Marine and Seawater Heat Exchanger Buying Checklist: Copper-Nickel, Titanium, Duplex Steel, Filtration and Maintenance
When buying a seawater heat exchanger, look at heat transfer area, materials and operating limits together. Chlorides, dissolved oxygen, pollutants, sand, biofouling, stagnant water, flow velocity and dissimilar metal combinations all affect corrosion and service life. For heat exchangers on ships, offshore platforms, desalination plants, coastal factories and port facilities, material selection and maintenance often matter more than the purchase price.
The product catalog on this site includes gasketed plate heat exchangers, wide-gap welded plate heat exchangers and shell-and-tube heat exchangers. If your project involves seawater or high-chloride cooling water, state the seawater conditions, filtration, preferred materials and commissioning requirements clearly in the RFQ form.
1. Describe the Seawater Conditions First
At a minimum, state the seawater source, temperature range, chloride level, sand content, any pollutants, biofouling, filtration rating, design velocity, whether the unit will stand idle for long periods, whether it is drained regularly, whether cathodic protection is used, and whether the unit is installed on board or onshore. Without this data, suppliers can only recommend materials from experience, which is risky.
| Data | Why it matters |
|---|---|
| Seawater temperature | Affects corrosion and heat transfer |
| Stagnation time | Stagnant seawater can increase the risk of local corrosion |
| Filtration | Reduces blockage and erosion of tubes or channels |
| Velocity | Too low causes deposits; too high can erode the protective film |
| Material combination | Dissimilar metals can cause galvanic corrosion |
| Commissioning | Forming the initial protective film depends on water quality and operation |
2. What Copper-Nickel Can and Cannot Do
Nickel Institute material on the corrosion resistance of copper-nickel alloys explains that 90-10 and 70-30 copper-nickel rely on a protective surface film formed with seawater, and that initial exposure to clean, oxygenated seawater is important for forming a good film. Copper Development Association material also says that copper alloy tubes need to form a protective layer on the water side in clean, oxygenated seawater, and stresses that polluted water, water containing solids or other unfavorable conditions can lead to corrosion problems.
In other words, copper-nickel does not "never corrode". It is a material that needs correct commissioning, velocity control and water quality management. Ask suppliers about the recommended alloy, velocity range, filtration, commissioning, draining during shutdowns and how dissimilar metals will be joined.
3. Titanium and Stainless Steel Are Not Universal Answers Either
Titanium has strong corrosion resistance in many seawater applications, but watch for galvanic effects when it is combined with copper alloys, carbon steel or other materials. Copper Development Association guidance on material selection notes that strainers are used to reduce blockage and fouling of heat exchanger tubes, and it discusses galvanic corrosion when titanium tubes are combined with copper-based water boxes and tubesheets. Duplex, super duplex and high-nickel alloys also need to be judged against temperature, chlorides, crevices, welding and cost.
4. Filtration and Maintenance Are Part of Material Selection
In a seawater system, strainers, basket filters, backwash filters, cleaning connections and drains are not optional extras. Sand, shellfish, seaweed, plastic debris and biofouling can block pipes or plate channels. With the wrong filter, even an expensive material cannot keep the unit running reliably. Ask suppliers whether they recommend upstream filtration, whether the unit needs to be opened for inspection, whether it can be cleaned chemically and whether anti-fouling measures are needed.
5. Seawater Points to Check by Heat Exchanger Type
| Type | What to check |
|---|---|
| Shell-and-tube seawater cooler | Tube material, tubesheet, water boxes, filtration, mechanical cleaning |
| Gasketed plate heat exchanger | Plate material, gaskets, opening for cleaning, chlorides |
| Brazed plate heat exchanger | Materials and the risk of a unit that cannot be opened for cleaning |
| Welded plate heat exchanger | Welds, materials, CIP, channel blockage |
| Air-cooled alternative | If seawater maintenance costs are high, consider air cooling |
6. Questions to Ask Suppliers
Ask suppliers why they recommend the material, whether they have handled similar seawater duties, what filtration is required, how commissioning and shutdowns should be handled, whether there is a risk of galvanic corrosion between dissimilar metals, how the cleaning interval is decided, how material certificates and pressure test records will be provided, and whether they can supply maintenance instructions. If a supplier only says "titanium is best" or "316L is enough" but cannot explain the limits, expect more technical clarification later.
7. What This Means for Buyers
The key to buying a seawater heat exchanger is to judge material selection, filtration, commissioning, shutdowns, cleaning and supplier experience together. Copper-nickel, titanium, duplex steel and other materials can each suit some duties, and each can fail with the wrong water quality, stagnation, velocity or material combination. Submitting the seawater conditions and project limits through the RFQ form helps suppliers give more accurate advice on materials and design.
8. State the Actual Corrosion Conditions of a Seawater Project
Corrosion risk in seawater systems comes from chlorides, biofouling, velocity, temperature, sand, pollutants, stagnant water and galvanic corrosion. Writing only "seawater" or "marine use" is usually not enough. State whether it is an open seawater system, a closed cooling loop, a ship's central cooling system, desalination, a nearshore intake or an aquaculture or industrial seawater system. Also give the seawater temperature, sand content, whether there is filtration, whether the unit is cleaned regularly and whether water is left standing during long shutdowns. Material and design choices vary considerably between these conditions.
The Nickel Institute and the Copper Development Association both publish material on copper-nickel alloys and on material selection for seawater systems. Buyers can use it as background for discussing materials, but the final material still has to be confirmed against the project specification, the operating conditions and the supplier's engineering judgement. Titanium, copper-nickel, stainless steel, duplex steel, coatings and non-metallic parts are all commonly discussed, but none should be chosen without considering temperature, velocity, pollution and cost.
9. Ask Suppliers to State Their Corrosion Assumptions in the RFQ
A seawater heat exchanger supplier should be able to state the recommended material, the assumptions behind it, the cleaning method, filtration requirements, assumed velocity or pressure drop limits, whether sacrificial anodes are needed, whether there is a galvanic corrosion risk, shutdown and maintenance advice and a spare parts plan. For gasketed plate units, confirm the gasket and plate materials; for shell-and-tube units, confirm the tubes, tubesheet, shell, coatings and connections; for welded plate or wide-gap units, confirm the cleaning method and blockage risk.
10. Submit Site Photos and Water Analysis Together
Seawater projects depend heavily on site conditions. When replacing an old unit, upload photos of the old unit, its nameplate, where it corroded or leaked, cleaning records and a water analysis. For a new project, upload the process flow diagram, installation location, filtration plan and material specification. In the notes of the RFQ form you can write: "Please list the basis for your material selection, your corrosion assumptions, cleaning and maintenance recommendations and conditions where the design is not suitable." This makes suppliers answer more carefully and helps you spot quotes that only make general promises.
11. Set Out Material Recommendations and Responsibilities Clearly
Material selection for seawater heat exchangers often involves supplier advice, the engineering company's specification and the requirements of a classification society or the owner. Avoid a vague line such as "the supplier is responsible for material suitability". A clearer approach is this: the buyer provides water quality, temperature, velocity, filtration, operating mode and project specification; the supplier proposes materials and states the conditions where they are not suitable based on that data; and the final material is confirmed by the technical side and written into the order. This makes responsibilities clear and stops suppliers from over-promising when data is incomplete.
At the quotation stage, you can also ask suppliers to list their maintenance assumptions, for example whether regular flushing is needed, whether stagnant water must be avoided, whether biofouling must be removed, and whether spare gaskets or a tube bundle inspection interval are recommended. For marine and offshore projects, transport vibration, salt spray, protective packing and access to spare parts should also be part of the decision. The real cost of seawater equipment is not only the purchase price but also long-term corrosion control and the risk of downtime.
Sources and Related Pages
- Nickel Institute on the seawater corrosion resistance of copper-nickel alloys: https://nickelinstitute.org/en/nickel-applications/copper-nickel-alloys/corrosion-resistance-of-copper-nickel-alloys/
- Copper Development Association on commissioning, shutdown and operation of seawater heat exchangers: https://www.copper.org/applications/marine/cuni/applications/seawater_system_design/heat_exchangers_piping/heat_exchangers_and_piping.html
- Copper Development Association on material selection for seawater systems: https://www.copper.org/applications/marine/cuni/applications/seawater_system_design/materials_selection.html
- HeatEx Direct gasketed plate heat exchangers: https://heatexdirect.com/products/shanghai-heat-transfer-equipment-co-ltd/gasketed-plate-heat-exchanger
- HeatEx Direct wide-gap welded plate heat exchangers: https://heatexdirect.com/products/shanghai-heat-transfer-equipment-co-ltd/wide-gap-welded-plate-heat-exchanger
- HeatEx Direct shell-and-tube heat exchangers: https://heatexdirect.com/products/siping-viex-heat-exchange-equipment-co-ltd/tubular-heat-exchanger