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Quotes - Engineering - SalesEngineering Reference
Why marine coolers fail and how to stop it
A marine heat exchanger is a corrosion problem with a heat transfer job attached. The thermal side is well understood and rarely the reason a cooler comes out of a vessel. What takes them out is seawater: chloride attack on the wrong alloy, galvanic current between dissimilar metals bolted together, erosion at the tube inlets where the water turns into the bundle, and scale that quietly halves the surface. These pages set out what we have learned selling and rebuilding these coolers, in the order an engineer actually meets the problems.
The Materials pages cover the alloys that survive raw seawater and the ones that do not. Copper-nickel in its 90/10 and 70/30 grades carries almost every jacket water cooler we ship, titanium goes in where the water is dirty, hot, chlorinated or stagnant, and bronze and brass do the structural work at the bonnets and tubesheets. The stainless steel page explains a failure mode that surprises people, because 316 behaves beautifully in flowing seawater and pits through in a week of layup.
Corrosion Control, Selection and Service take it from there. Zinc anodes are the cheapest insurance on a vessel and the most commonly neglected item on it. Velocity limits decide whether a bundle lasts fifteen years or eighteen months. Sizing comes off the engine data sheet, not off a rule of thumb. And when a cooler is already installed and running warm, the diagnosis usually comes down to four or five checks that anyone with a thermometer and a pressure gauge can make.
Selection Support
What a Replacement Enquiry Needs
1.
Materials That Survive Seawater
Copper-nickel earns its place because it forms a tight protective film in seawater, resists biofouling in a way stainless does not, and costs a fraction of the exotic alloys. The 90/10 grade handles the great majority of jacket water and oil cooling duty; 70/30 buys more margin on velocity and on warmer or more polluted water. Both are available as the CN tube option on the frames we build.
Titanium is immune to seawater corrosion in any concentration or temperature we meet on a vessel, and where the duty justifies it we fit titanium tubes or supply a full titanium exchanger. The honest comparison is on our titanium vs copper-nickel page, which sets out the water conditions that make titanium the right answer and the far more common ones where copper-nickel remains the economical choice.
2.
Keeping The Corrosion Cell Closed
A shell and tube cooler in seawater is a working galvanic cell whether you designed it that way or not. Bronze bonnets, a brass tubesheet, copper-nickel tubes, a steel shell and whatever the piping is made of all sit in the same electrolyte. Zinc anodes in the bonnets are what keep the current flowing out of the sacrificial metal rather than out of the tube ends.
Velocity is the other half. Copper-nickel has a real erosion threshold, and running the tube side too fast strips the protective film at the inlet where turbulence is worst. That is why a bundle that failed in two years is usually telling you about a pump or a pass arrangement, not about metal quality. Both subjects have their own pages under Corrosion Control.
3.
Selecting And Replacing Coolers
A jacket water cooler is sized from heat rejection, and heat rejection comes off the engine data sheet at the rating you actually run. Horsepower alone gives a first cut and we use it to bracket a frame, but the confirmed selection needs the rejection figure, the seawater inlet temperature you design to, and the flows available on both sides. The sizing page shows how the numbers connect.
Most of what we ship is a replacement for something already on the vessel. That means working from a nameplate, a set of measurements, or a discontinued part number. We cross ITT Standard BCF and marine coolers into the B, HC and AB frames every week, and where the original is unmarked we take it from shell diameter, tube length, connection sizes and mounting centres.
Service, Cleaning And Diagnosis
A cooler running warm is not automatically undersized. Scale on the seawater side, an air pocket at the top of the shell, a partly blocked strainer, a bypassing thermostat and a tired pump all produce the same symptom. The Service pages walk through the checks in the order that costs least, and only then get to pulling the bundle.
When the bundle does have to come out, the decision is repair or replace. Plugging a few leaking tubes buys time and costs a little capacity; a bundle with general wall loss or inlet erosion across many tubes is finished. We supply replacement bundles, bonnets, gaskets and anodes for the frames we sell, so a rebuild does not have to mean a new shell.
Seawater Decides Everything
Choose the tube alloy for the water you actually have, not the water in the brochure, and the rest of the cooler will look after itself.
None of this is theory for its own sake. We build these coolers to order in the B, HC and AB frames with copper-nickel tubes, bronze bonnets and zinc anodes, and we replace bundles and anodes for vessels that already have them. If a page here raises a question about your installation, send us the nameplate and we will answer it against a real selection.
Engineering Topics
APPLICATIONS • JACKET WATER
HC Series
Marine jacket water coolers from 10 HP to about 1250 HP
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APPLICATIONS • SEAWATER
Raw Water Cooling
How raw seawater circuits are arranged and what they demand
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HEAT EXCHANGERS • PROTECTION
Zinc Anodes
Replacement anodes and plugs for the frames we supply
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