Routine/ preventive maintenance:

• Regular monitoring of the cooler's performance: temperature difference (delta-T) across the cooler, pressure drop, and flow rates, to detect fouling or leakage.
• Periodic cleaning of the plates (as fouling builds up) and inspection of the gaskets and plates.
• Checking the tightening of the frame bolts (the plate pack is compressed by the frame; over time the bolts may need re-tightening to the maker's torque).
• Checking for leaks at the gaskets and connections.

Dismantling, inspection, cleaning, reassembly:

1. Isolate the cooler (close the sea water and fresh water/ oil valves), drain both sides, and relieve pressure.
2. Remove the end cover and the frame bolts; slide the plates apart carefully (using the correct procedure to avoid damaging the plates).
3. Inspect each plate for corrosion, pitting, cracking, distortion, and damage to the gasket grooves; check the gaskets for deterioration, hardening, cracking or displacement.
4. Clean the plates: remove fouling (scale, sludge, marine growth) using an appropriate method - chemical cleaning (acid/ alkaline solution) or mechanical cleaning (soft brush/ high-pressure water), avoiding damage to the plate surface. Rinse thoroughly.
5. Check the gaskets and renew any that are damaged; ensure the gaskets are correctly seated in the grooves.
6. Reassemble the plates in the correct order (check the plate orientation/ flow pattern), refit the end cover, and tighten the frame bolts evenly to the maker's torque (in a criss-cross sequence).
7. Pressure test the cooler (both sides) to confirm no leaks before returning to service.

• Indications during operation: A rise in the temperature of the cooled medium (e.g. fresh water/ oil) without a corresponding change in load, a change in pressure, or contamination of the cooled medium (e.g. sea water in the fresh water/ oil, detected by salinity/ chloride test or by oil analysis). A drop in the sea water pressure or an increase in the sea water flow may also indicate a leak.
• Confirmation during maintenance: With the cooler isolated and drained, pressure test each side separately (e.g. pressurise the sea water side and check for leakage into the fresh water/ oil side, or vice versa). A leak is confirmed by water appearing on the other side or by a pressure drop. Individual plates can be tested by isolating sections or by dye/ fluorescent leak detection.

• Backflushing: The flow through the cooler is reversed (the sea water/ cooling water is made to flow in the opposite direction through the cooler) for a short period, using the backflushing valves/ arrangement, to dislodge and flush out fouling (marine growth, sludge, debris) that has accumulated on the plate surfaces and in the passages.
• When recommended: When the cooler's performance degrades (increased delta-T or pressure drop) due to fouling, or at regular intervals (e.g. weekly/ monthly) as part of preventive maintenance, especially in sea water service where biofouling is common.
• How it helps: Backflushing removes the fouling layer, restoring the heat-transfer efficiency and reducing the pressure drop, so the cooler operates at its design performance and the need for frequent dismantling/ cleaning is reduced. It is a quick, low-cost maintenance action that maintains efficiency and prevents severe fouling.