Continuous Machinery Survey (CMS) Planning & Class Guide
A continuous machinery survey looks like an averaging problem and is not one. The arrangement spreads the machinery special survey across five years, and the usual way of tracking it is to check that about a fifth of the items are being offered each year. That figure can be perfectly healthy while individual items quietly run out of time, because the binding rule is not the yearly percentage — it is that the interval between consecutive examinations of any one item must not exceed five years. The cycle is a convenience; the per-item clock is the obligation.
On schedule overall, out of time on three items
Y1Y2Y3Y4Y5
Track the item clocks, not just the yearly percentage
Why a cycle fails while the percentage looks right
Three things push items toward the end of the cycle, and none of them is neglect. They are ordinary operational pressure, and a superintendent who recognises them early can still move the work.
Items arrive already old
An item surveyed in month one of the previous cycle is four years into its own interval before this cycle starts. Taking over a vessel without reading the last survey dates for each item means inheriting a clock you cannot see.
The easy ones go first
Offering a fifth of the items each year is easiest to satisfy with the items that are quick to open. The heavy jobs are deferred for the right operational reasons and end up in the same year, together.
Attendance is the hidden constraint
Several items need a surveyor present and cannot be delegated. Those have to be arranged around a port call or a yard period, so they bunch where attendance is possible rather than where the clock wants them.
Who may survey what
The division below follows the pattern used by the class societies that publish a confirmatory-survey list. The exact list is society-specific and each case is subject to approval, so it is read as a shape rather than a rulebook — but the shape holds, and it is the thing to plan against.
Machinery
Chief engineer may survey
Surveyor attendance required
Main engine
Cylinder covers and valves, liners, pistons, connecting rods, crankshaft and bearings opened per maker guidance, fuel injection and booster pumps, scavenge equipment, camshaft drive, thrust bearing, turbocharger, governor
Auxiliary diesel engines and auxiliary steam turbines with their coolers and pumps, independently driven pumps, main condensers, air compressors, draught fans, windlass
Reduction and increase gearing, flexible couplings, clutches, holding-down bolts and chocks
Steering
Steering gear pumps
The steering machinery itself
Shafting and propulsion
Intermediate shafts
Propellers, screwshafts, sea connections, gas and steam turbines
Pressure parts
Nothing in this group
Boilers and other pressure vessels, fuel oil heaters other than low pressure, steam and starting air pipes, manoeuvring and bulkhead stop valves
Systems
Refrigeration, liquefied gas and inert gas items within the published list
Inert gas items outside that list, electrical pumping equipment not named in it
The right-hand column is the planning column. Everything in it has to be lined up with a surveyor’s diary, which is why the shafting and sea connection work belongs in a yard period — the practical detail of that scope is covered in our guide to propeller shaft maintenance and alignment.
What a chief engineer survey actually requires
The delegation is real but conditional, and the conditions are where credit is lost. An item opened during routine maintenance at sea only becomes a credited survey if the evidence stands up when a surveyor reads it.
01
Opened for a meaningful examination
Not a partial strip for access to something else. The item has to be opened to the extent that an examination is possible, and the main engine generally also receives a visual inspection by the surveyor.
02
Defects made good with traceable parts
Renewal using parts from the maker or an authorised supplier, with authenticity documents kept. Repairs are verified by a surveyor, and the item is tested under running conditions afterwards.
03
Evidence assembled while the job is open
Findings, parts replaced, authenticity and calibration records, dated photographs, the replaced parts retained on board where practical, and the maintenance and performance logs that sit behind the job.
04
The declaration, signed and distributed
Typically three signed copies — one for the surveyor, one retained on board, one to the company — with the report reaching the surveyor on or before the next periodical survey.
05
The surveyor credits it, not you
A surveyor attends at the next port or on their next boarding to credit the items, and may require a detailed examination or a re-opening if the report does not satisfy them.
One restriction is worth printing out and keeping in front of the chief engineer: delegation is not permitted on machinery known to have sustained damage or to have had a temporary repair. That is exactly the machinery somebody is most tempted to handle quietly, and it is the case where a surveyor has to be involved.
Reading the survey marks
Credit is recorded against each item with a mark, and the marks are not interchangeable. Knowing which one an item carries tells a superintendent how much work the next cycle will need.
X
Opened up with a surveyor present
The full examination. Nothing is outstanding and nothing is conditional on a later review.
E
Credited on the chief engineer’s report
The confirmatory route. The item was opened by ship’s staff and credited on the evidence, with the surveyor retaining the right to ask for more.
G
Substituted by inspection in working order
The surveyor confirms operating condition and reviews the logs instead of an opening. Available where records are in order — and withdrawn where they are not, or where the item has gone a long time without being opened.
The G mark is the one that rewards a well-kept record and punishes a thin one, because the decision to accept it rests on whether the logs support the condition being claimed. That is the same mechanism as the planned maintenance system credit route, applied item by item instead of fleet-wide.
Two timing rules that catch people out
The next due date runs from the examination, not the credit
The following inspection of an item falls due five years from the date the chief engineer examined it, not from the date a surveyor got round to crediting it. A long gap between examination and attendance shortens the next interval rather than extending it, and planning from the credit date quietly loses months.
The report has a deadline of its own
It has to reach the surveyor on or before the next periodical survey. A report written at sea, filed on board and forgotten is not a credited item, and the work has to be done again.
Aligning the cycle with the dry-dock interval
The survey cycle and the docking cycle are separate clocks that have to be made to agree, because one group of items can only be dealt with when the ship is out of the water or shut down alongside. Propellers, screwshafts and sea connections sit in that group, and so in practice do boilers and pressure parts, because the shutdown required is not something a trading vessel offers up casually.
Build the yard survey list a year out
Not at the specification stage. Twelve months before the docking, go through the item record and pull everything whose interval expires before the following docking — those items have one opportunity, and it is this one.
Include the items that only just survive
An item with six months left at the next docking is an item that will expire at sea. Bringing it forward into this yard period costs a little labour now and saves an unscheduled attendance later.
Keep the delegated work out of the yard
Items the chief engineer may open are the most expensive work to buy from a yard and the easiest to do at sea. Every one left on the yard list is labour paid for twice over.
Agree the attendance plan with the surveyor in advance
A yard period with eight attendance items and no plan becomes a sequence of waiting. Agreeing the order and the days means the shaft work and the pressure parts are not competing for the same visit.
The relationship runs the other way as well. A docking brought forward for commercial reasons quietly shortens the window in which several survey items have to be completed, and a docking deferred extends the exposure of every item that was relying on it. Neither is visible from the survey record alone, which is why the two schedules belong on one page rather than in two systems. The interval logic behind the machinery side of that list is covered in our guide to main engine overhaul scheduling, and you can book a demo to see the two cycles tracked against each other.
Recovering a backlog before the cycle closes
If the clocks have already bunched, the recovery is a sequencing exercise rather than a resourcing one. Nothing below reduces the work; it changes where the work lands.
Sort by remaining interval, not by cycle year
Order the list by how long each item has left on its own clock. The items that look latest in the cycle are often not the ones closest to their limit.
Move everything that can be delegated off the yard list
Anything on the confirmatory list is work that does not need a surveyor’s diary. Clearing those at sea frees the yard period for the items that genuinely cannot be done anywhere else.
Ask about working-order credit early
Where records are strong and the item has been opened within reasonable memory, an inspection in working order may be accepted. Asking in advance is useful; asking on the day rarely is.
Treat the schedule as amendable
The arrangement is meant to sit alongside the ship’s own maintenance programme, and the schedule can be revised with class when that programme changes. A schedule nobody has revisited for three years is usually the reason the items bunched.
Persistent non-compliance has a consequence of its own: the arrangement can be withdrawn, and the machinery reverts to being surveyed on the standard pattern with every item that would exceed five years having to be examined inside that limit anyway. The arrangement is a convenience granted on the basis that it is run properly. You can see in a short demo how the item clocks and their evidence are held together.
How Marine Inspection supports a continuous survey cycle
Everything above is a record problem wearing an engineering hat. The limit is per item, the credit depends on evidence assembled while the job was open, and the route available depends on how good the logs are. All three are things a system either holds or loses.
A clock on every item, not on the cycle
Each item carrying its own last-examined date and remaining interval, so the list can be sorted by what is actually closest to its limit rather than by cycle year.
The confirmatory list marked up
Items flagged by whether they can be delegated or need attendance, which is the difference between work you can do on a sea leg and work that has to be booked into a port call.
Evidence captured at the job
Findings, parts and authenticity documents, calibration records and dated photographs attached to the item as the work happens, instead of being reassembled weeks later for a report.
Reports tracked to the surveyor
A chief engineer’s report shown as submitted or still outstanding, so the one that was written and never sent does not cost the credit.
The fleet view a superintendent plans from
Which vessels are bunching, which items are converging on the same yard period, and where attendance has to be arranged — while there is still time to move the work.
Stop planning the cycle and start planning the items
Marine Inspection holds the per-item intervals, the delegation status and the evidence behind each credit, so a survey backlog is visible in year two rather than discovered in year five.
An arrangement that spreads the machinery special survey across a five-year cycle instead of concentrating it, with roughly a fifth of the items offered in rotation each year. The binding requirement is that the interval between consecutive examinations of any individual item does not exceed five years.
Why does a cycle run into trouble when the yearly percentage looks fine?
Because the percentage and the limit measure different things. Items inherited part-way through their own interval, the habit of taking the quick items first, and the need to arrange attendance for certain items all push heavy work toward the same end of the cycle, where several clocks expire together.
Which items can the chief engineer survey?
Typically main engine components including covers, liners, pistons, bearings and the turbocharger, auxiliary engines with their coolers and pumps, independently driven pumps, air compressors, steering gear pumps and intermediate shafts. The exact list is society-specific and subject to approval in each case.
What always needs a surveyor present?
Gearing, couplings and clutches, holding-down bolts and chocks, boilers and pressure vessels, steam and starting air pipes, manoeuvring and bulkhead stop valves, the steering machinery itself, propellers, screwshafts and sea connections, and engine controls and trials.
When is the next survey of an item due?
Five years from the date it was examined, not from the date a surveyor credited it. A long gap between the examination at sea and the attendance that credits it eats into the next interval rather than extending it, and the report itself has to reach the surveyor on or before the next periodical survey.
Can the arrangement be withdrawn?
Yes. Persistent non-compliance can lead to cancellation, after which any item whose interval would otherwise exceed five years still has to be examined within five years of its last inspection. Losing the arrangement removes the flexibility without removing the work.
Survey planning
A backlog found in year five was visible in year two
Marine Inspection keeps the per-item interval, the delegation status and the evidence behind every credit in one place — so the cycle is planned from the clocks that actually bind, and the yard period gets only the work that genuinely belongs there.
