HOT DI WATER MATERIALS OF CONSTRUCTION SEMICONDUCTORS

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Abstract

The plate heat exchanger (PHE) is often used in high-purity water applications. The design has been around for more than a century, and was originally used to pasteurize milk. For most of the same reasons that they work well for the dairy industry, they also work in many high-purity water applications. Gasketed PHEs can be pre-cleaned prior to assembly, periodically disassembled and cleaned, and are expandable as heat transfer demands increase. There are a variety of materials available for heat transfer plates. These range from low-grade austenitic stainless steel like 304 to graphite, which is used in strongly acidic applications. For decades the heat transfer plates in PHEs placed in high-purity water service were produced using austenitic stainless steel. The grade of choice was normally 316L; selected for its corrosion resistance and resistance to sensitization. The 316L was passivated to ensure a sufficient layer of pure chromium oxide (Cr2O3) on the surface of the material. As long as that passive chromium oxide layer was not breeched or depleted, the material performed well. Theoretically, stainless steel will provide adequate strength, heat transfer, and corrosion resistance in high-purity water applications.

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