained without full physical opening on every occasion.