Eight NRF box coolers were delivered to a marine vessel for cleaning, pressure testing and complete overhaul. The pre-service reports indicated that the coolers were severely fouled: heavy fouling from long-term exposure to seawater, multiple spots of hard limestone deposits and incipient leaks. The documentation states, among other things: “very hard limescale,” “already 2 leaking pipes” and visible corrosion on all units.
Because box coolers are essential for cooling the main engine, the repair had to be fast, complete and within the available sailing schedule.
Purpose of the project
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Restoration of full cooling efficiency
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Prevention of engine alarms and unplanned downtime
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Being able to sail reliably without loss of capacity
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Returning all boxcoolers to a 100% functional and coated condition
Challenge/Problem Statement
Symptoms
All eight box coolers were heavily fouled by moss, smallpox, seaweed and corrosion. The fouling formed an insulating layer, preventing the coils from reaching the cold seawater properly.
Normal values:
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Incoming cooling water: ± 80 °C
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Outgoing cooling water: 60 °C
Due to pollution:
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Outgoing cooling water: ± 70 °C
This caused the engine temperature to rise toward 85 °C, the critical point at which the ship can no longer operate at full power.
How did the customer notice this?
The crew noticed in the engine room that both inlet and outlet temperatures were structurally too high. Eventually, the engine threatened to go into alarm.
Risks
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Disruption of the sailing schedule
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Unplanned vessel downtime
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Financial damage: ± €50,000 per day of delay
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Risk of engine damage from prolonged excessive temperature
Complexity
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The work had to be completed within a severely limited time slot
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Two coolers were completely rejected (“Cooler 1 rejected,” “Cooler 2 rejected”)
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Hard lime deposits required multiple chemical cycles
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All units had to be leak proofed
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Tube sheets were to be fully blown and 100% recoated, as advised in the reports
Approach
Blue Orange works according to a structured five-step plan: inspect → clean → test → coat → deliver.
Step 1 – Inspection & Pre-service reporting
The pre-service reports showed:
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No transport crates used (higher risks)
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“Very hard limescale” on inner and outer surfaces
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Multiple spirals with incipient leakage
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Material control: plates/tubes non-magnetic (proper material)
All units were photographed, registered and serially numbered.
Step 2 – Dry cleaning (inside + outside)
All spirals are chemically treated. The reports state:
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“Cleaning inside/outside/very hard limescale”
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“Hard limescale – multiple cycles”
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“Chemical cleaned / pressure tested”
Some parts had to be post-treated manually.
Step 3 – Mechanical finishing & leakage control
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Two units rejected (structural damage)
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Other spirals repaired, cleared of blockages and restored almost to new condition
Step 4 – Pressure testing (5 bar / 30 min)
All usable units have been tested for:
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5 bar
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30 minutes
All approved units passed the test without leakage (Pressure test Approved – Yes).
Step 5 – Blasting & 100% Recoat
As indicated in the official report (“Blasting and Recoat unit 100%“), all tube sheets and spirals were completely recoated.
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Old coating removed
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Fully welded
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New high-quality anti-fouling coating applied
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Finish in line with OEM specifications
Step 6 – Final inspection & documentation
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Coolers visually inspected
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Photos of final result (“Cooler state after cleaning”) show completely clean spirals
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Pressure test forms signed by multiple technicians
Results
Technical result
Heat transfer fully restored
All usable units 100% leak-proof
New coating provides long-term protection against fouling
Cooling temperatures back in operational range
Engine runs at full power again without risk
Operating result
No disruption of the sailing schedule
Hundreds of thousands of dollars in potential damages avoided
Documentation fully traceable and auditable
Installation ready for intensive marine use
Ready for your overhaul project?
Do you want to run your fleet safely and without downtime?
Request an inspection – we’ll make sure your coolers do their job, always.