Ship machinery condition monitoring: what to watch on board
Which shipboard machines to monitor, the faults that matter on each, and how to run condition monitoring at sea when the link to shore comes and goes.
Why ships are different
Condition monitoring on a ship follows the same physics as in a plant: rotating machines tell you how they are wearing through vibration, current, temperature and their operating data. What changes is everything around the measurement.
- Nobody is coming. At sea the engine crew is the only maintenance team. A fault has to be found early enough for them to plan the repair around watches, spares on board and the next port call.
- The link to shore is unreliable. Satellite bandwidth is limited and often shared with crew and operations. A system that sends raw data to a cloud before it can say anything doesn't work mid-ocean.
- Steel blocks radio. Bulkheads and decks split the engine room into spaces that ordinary wireless networks don't cross reliably.
- The hull itself vibrates. Propeller blade pass, main engine firing and sea state all reach every machine through the structure, so a reading has to be judged against the ship's own background, not only against a land-based limit.
- Load and speed change all the time. Generators follow the electrical load, pumps follow the plant, and the main engine follows the voyage. Trends need to compare like with like.
What to monitor, and the faults that matter
| Machine | Faults to look for | Main measurements |
|---|---|---|
| Diesel generator sets | Misalignment and coupling wear, bearing wear, looseness of the mounts, electrical faults in the alternator | Vibration on the engine, coupling and alternator bearings; current and voltage |
| Fuel and lube oil separators | Bowl unbalance from uneven sludge, spindle bearing wear, drive gear wear, poor separation | Vibration at the bowl speed and gear mesh; operating data such as start-up time and discharges |
| Cooling water and ballast pumps | Cavitation, impeller unbalance, misalignment, bearing defects | Vibration, suction and discharge pressure, motor current |
| Air compressors | Valve faults, bearing wear, looseness | Vibration, discharge temperature, run hours |
| Main engine auxiliaries and turbochargers | Unbalance, bearing wear, rubbing | Vibration, speed, temperatures |
| Shaft line, gearboxes, thrusters | Misalignment, gear wear, bearing defects | Vibration, gear mesh frequency and sidebands, temperatures |
| Steering gear | Resonance, pump wear, looseness | Vibration, hydraulic pressure |
| Deck and port cranes | Bearing and gear wear under cyclic loads | Vibration during lifts, motor current |
A useful order for a first installation is by consequence: the machines whose loss stops the ship or its cargo work first, then the ones with no redundancy, then the rest. On most vessels that puts generator sets, separators and the main cooling pumps at the top of the list.
Making it work offline
The answer to an unreliable link is to do the analysis on board. Sensors report to a local network inside the ship, an edge computer in the engine room runs the diagnosis, and the engineer sees the result on the ship's own screen. When a connection is available, findings and summaries go ashore to the technical superintendent; when it isn't, nothing on board waits for it.
Three things to check in any shipboard system:
- Diagnosis on board, not only data collection. Storing readings until the next port means finding faults after the voyage they could have saved.
- A network built for the hull, with repeaters or wired links between spaces, so a closed watertight door doesn't cut off half the sensors.
- Small uploads. Sending findings and trends, not raw waveforms, keeps satellite use low and lets the shore team follow the fleet.
Classification societies and planned maintenance
Major classification societies, such as DNV, ABS and Lloyd's Register, accept condition-based maintenance arrangements in which monitoring data can stand in for some scheduled open-up inspections of machinery. The detail differs between societies, so check your class rules before relying on monitoring data for survey credit. Either way, a well-kept condition record makes the planned maintenance system more accurate and shows a surveyor how a machine has been running.
An example from a pilot
On a bulk carrier nine days from the next port, with no usable link to shore, Prism running on the vessel's edge computer flagged angular misalignment on a generator two days into the crossing and tied it to a coupling element replaced in port. The crew shimmed and re-torqued the set at the next change-over, about four hours of work, and the following run confirmed the fix. The ship never needed the port to find or fix the fault. The signature Prism used is described in misalignment vibration spectrum.
How Misoki uses this
Misoki for marine and ports runs Prism AI on board: its own local network links the sensors, the analysis and findings stay on the ship's computer with no connection needed, and summaries go ashore when a link is available. For separators, see fuel oil separator condition monitoring.
Frequently asked questions
01Which ship machinery benefits most from condition monitoring?
Start with the machines whose failure stops the ship or its cargo work and that have no redundancy: diesel generator sets, fuel and lube oil separators, main cooling water pumps, then compressors, steering gear, shaft line gearboxes and cranes.
02Can condition monitoring work on a ship without internet?
Yes, if the diagnosis runs on board. Sensors report to a local network in the ship, an edge computer analyses the data, and the engineer sees findings locally. Results go ashore only when a connection is available.
03Does condition monitoring count towards class surveys?
Major classification societies offer condition-based maintenance arrangements where monitoring data can replace some scheduled open-up inspections. Requirements differ between societies, so check the rules of your class before relying on it.
Find faults at sea, not in port.
Tell us about your vessel and we walk you through what Prism would watch on board.