Marine and Transport

Standing seawater is harder on the plates than flowing seawater. With the pump off, the water in the channels warms, marine growth settles, and chlorides concentrate under the deposits - the conditions where pitting starts, even on a high-molybdenum plate that copes well in service.

Flush the seawater side with fresh water whenever the vessel or plant is going to stand, and drain and blow it out for a long lay-up. In a cold climate the same trapped water freezes, and water freezing in the channels can split a unit. A cooler that gave years of service and failed after one winter alongside usually failed this way.

The warmest water the vessel will operate in, with the engine at full load. That is the condition with the least temperature difference to work with, and a cooler sized on home-port conditions runs out of capacity in warmer water.

Sizing for the worst case leaves the cooler oversized everywhere else, and jacket water must not be over-cooled. Handle that with a thermostatic bypass on the jacket side. Throttling the seawater instead lowers its velocity in the channels, which invites fouling in a pack that cannot be opened.

The full nameplate designation, the classification society if the installation is classed, and a note of what the unit cools against. The material code deserves a second look: SC means 316 plates, and an SC unit that has pitted through on seawater should be replaced with an MC unit, not another SC.

State the class requirement at the start so the quote is for a unit carrying that approval. Dimensions and connection positions matter more aboard than ashore, because the pipework is rigid and the space is fixed - include a photo of the connection face. Availability is confirmed with the quote.

A central loop is usually the better arrangement for brazed units. One seawater-to-fresh-water exchanger in SMO 254 takes the chloride duty, and everything downstream - lube oil, hydraulic oil, refrigeration condensers - is cooled by treated fresh water and can use standard 316 plates.

The cost is one more temperature step, since each cooler now works against water slightly warmer than the sea, plus a circulating pump. In return, seawater, its strainer and its maintenance are confined to a single unit. Approach matters most on that central cooler, so expect a higher plate count there than on the coolers it serves.

Protection from pressure spikes and from the machine's own movement. Mobile hydraulics see sharp transients every time a valve shifts or a cylinder bottoms out, and pulsation fatigues braze joints even when the peak stays inside the rating. Put the cooler in the low-pressure return or in an off-line cooling loop, never in a working pressure line.

Connect it with flexible hoses, bracket it to the chassis independently of them, and add a bypass so cold, thick oil at start-up is not forced through the pack. The L class, at 14 bar and 225 C, is chosen here for its temperature rating - which is exactly why the cooler has to be kept out of the high-pressure side.