Material of Construction of plate Heat Exchanger
he Material of Construction (MOC) for a plate heat exchanger is a critical selection criterion that directly impacts its performance, longevity, and suitability for a specific application. The choice depends on the fluids being used, their temperatures, concentrations, and operating pressures.
The main components to consider are the plates and the gaskets (for gasketed types) or the brazing material (for brazed types).
1. Plate Materials
The plates are typically made from stainless steel due to its excellent balance of corrosion resistance, strength, and cost. However, more exotic alloys are used for highly corrosive applications.
| Material | Typical Grade | Key Properties | Common Applications |
| Stainless Steel | AISI 304 / 1.4301 | Good general corrosion resistance, cost-effective. | Most common material. Water (city, river, cooling tower), oils, mild chemicals. |
| Stainless Steel | AISI 316 / 1.4401 | Superior corrosion resistance due to addition of Molybdenum. Resists chlorides and acids better than 304. | Standard for industrial & seawater applications. Cooling tower water, brackish water, food processing, chemicals. |
| Stainless Steel | 316Ti / 321 (Titanium stabilized) | Resists chloride stress corrosion cracking at higher temperatures. | Applications with high chloride content and high temperatures. |
| Titanium | Grade 1 | Excellent corrosion resistance, especially to chlorides (seawater) and oxidizing acids. | Seawater cooling, chlorinated water, aqua regia, other highly corrosive media. |
| Titanium-Palladium | Grade 7 / 11 | Even higher corrosion resistance than pure titanium, especially in reducing acids. | More aggressive chemical environments than pure titanium can handle. |
| Hastelloy® | C-22 / C-276 | Exceptional resistance to a wide range of severe corrosive chemicals, including chlorides and sulfuric acid. | Extreme chemical applications in chemical processing, pharmaceuticals, and pickling acids. |
| Nickel | Alloy 200 / 201 | Good resistance to caustic solutions and high temperatures. | Hot concentrated caustic soda (NaOH) applications. |
| Inconel® | 625 | High strength and excellent resistance to pitting, crevice corrosion, and high temperatures. | High-temperature water, flue gas cleaning, harsh chemical processes. |
| Graphite | Impervious Graphite | Excellent resistance to almost all acids (except strong oxidizing acids). | Highly corrosive acid services where metal alloys are not suitable. |
2. Gasket Materials (for Gasketed PHEs)
The gasket material must be compatible with the fluid, temperature, and must provide a good seal.
| Material | Max Temp (Approx.) | Key Properties | Common Applications |
| Nitrile (NBR) | 110°C – 130°C | Most common. Good resistance to oils, fats, water, aliphatic hydrocarbons. | Water, seawater, oils, brines, dairy. General purpose. |
| EPDM (Ethylene Propylene) | 150°C – 170°C | Excellent resistance to hot water, steam, acids, alkalis, and polar solvents. Poor resistance to oils and fuels. | Hot water/steam (heating circuits), acids (e.g., HCl, H₂SO₄), caustics, alcohols. |
| Viton® (FKM) | 180°C – 230°C | Excellent resistance to high temperatures, oils, fuels, acids, and aliphatic and aromatic hydrocarbons. Expensive. | High-temperature applications, aggressive chemicals, refined oils, chlorinated solvents. |
| Compressed Asbestos-Free (CAF) | 200°C – 260°C | High temperature and pressure resistance. Used for special severe service. | Superheated water, steam, and high-temperature oils. |
3. Brazing Materials (for Brazed PHEs – BPHEs)
For brazed plate heat exchangers, the brazing alloy that fuses the plates together is a critical material choice.
| Material | Key Properties | Fluid Compatibility |
| Copper (Cu) | Most common. Excellent brazing properties and thermal conductivity. | Compatible with standard refrigerants (R134a, R410A, R407C), water, oils. Not compatible with ammonia (R717) or corrosive media that attack copper. |
| Nickel (Ni) | More corrosion resistant than copper but more expensive and requires higher brazing temperatures. | Required for ammonia (R717) refrigeration. Also used with corrosive fluids, seawater, and certain chemicals. |