Plate Heat Exchanger

Frame, carrying bar and tightening bolts

The frame clamps the plate pack to a specified compressed thickness; under-tightening lets gaskets leak, over-tightening deforms plates and shortens gasket life.

Brazed or welded pack (compact type)

Copper-brazed or fully welded plate packs eliminate gaskets entirely, giving a smaller, higher-pressure-rated unit that cannot be opened for mechanical cleaning, only backflushed or chemically cleaned.

Selection and sizing

• Duty and approach temperature - the closer the required approach temperature between the two fluids, the more plates or the larger the area needed.
• Pressure rating - gasketed units typically handle up to around 25 bar; brazed and welded types reach substantially higher.
• Fouling tendency of the fluid - seawater cooling duty favours a gasketed, openable design for periodic mechanical cleaning; clean closed-loop duty suits brazed units.
• Materials - titanium plates for raw seawater service resist chloride pitting far better than stainless steel.
• Connection size and plate count - determines physical footprint against available engine room space.

Regulations and class

Plate heat exchangers used in essential services (main engine cooling, fuel heating for combustion) fall under the class society's pressure vessel and piping rules for design pressure, material certification and pressure testing before delivery. Where the exchanger separates a fuel or lube system from a cooling water system, class rules typically require the design to prevent internal cross-contamination or to allow leak detection between circuits, since a failed plate or gasket can let fuel into cooling water or vice versa. There is no IMO convention specific to the plate exchanger type itself; requirements come through the classification society's machinery rules for the system the exchanger is part of.

Typical faults

What to look for in a supplier

• Material certificates for plates matching the actual fluid, especially titanium confirmation for seawater duty.
• Gasket compound datasheet matching the fluid and maximum operating temperature, not a generic default.
• Availability of individual replacement plates and gaskets for the exact plate pattern, since plate packs are not interchangeable between makers.

Before reassembling a gasketed plate exchanger after cleaning, check the plates go back in the original sequence and orientation - a swapped plate changes the flow pattern and the unit can look assembled correctly while badly underperforming.