A cargo pump rarely fails without warning. The warning shows up as a purge result, an oil sample, a repeat alarm or a discharge that takes longer than it did last voyage. The job of the Chief Engineer, the Chief Officer and the rest of the team is to read those signs in time. This guide covers mechanical seals, bearings, performance testing and the records that show a tanker's cargo pumps are being looked after.
How a Submerged Cargo Pump Is Built and Where Each Part Can Fail
Why the cofferdam sits between the hydraulic section and the cargo, and what that gives you
Submerged cargo pumps of the Framo type sit inside the tank and are driven hydraulically from deck. Framo describes the cofferdam as a protective space that separates the hydraulic section from the cargo and supports seal monitoring. Leakage past the cargo seals or the hydraulic oil seals collects there and is routed to a deck exhaust trap where it can be measured. Framo calls this a simple and reliable seal condition monitoring system that needs no electric sensors.
What to check at each level of the pump, from deck connections to the suction well
The drawing below follows the pump from the deck down. Each row shows what the part does, what to check and the type of checkpoint. The checks come from Framo's public pages and a secondary maintenance summary. Where the source is secondary we say so, because intervals and procedures must be confirmed in your pump maker's manual.
Mechanical Seals and Cofferdam Purging: Reading the Early Warning
How often to purge the cofferdam, and what Framo says the exhaust can tell you
Framo says the cofferdam is purged before and after each loading and discharge operation. It also gives a fortnightly purge at sea. Compressed air or nitrogen is pushed into the cofferdam and released through the exhaust pipe on deck. Water vapour or oil in the exhaust suggests seal leakage. Framo also offers analysis of submitted purge data and crew training.
| What comes out of the exhaust | What it may mean | Suggested next step |
|---|---|---|
| Clean air only | Seals appear tight at the moment of the test | Record the result and the date, and continue the routine |
| Water vapour or water | Water has reached the cofferdam. Framo says water vapour or oil suggests seal leakage. | Record it, repeat the purge and compare with earlier results |
| Hydraulic oil | Oil has passed a seal. Framo says oil suggests seal leakage. | Record it, check the hydraulic oil level and plan seal work |
| Cargo vapour or liquid | Cargo may be passing the cargo seal (our reading) | Treat as a defect, follow your cargo and gas safety procedures and plan repair |
| No flow, a blocked exhaust | Seal condition cannot be checked. A secondary summary says such a pump should not be used. | Clear the cofferdam or take the pump out of service per the manual |
Why seal sets are replaced in pairs, and why the purge log should drive the seal plan
A secondary summary of Framo maintenance practice says seal sets have an upper and a lower seal and that both must be replaced together, with spare seals kept on board. It also says the purge result indicates seal condition and helps plan seal changes. A purge log that is read, not just filled in, lets you plan seal work for a port stay, instead of finding out during discharge.
Bearings, Wear Alarms and Debris: Catching Mechanical Damage Early
What a repeat wear indication alarm on one pump tells you, and the four steps to respond
A secondary summary of Framo practice gives no fixed bearing interval. Instead it ties bearing checks to alarm behaviour: if the wear indication alarm repeats for the same pump while the other pumps show no alarm, check and replace the bearings. The response below is from that summary. Check it against your manual.
Why a bearing failure inside the tank is a fire risk and not only a pump repair
A US Coast Guard safety alert describes a chemical tanker where preliminary findings were that an upper cargo pump bearing failed, the shaft and impeller moved about half an inch and the impeller spun against the casing end plate. Friction heat and possible sparks probably ignited the tank atmosphere, and opening the tank top cover admitted air. The pumpman was badly burned. The cause chain is simple, and every link is a maintenance issue.
Performance Testing: Wear Rings, Discharge Time and Stripping
How worn wear rings show up in stripping, parallel pumping and discharge time
A secondary summary says wear ring wear depends on cargo type and running hours, with symptoms including poor stripping performance and problems with parallel pumping. It says worn rings increase discharge time, and that rings are normally changed whenever the pump is overhauled for other reasons. A closed-valve test with calibrated manometers is normally done by a service engineer, at pre-docking or special attendance.
Why a simple baseline of discharge time and stripping notes beats testing only at dry dock
Between service visits, the ship's own records are the only performance data. Log the time to discharge each cargo quantity, the pump's pressure and the stripping result. Over several voyages, a drift upward shows up long before a formal test. This is our suggestion. Thresholds should come from your pump maker and your own history.
Hydraulic Oil, Filters and Coolers: The Drive Side of the Pump
Which oil, filter and cooler checks keep the hydraulic drive clean and cool
A secondary summary of the Framo manual lists particle counting and water analysis every three months and a full oil analysis once a year. It says to replace the filter element after a high differential pressure indication or contamination above 16/12 according to ISO 4406, to avoid mixing hydraulic oils and to vent after any hydraulic service. For coolers it gives anode inspection every three months for sea water coolers and annually for fresh water coolers, and tube cleaning every six months or annually. Confirm these against your own manual.
| Task | Interval | Source and status |
|---|---|---|
| Purge cofferdam | Before and after each loading and discharge | Framo (maker's public page) |
| Purge cofferdam at sea | Every two weeks | Framo (maker's public page) |
| Hydraulic oil particle count and water analysis | Every 3 months | Secondary summary of the Framo manual |
| Full hydraulic oil analysis | Once a year | Secondary summary of the Framo manual |
| Debris detectors, if fitted | Every 3 months | Secondary summary of the Framo manual |
| Oil cooler anodes | Every 3 months for sea water coolers, annually for fresh water coolers | Secondary summary of the Framo manual |
| Oil cooler tube cleaning | Every 6 months for sea water, annually for fresh water, or sooner if heat exchange is too low | Secondary summary of the Framo manual |
| Operate service valves | Annually | Secondary summary of the Framo manual |
The Records and Checklist That Show the Pumps Are Looked After
A cargo pump checklist with a checkpoint type on every item
Inspectors observe normal work and interview crew on their duties, according to OCIMF, so what the crew do and what the records show should match. We could not access the SIRE 2.0 question library chapters on cargo and ballast systems, so we do not list questions here. Read your chapters for the exact wording. For how the questions are grouped, see our SIRE 2.0 CVIQ question types: core, rotational, campaign and conditional.
| When | Check | Checkpoint type |
|---|---|---|
| Before loading or discharge | Purge the cofferdam and read the exhaust | Test |
| Before loading or discharge | Check hydraulic oil level and filter differential pressure | Measure |
| During discharge | Watch alarms, pressures, temperatures and abnormal noise | Visual |
| During discharge | Log the time to discharge the cargo quantity | Record |
| After discharge | Purge the cofferdam again and compare with the pre-discharge result | Test |
| After discharge | Record stripping performance and any remaining cargo | Record |
| At sea, every two weeks | Purge the cofferdams of idle pumps | Test |
| Every 3 months | Take hydraulic oil samples and review particle and water results | Measure |
| Before dry dock | Arrange wear-ring and performance testing by the service engineer | Test |
| Always | Keep spare seals and critical spares aboard | Record |
How to keep purge logs, oil results and defects together so the story is easy to tell
A pump with a clean purge history, regular oil results, a short defect list and a clear spare parts record tells a surveyor the ship is looked after. For the whole inspection, see our SIRE 2.0 inspection guide to the OCIMF tanker vetting programme.
Mistakes That Turn a Small Pump Problem Into an Off-Hire Pump
Six habits that let seals, bearings and oil problems grow unnoticed
Systems That Keep Pump Logs, Oil Results and Defects in One Place
How a dated photo repository, task ownership and deadlines make pump maintenance visible
Cargo pump upkeep is a long series of small, dated checks. Marine Inspection supports a dated photo repository, observations turned into tasks with owners, deadlines and evidence, and certificate and equipment tracking. That lets the Chief Engineer and the superintendent see each pump's history and open items in one place.
